Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Physics  (10,640)
  • Rehabilitation
  • Strömungsmechanik
  • Wiley-Blackwell  (10,647)
  • Sage Publications  (6)
  • American Institute of Physics (AIP)  (2)
Collection
Years
  • 1
    ISSN: 0887-6266
    Keywords: polyimides ; reflectivity ; moisture absorption ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Water absorption in thin films (〈1000 Å) of a commercial polyimide was evaluated by monitoring dimensional changes induced by a humid environment. Film thickness was measured using x-ray reflectivity, which is a nondestructive technique offering angstrom resolution in the measurements of thin film or multilayer thickness. The effect of several variables on the absorption of moisture were monitored in polyimide films adhered to polished silicon substrates, including total dry film thickness, exposure time, and the contribution of a coupling agent. The percentage increase in film thickness due to moisture uptake is found to be a weak function of dry film thickness, decreasing as dry film thickness increases, and to be somewhat affected by the use of an interfacial coupling agent. The observed behavior points to the polymer/substrate interface as a strong factor controlling the absorption of moisture in the polyimide/silicon system, and is believed to reflect the presence of a highly moisture-saturated interfacial layer. A bilayer model is proposed, and the feasibility of using this model to describe the observed behavior is considered. Published 1998 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America. J Polym Sci B: Polym Phys 36: 155-162, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: integral sorption ; rubbery polymers ; moving boundaries ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Simple equations are derived that describe integral sorption and desorption experiments under conditions where moving boundary effects in polymer films and spheres can be large because of high solvent concentrations. General conclusions are formulated about the nature of sorption and desorption experiments for both rectangular and spherical geometries. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 171-180, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0887-6266
    Keywords: tetramethyl bisphenol-A polyarylate ; aliphatic polyester ; blend ; miscibility ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior of blends of tetramethyl bisphenol-A polyarylate (TMPAr) with various linear aliphatic polyesters characterized by the ratio of aliphatic carbons to ester groups in the repeating unit, CH2/COO = 3 ∼ 9, was examined by differential scanning calorimetry and dynamic mechanical analysis. TMPAr/aliphatic polyester blends prepared by solvent casting were found to be miscible when the CH2/COO ratio of aliphatic polyesters was larger than 4 and up to 9. The thermodynamic interaction parameter, B for the miscible blends was determined by the analysis of the depression of the melting point of polyester using the Hoffman-Weeks method. From the analysis of the heat of mixing data using a binary interaction model, it was concluded that strong unfavorable intramolecular interaction exists between the —CH2— and —COO— units in aliphatic polyesters and that four substituted methyl groups produces more favorable effects on the miscibility TMPAr with aliphatic polyesters. © 1998 John Wiley & Sons, Inc. J Polym Sci 36: 201-212, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0887-6266
    Keywords: entangled polymer solution ; double-step strain rate ; flow birefringence ; tube model ; segmental stretch ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Experiments measuring the orientation angle and birefringence in startup and double-step strain rate flows were conducted on a 3.0 wt % 8.42 × 106 molecular weight polystyrene solution in a Couette flow cell. A phase-modulated flow birefringence apparatus was used to noninvasively probe the sample. Upon startup from rest, the orientation angle undershoots its final steady-state value, as seen by earlier investigators. When the shear rate undergoes a step increase from one nonzero value to another, the amplitude of this undershoot is decreased. However, a more significant effect is a shorter time scale overshoot in the orientation angle that is highly counterintuitive in the sense that an increase of shear rate initially produces a rotation of chain segments away from the flow direction. Similarly, a step decrease in shear rate yields an initial transient rotation toward the flow direction. In both cases, the height of the peaks depends upon the magnitude of the shear rate jump, and the width of the peaks is a function of the final shear rate. The longer time transients in the startup and step increase experiments reflect an apparent change in the relaxation time for segment orientation, which we tentatively attribute to a combination of tube dilation and convective constraint release. The shorter time scale over- and undershoots in the orientation angle appear to be qualitatively explained by considering the differences in extension or contraction of segments along the polymer chain. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 265-280, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0887-6266
    Keywords: side-chain liquid-crystalline polymer membrane ; pervaporation ; benzene/cyclohexane mixture ; state-transformation ; benzene permselectivity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 281-288, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0887-6266
    Keywords: polydimethylsiloxane ; permeability ; sorption ; mixed gas permeation ; clustering ; acetone/nitrogen separation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The permeability of polydimethylsiloxane [PDMS] to acetone, nitrogen, and acetone/nitrogen mixtures has been determined at 28°C. In pure gas experiments, the permeability of PDMS to nitrogen was 245 × 10-10 cm3(STP) · cm/cm2 · s · cmHg and was independent of pressure. The permeability of PDMS to acetone vapor increased exponentially with increasing acetone pressure. PDMS is much more permeable to acetone than to nitrogen; acetone/nitrogen selectivity increases from 85 to 185 as acetone partial pressure in the feed increases from 0 to 67% of saturation. In mixed gas permeation experiments, the nitrogen permeability coefficient is independent of acetone relative pressure and is equal to the pure gas permeability coefficient. The acetone permeability coefficient has the same value in both mixed gas and pure acetone permeation experiments. Average acetone diffusivity in PDMS, determined as the ratio of permeability to solubility, decreases with increasing acetone concentration due to mild clustering of acetone in the polymer (because acetone is a poor solvent for PDMS) and changes in the polymer-penetrant thermodynamic interactions which influence diffusion coefficients. A Zimm-Lundberg analysis of the acetone sorption isotherm is also consistent with acetone clustering in PDMS. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 289-301, 1998
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0887-6266
    Keywords: pressure-sensitive adhesive ; PSA ; tackifier ; tack adhesion ; polyisoprene ; poly(ethylene-propylene) ; pulsed gradient spin echo-nuclear magnetic resonance ; PGSE-NMR ; diffusion ; n-butyl ester of abietic acid ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A detailed study of the mobility of a tackifying resin in a pressure-sensitive adhesive (PSA) has been done for the first time. The objective of this work is to relate changes in adhesive performance with tackifier loading to tackifier mobility. Tackifiers are low-molecular weight resins that improve the overall performance of PSAs. They increase the adhesive tack or the ability to form a bond of measurable strength after brief contact under slight applied pressure. In this study the diffusion of n-butyl ester of abietic acid (n-BEAA) in either polyisoprene (PI) (Mw = 195,000 Mw/Mn ∼ 1.05) or poly(ethylene-propylene) (PEP) (Mw = 40,000 Mw/Mn ∼ 2.30) was measured by Pulsed Gradient Spin Echo-Nuclear Magnetic Resonance (PGSE-NMR) as a function of both tackifier concentration and temperature. The concentration dependence of the tackifier's diffusion coefficient was weak for both systems. The weak variation in mobility with composition for the PI/n-BEAA system was consistent with that system's weak variation in tack with composition. On the other hand, blends of PEP/n-BEAA showed only modest variation in mobility, even though these adhesive systems showed appreciable enhancement of tack at intermediate compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 373-381, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0887-6266
    Keywords: syndiotactic polypropylene ; form-IV ; form II ; kink bands ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The packing of the chains in (T6G2T2G2)n conformation of the form IV of s-PP is revisited on the basis of packing energy and structure factor calculations. According to this analysis, an alternative mode of packing has been suggested. A monoclinic structural model, with the unit cell centered on the C face, is obtained, after small changes of the atomic coordinates in the triclinic structural model as proposed by Chatani et al. The monoclinic model presents a lower packing energy than the triclinic model and a good agreement between the calculated and observed structure factors. The triclinic structural model implies that all the chains are rotated by the same amount around the chain axis with respect to the monoclinic structural model. Since clockwise and counter clockwise rotations are equivalent, the monoclinic structural model may be taken as descriptive of the order in the long range, for the form IV of s-PP, or in other terms, descriptive of an average structure (space group C2, unit cell constants equal to am = 14.17 Å, bm = 5.72 Å, cm = 11.6 Å, and βm = 108.8°). The triclinic structural model for this polymorph, instead (space group P1, unit cell constants equal to at = 5.72 Å, bt = 7.64 Å, ct = 11.60 Å, αt = 73.1°, βt = 88.8°, γt = 112.0°) is probably more properly descriptive of local situation of order (the symmetry, locally, is broken). Analogies between the monoclinic limit ordered structural model for the form IV and the orthorhombic limit ordered structural model for the form II (with chains in the more stable (TTGG)n conformation) of s-PP are also provided. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 395-402, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 0887-6266
    Keywords: ion-selective membranes ; gel crystallization ; poly(siloxanes) ; crown-ethers ; calixarenes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A one-step procedure for the preparation of ion-selective membranes is described. The method employs the thermally induced gel crystallization of ultrahigh molecular weight poly(ethylene) (UHMW-PE) from a dilute xylene solution. After evaporation of the xylene, a microporous UHMW-PE film remains, which can serve as the support for liquid and polymeric ion-selective membranes. The addition of a membrane solvent and suitable receptor molecules to the xylene solution allows a one-step incorporation of these membrane components into the UHMW-PE support. The influence of the preparation conditions of the UHMW-PE support on the rates of the p-tert-butylcalix[4]arene tetraethylester-mediated transport of NaClO4 was studied. Two concepts to improve the life-time of the membranes are introduced. In a first approach, the addition of photocrosslinkable nitril-substituted siloxane copolymers to the membrane phase has been evaluated. The enhanced viscosity of the membrane phase reduces leaching of carrier and solvent molecules from the membrane into the aqueous phases. In a second approach, the solvent is omitted and the membrane-phase merely consists of a benzo-15-crown-5 or calix[4]arene modified siloxane-copolymer, which is substituted to such a degree that ion transport no longer has to take place via diffusion of host-guest complexes but by jumping of the cations from one fixed carrier to a neighboring carrier. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 383-394, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0887-6266
    Keywords: P(VDF/TrFE) copolymer ; phase transition ; ferroelectric ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A systematic study was carried out on the effect of the crystallization temperature (Tcr), on the phase transitions presented by P(VDF/TrFE) copolymers cast from dimethylformamide (DMF) solution with molar ratios 60/40, 70/30, and 80/20. The results obtained by differential scanning calorimetry (DSC) showed that two-phase transitions are observed only when the copolymer crystallizes above a certain temperature To, and that the temperatures at which these transitions occur are reduced slightly with Tcr increase. It also was observed that when Tcr increases, the intensity of the endotherm corresponding to the lowest temperature transition is increased, whereas the one corresponding to the highest temperature transition is reduced. In order to explain these phenomena, the existence of two ferroelectric and two paraelectric phases is suggested. The conformational differences between like phases occur due to the distinct origin of each one: the best organized phase crystallizes directly from solution, whereas the least organized is the result of a solid phase transition. Wide angle x-ray diffusion (WAXD) diffractograms corroborate this hypothesis. Phase diagrams for samples crystallized below and above To have been proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 403-414, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 11
    ISSN: 0887-6266
    Keywords: block copolymer ; polymeric micelle ; nanoparticle ; clonazepam ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Block copolymers consisting of poly(γ-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part were synthesized and characterized. Core shell type nanoparticles of the block copolymers (abbreviated GEG) were prepared by the dialysis method. Under fluorescence spectroscopy measurement, the GEG block copolymers were associated in water to form core shell type nanoparticles as polymeric micelles and the critical micelle concentrations (CMC) values of the block copolymers decreased with increasing PBLG chain length in the block copolymers. Transmission electron microscopy (TEM) observations revealed nanoparticles of spherical shapes. From dynamic light scattering (DLS) study, sizes of nanoparticles of GEG-1 and GEG-2 copolymer were 64.3 ± 28.7 nm and 28.9 ± 7.0 nm. The drug-loading contents of GEG-1 and GEG-2 nanoparticles were 15.2 and 8.3 wt %, respectively. These results indicated that the drug-loading contents were dependent on PBLG chain length in the copolymer. Then, the longer the PBLG chain length, the more the drug-loading contents. Release of clonazepam (CNZ) from the nanoparticles was slower in higher loading contents of CNZ than lower loading contents due to the hydrophobic interaction between PBLG core and CNZ. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 415-423, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0887-6266
    Keywords: poly(arylene ether ketone) ; gas permeability ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work we present the results from studies on novel poly(arylene ether ketone)s, including gas permeability, wide-angle x-ray diffraction (WAXD), and dynamic mechanical analysis (DMA). Poly(arylene ether ketone)s containing 2,2′- and 3,3′-dibenzoylbiphenyl (DBBP) moieties were characterized to study the effect of biphenyl substitution on gas transport properties. Gas permeabilities of naphthalene-containing poly(arylene ether ketone)s were also measured. Higher permeabilities were observed for polymers prepared with 6F-BPA, compared to 9,9-bis(4-hydroxyphenyl)fluorene (HPF). The naphthalene-containing polymers exhibited higher permeabilities than the DBBP polymers, except for a polymer having the 2,2′-DBBP and tetramethylbiphenyl moieties. Based on our work, and results reported in the literature, the 3,3′-DBBP polymers showed the lowest permeabilities for DBBP-containing poly-(arylene ether ketone)s. The low permeabilities are due to more efficiently packed chains brought on by greater flexibility of the backbone, compared to the other polymers studied. DMA studies confirmed the higher barriers to rotation which are believed to be responsible for 2,2′-DBBP polymers having similar selectivities compared to 3,3′-DBBP polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 425-431, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 0887-6266
    Keywords: cholesteric order ; electron microscopy ; periodical lamellar structure ; macromolecules ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The macromolecular cholesteric structure in the ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid [AA] cholesteric liquid crystalline solutions is studied by directly observing the morphology and structure of the ethyl-cyanoethyl cellulose [(E-CE)C]/polyacrylic acid [PAA] using electron microscopy. A periodical lamellar structure is observed in ultrathin slices of the composites with cholesteric order by both transmission electron microscopy (TEM) and low-voltage scanning electron microscopy (LVSEM). It is suggested that the periodical lamellar structure is induced by the twist of the molecular orientation in the cholesteric phase and reflects the structural features of the macromolecular cholesteric phase. The macromolecular cholesteric phase exhibits the twisted ring morphology in the initial stage of the formation of the liquid crystalline phase. The swelling of the ultrathin slices with cholesteric order in water is heterogeneous, which suggests the tight packing of the (E-CE)C chains in the direction of the helix axis in the macromolecular cholesteric phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 439-445, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 0887-6266
    Keywords: polyethylene terephthalate ; low density polyethylene ; isocyanate functional group ; compatibility ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To evaluate the compatibilizing effects of isocyanate (NCO) functional group on the polyethylene terephthalate/low density polyethylene (PET/LDPE) blends, LDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared and blended with PET. The chemical reaction occurred during the melt blending in the PET/LDPE-g-HI blends was confirmed by the result of IR spectra. In the light of the blend morphology, the dispersions of the PET/LDPE-g-HI blends were very fine over the PET/LDPE blends. DSC thermograms indicated that PET microdispersions produced by the slow cooling of the PET/LDPE-g-HI blends were largely amorphous, with low crystallinity, due to the chemical bonding. The tensile strengths of the PET/LDPE-g-HI blends were higher than those of the PET/LDPE blends having a poor adhesion. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 447-453, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 0887-6266
    Keywords: liquid-crystalline ; polymers ; network ; fibers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Preliminary results on the synthesis and characterization of anisotropic networks, oriented on a macroscopic scale, are reported. Fiber samples of segmented thermotropic liquid-crystalline polymers bearing the oxypentenyl lateral substituent have been crosslinked via thermally activated radical reaction. This was made possible by immersion of fiber samples in dichloromethane containing t-butylperoxybenzoate as activating agent, thus allowing its diffusion in the samples. Subsequent annealing at 145°C brings us to an anisotropic network with no loss of the original orientation. A mesophase is stabilized and no structural modification is observed by heating samples from room temperature up to 400°C, where thermal decomposition takes place. Crosslinked fibers exhibit good tensile properties, at both room temperature and at 150°C. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 433-438, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 0887-6266
    Keywords: photoreactive polymer blends ; photocrosslinking kinetics ; photodimerization of anthracene ; Kohlrausch-Williams-Watts relaxation ; poly(vinyl methyl ether) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixtures of polystyrene derivatives (PSCS) and poly(vinyl methyl ether) (PVME) were made photocrosslinkable by chemically labeling PSCS chains with photoreactive anthracene. Miscibility of these anthracene-labeled PSCS/PVME blends was examined by light scattering under several crosslinking conditions in the one-phase region via photodimerization of anthracenes. As the reaction proceeds, the coexistence curve of PSCS/PVME blends shifts toward the low temperature side. By following the changes in concentration of anthracenes with irradiation time, it was found that the crosslinking reaction of PSCS chains in the blends does not follow the mean-field kinetics. However, it can be well expressed by the Kohlrausch-Williams-Watts (KWW) relaxation mechanism, indicating that the crosslinking reaction proceeds inhomogeneously in the blends. By scaling the reaction time with the average reaction rate obtained from the KWW equation modified for the reaction kinetics, all the crosslinking data obtained in the miscible region of the reacted blends fall on a single master curve. These experimental results suggest the universal behavior of the photocrosslinking kinetics obtained under the “shallow quench” conditions in the region far away from the coexistence curve of the reacting blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 455-462, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 0887-6266
    Keywords: hydrogel ; free volume ; positron annihilation ; water ; density ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A copolymer of 2-hydroxyethyl methacrylate (HEMA) with 2-ethoxy ethyl methacrylate (EEMA) was synthesized and the molecular mobility, free volume, and density properties examined as a function of composition. These properties were correlated with the equilibrium water uptake in order to determine which of the properties were most influential in causing high water sorption, as these materials are suitable candidates for hydrogel systems. It was found that the polar HEMA repeat unit results in a rigid, glassy sample at room temperature due to the high degree of hydrogen bonding between chains whereas high EEMA content leads to rubbery samples with subambient glass transition temperatures. The free volume properties on the molecular scale measured by positron annihilation lifetime spectroscopy (PALS) showed that higher HEMA content led to smaller, fewer holes and a lower free volume fraction than EEMA. Therefore the high water uptake of HEEMA-containing copolymers is largely related to the high polarity of the HEMA unit compared to EEMA, despite the low content of free volume into which the water can initially diffuse. Trends in density with copolymer composition, as measured on a macroscopic level, differs to that seen by PALS and indicates that the two techniques are measuring different scales of packing. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 463-471, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: crystallization ; polymer blends ; pattern formation ; numerical simulation ; syndiotactic polystyrene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The development of texture which exists in polymer spherulites grown from single phase melts containing an appreciable amount of noncrystallizable material was investigated. This texture generally consists of lamellar bundles separated by amorphous regions, both of which are typically 0.1-1 μm thick. A space-time finite element model previously developed by us was used to simulate the growth of a group of polymer lamellae. The model determines the impurity concentration field in the melt surrounding the growing lamellae and tracks the growth of each lamella. Important variables are the initial melt concentration of noncrystallizable material, the mass diffusion coefficient of noncrystallizable species, lamellar thickness, long period, and the rate of molecular attachment at the growth front. Under certain conditions, bundles did indeed develop during the simulations. These results were used to predict bundle thicknesses. The predictions of bundle texture were compared to actual textures observed in blends of syndiotactic and atactic polystyrene. It was found both experimentally and numerically that bundle thickness was a strong function of crystallization temperature and a relatively weak function of both the initial composition of noncrystallizable species and the degree of crystallinity of the lamellar stack. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 873-888, 1998
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 19
    ISSN: 0887-6266
    Keywords: activation volume ; relaxation ; pressure ; polymer ; reorientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume of 4-(diethylamino)-4′-nitrotolane (DEANT) in poly(methyl methacrylate) (PMMA). The decay of the SHG signal from films of DEANT/PMMA was recorded at hydrostatic pressures up to 3060 atm and at different temperatures between 25°C below the glass transition temperature to 35°C above it. The activation volume, ΔV*αβ associated with the long range α-type motion of the polymer remained constant at 213 ± 10 Å3 between Tg - 25°C and Tg + 10°C. At higher temperatures, ΔV*αβ decreased linearly with increasing temperature. The activation volume, ΔV*αβ, associated with short range secondary relaxations was constant over the entire temperature range with a value of 77 ± 10 Å3. The data suggest that above Tg chromophore reorientation is coupled to both the long range and local motions of the polymer; whereas, well below Tg chromophore reorientation is closely coupled to the local relaxations of the polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 901-911, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 0887-6266
    Keywords: glass transition ; thermally stimulated currents (TSC) ; relaxation ; PVC ; dielectric ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermally stimulated current-thermal sampling (TSC-TS) technique was used to study the broadened glass transition in conventional “atactic” poly(vinyl chloride), PVC. The activated parameters obtained from the TSC-TS data, mainly the apparent activation energy (Ea), characterize the breadth of glass transitions in a very sensitive way. These results are compared with those values of Ea obtained from the literature, using a recently proposed method of analyzing a.c. dielectric constants and their derivatives, over the temperature range of -100-130°C. Both techniques detect weak cooperative glass transition-like relaxations well below the main glass transition of ca. 80°C. As is the case with “atactic” PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 60°C below the main glass transition in atactic PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 913-918, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 21
    ISSN: 0887-6266
    Keywords: Pluronic P103 ; micellar formation and structure ; supramolecular structure ; laser light scattering ; small-angle X-ray scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Both laser light scattering (LLS) and small-angle X-ray scattering (SAXS) were used to study the water-induced formation and structure of micelles and supramolecules of Pluronic P103 [(EO)17(PO)60(EO)17] in o-xylene, a selective solvent for the long middle block. In pure o-xylene, P103 molecules exist as unimer coils with an equivalent hard-sphere radius of 1.6 nm even at fairly high concentrations. Micelles with a PEO/water core and a PPO dominated corona were formed in the presence of water when the P103 concentration ≥0.046 g/mL. The size and structure of micelles have been studied as a function of solubilized water content Z (the molar ratio of water to EO units) in micelles. The micelles change from a somewhat open structure with some EO units either dangling out of the micellar core or being incorporated into neighboring micellar cores at low Z values to a flower-like structure with relatively sharp interface at high Z values. At low Z values (〈 about 2.9), micelles tend to have a structure with part of the poorly solvated PEO blocks present in the corona. With more water added to the core, the PEO blocks in the corona gradually entered into the core, and the PPO blocks backfolded to form loops. With increasing Z, the micellar core radius, Rc, and the hard-sphere volume fraction, φ, of micelles increased; the aggregation number, N, kept nearly a constant; but the hydrodynamic radius, 〈Rh〉0, and the corona thickness, Rs, decreased. At high Z values (〉 about 2.9), micelles have a flower-like structure with the two end PEO blocks belonging to the small micellar core. With increasing Z, the values of Rc, φ, and N increased, while Rs kept nearly a constant. In the concentrated regime (C 〉 0.30 g/mL), a stiff polymer network at a critical φ value of 0.49 was formed. The supramolecular structures with a face-center cubic packing, and a possible hexagonal packing at higher polymer concentrations (i.e. 〉 0.55 g/mL), were observed, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 889-900, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 22
    ISSN: 0887-6266
    Keywords: potentiometric titration ; mathematical simulation ; neighbor effect ; interpolymer complexes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theory of the “neighbor effect” was applied for the description of the potentiometric titration curves of polyelectrolytes. Satisfactory results for poly(acrylic acid) were obtained by considering the effect of the two (at the right and at the left) nearest neighbors on the state of the monomeric unit in the limits of triads. The developed method was used for the determination of the degree of linkage of acidic groups in solutions of the interpolymer complexes. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 931-936, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 23
    ISSN: 0887-6266
    Keywords: thermodynamics ; heteropolymers ; phase diagram ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On the basis of a variational principle a quantitative theory is developed enabling a thermodynamic description in terms of mean field approximation of heteropolymer mixtures of macromolecules with an arbitrary distribution for both degree of polymerization and composition. Rather simple general equations are derived to calculate compositions and volume fractions of spatially homogeneous macroscopic phases as well as to find the cloud-point curve, spinodal, and critical points. Potentialities of general theory are illustrated for copolymers synthesized by traditional methods. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 937-958, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 24
    ISSN: 0887-6266
    Keywords: α-relaxation ; cold crystallization ; poly(aryl-ether-ether-ketone) (PEEK) ; poly(ether-imide) (PEI) ; vitrification ; devitrification ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have established time-temperature transformation and continuous-heating transformation diagrams for poly(ether-ether-ketone) (PEEK) and PEEK/poly(ether-imide) (PEI) blends, in order to analyze the effects of relaxation control on crystallization. Similar diagrams are widely used in the field of thermosetting resins. Upon crystallization, the glass transition temperature (Tg) of PEEK and PEEK/PEI blends is found to increase significantly. In the case of PEEK, the shift of the α-relaxation is due to the progressive constraining of amorphous regions by nearby crystals. This phenomenon results in the isothermal vitrification of PEEK during its latest crystallization stages for crystallization temperatures near the initial Tg of PEEK. However, vitrification/devitrification effects are found to be of minor importance for anisothermal crystallization, above 0.1°C/min heating rate. In the case of PEEK/PEI blends, amorphous regions are progressively enriched in PEI upon PEEK crystallization. This promotes a shift of the α-relaxation of these regions to higher temperatures, with a consequent vitrification of the material when crystallized below the Tg of PEI. The data obtained for the blends in anisothermal regimes allow one to detect a region in the (temperature/heating rate) plane where crystallization proceeds in the continuously close proximity of the glass transition (dynamic vitrification). These experimental findings are in agreement with simple simulations based on a modified Avrami model coupled with the Fox equation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 919-930, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 25
    ISSN: 0887-6266
    Keywords: positron annihilation ; free-volume ; Nafion ; free-volume size distribution ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report a new result of free-volume hole size distribution in water and ethanol-swollen Nafion-117 polymer. With the increase in water content, free-volume hole size decreases, but overall the volume fraction increases. The hole size distribution in dry polymer is seen to be distinctly different from hydrated membranes. The narrow and symmetric distribution in hydrated membrane as compared to dry membrane is believed to be a consequence of crosslinking due to cluster formation. In alcohol-swollen membranes, on the other hand, not only are the free-volume size and fraction seen to be higher, the hole size distribution is seen to be broader compared to dry or hydrated membranes, indicating the effect of penetration of alcohol into the hydrophobic backbone region. We have also examined our results vis-a-vis reported gas diffusion studies in Nafion in the framework of existing free-volume model. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 983-989, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 26
    ISSN: 0887-6266
    Keywords: poly(methylphenylsiloxane) ; poly(dimethylsiloxane) ; titania ; silica ; composites ; reinforced elastomers ; morphology ; stress-strain isotherms ; scattering intensities ; differential scanning calorimetry ; transmission electron microscopy ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The work reported in the preceding article in this series is extended by consideration of polysiloxane-ceramic composites based on atactic poly(methylphenylsiloxane) (PMPS) elastomers instead of poly(dimethylsiloxane). The former is noncrystallizable because of its stereochemically irregular structure, while the latter is crystallizable. In addition, some composites were prepared by the in situ precipitation of titania instead of silica. The resulting materials were characterized using differential scanning calorimetry, equilibrium stress-strain measurements in elongation, small-angle neutron scattering, and transmission electron microscopy. The moduli of the PMPS elastomers were found to increase significantly with increase in amount of either type of filler, with reinforcing upturns at high elongation in the case of the silica. Because the PMPS elastomers were amorphous, it is obvious that strain-induced crystallization is not required for these upturns in modulus. Titania did not give as good reinforcement as did silica, at least in the case of PMPS. Differences in interactions between the polymer and the two fillers are obviously important in this regard, but differences in particle morphology probably also contribute. Specifically, the titania “particles” were significantly larger than the silica particles when observed in TEM, and appeared to be much more porous. The actual domain size as measured by scattering, however, was only approximately 5% larger. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1191-1200, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 27
    ISSN: 0887-6266
    Keywords: FTIR spectroscopy ; isotactic polystyrene ; crystallization process ; induction period ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melt crystallization process of isotactic polystyrene (i-PS) was studied by means of in situ Fourier transform infrared (FTIR) spectroscopy, with a focus on the conformational changes during the induction period. The spectra obtained during the induction period suggested the occurrence of some ordered structure that is characterized by higher regularity and packing of the helical moieties than observed in the melt. This ordered structure was clearly different from the amorphous structure, and close to the crystal structure. The Avrami analysis indicated that the formation process of the ordered structure at the late stage of the induction period is similar to the growth process of the crystallites after the induction period. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1227-1233, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 28
    ISSN: 0887-6266
    Keywords: polyimides ; thin films ; infrared spectroscopy ; molecular structure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular structure of poly[biphenyl dianhydride-p-phenylenediamine] (BPDA-PDA) polyimide in ultrathin (3-300 nm) films on silicon has been characterized by polarized infrared spectroscopy in conjunction with ellipsometry and X-ray reflectivity measurements. In spite of the high degree of crystalline packing of the polymer chains, the results show that an unexpected and significant content of imide rings exhibit local structural perturbations, including out-of-plane twisting. Further, the fraction of perturbed rings increases with increasing film thickness while, in contrast, the high degree of in-plane uniaxial film symmetry and planar stacking of the chains remain constant with thickness. These results reveal a new structural aspect of localized ring disorder that arises within the otherwise well-ordered, chain-stacked structure of BPDA-PDA polyimide films. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1247-1260, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 29
    ISSN: 0887-6266
    Keywords: PMMA ; mechanical properties ; ionomer precursor polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rigid-rigid blends made of ionomer and ionomer precursor polymer, based on poly(methyl methacrylate) (PMMA), have been investigated. Two series of blends have been prepared for studying mechanical properties. In one series, dynamic mechanical properties were determined over a wide range of temperatures. As the weight fraction of the ionomer was increased, there was a modest increase of modulus at ambient temperature and a very large increase in the rubbery modulus at elevated temperatures above the glass transition temperature of PMMA. In a second series of tests, tensile stress-strain measurements, made at an ambient temperature, were carried out over a wide range of blend compositions. For all blends tested, the mechanical properties exhibited a synergistic enhancement, i.e., average values of modulus, strength and fracture energy were all higher than expected based on the rule of mixtures. Measurements of fracture toughness also exhibited synergy, with a maximum value, higher than the value of either blend component, being attained in blends containing about 30 wt % of the PMMA ionomer. These results are interpreted in terms of a higher resistance to fracture of the more chain-entangled ionomer phase and good interfacial adhesion between the two components of the blend. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1235-1245, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 30
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; oligomer ; poly(ethylene glycol) ; epoxy resin ; concentrated solution ; crystallinity ; thermoreversible gel ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(ethylene terephthalate) (PET) was rapidly crystallized through thermoreversible gelation in a liquid ethylene glycol oligomer or in epoxy resin. The solutions formed gel rapidly on cooling. Polarized light microscopy and small-angle light scattering showed that these gels contain large, regular PET spherulites. The gels may be formed by two consecutive processes: the phase separation and crystallization, and gelation by formation of a three-dimensional PET network in the oligomer solvents, where the nodes of the network are PET spherulites. The crystallinity of PET recovered from polymer/oligomer gels is near 72% measured by wide-angle X-ray diffraction method, which is about 20% higher than PET samples crystallized by solution crystallization in small molecule solvent, high temperature annealing, and stretching techniques. It takes only a few minutes to form the highly crystalline phase PET in the PET/oligomer system, and the crystallinity of the dried gel is independent of the concentration of the original solution. Excimer-fluoresence and Raman spectroscopic studies indicated that PET recovered from the gels are in an ordered state with few chain entanglements. The entanglement density of the recovered PET recovered from a 20 wt % solution in ethylene glycol oligomer is as low as that of freeze-extracted PET from a 0.5 wt % solution in phenol. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1219-1225, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 31
    ISSN: 0887-6266
    Keywords: PET fiber ; continuous zone-drawing/zone-annealing ; high-modulus ; mechanical properties ; microstructure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A continuous zone-drawing/zone-annealing method was applied to poly(ethylene terephthalate) fibers in order to improve their mechanical properties. Apparatus used for this treatment was assembled in our laboratory. The continuous zone-drawing treatment was carried out at a drawing temperature of 103°C under an applied tension of 6.6 MPa to fully orient amorphous chains in the drawing direction without inducing thermal crystallization. The continuous zone-annealing treatment was carried out twice at an annealing temperature of 160°C under 102.2 MPa and at 183°C under 161.1 MPa to crystallize the highly oriented amorphous chains. The fiber was continuously drawn and annealed at a rate of 420 mm/min. The fiber obtained had a birefringence of 0.260, a degree of crystallinity of 55%, a tensile modulus of 18 GPa, and a storage modulus of 21 GPa at 25°C. Despite the large difference in the treating speed between the continuous zone-annealing and zone-annealing, their values are approximately equal to those of the zone-annealed PET fiber that was reported previously. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 473-481, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: crystallization ; DSC ; multiple melting ; nascent morphology ; polyethylene ; synchrotron ; UHMW PE ; WAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nascent morphology of UHMW PE exhibits high melting point, high crystallinity, and increased WAXS line breadth relative to samples formed by melt crystallization. Different empirical relationships between crystal size and melting point are observed for nascent and molded samples. This differentiation is removed following nitric acid treatment of the nascent flake. Solid-state annealing behavior is differentiated by several regimes. Regime I is characterized by increasing crystallite dimensions and crystallinity at low annealing temperatures. Regime II[a] and II[b] is identified by double melting in DSC scans of moldings and nascent flake, respectively. The double melting is due to partial melting with incomplete recrystallization. Regime II[a] of moldings is differentiated from Regime II[b] of flake by an increase in melting point of the higher melting endotherm. Within Regime II[b], the partial melting of the nascent structure is sensitive to the distribution of morphological stability. Regime III is initiated at annealing temperatures approaching the zero heating rate melting point, and shows melting kinetics by DSC or time-resolved WAXS using synchrotron x-ray radiation. The superheat, partially associated with Regime III behavior, is sensitive to morphological heterogeneity and annealing history. Morphological models are discussed which highlight the role of noncrystalline regions and melting kinetics on the melting behavior of nascent form crystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 495-517, 1998
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: PMMA ; ion beam ; scission ; G value ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chemical and physical effects induced by bombardment of nearly monodisperse Poly(methyl methacrylate) (PMMA) with energetic ions (He+) at 200 keV have been studied. Bond scission is the main results of low fluence ion irradiation but, at high fluence there is a regime transition of PMMA from positive tone resist behavior to negative tone. The ion-induced chemical reactions in the macromolecular film give rise to gas evolution and chemical changes in the solid residue. The gas formed during the bombardment has been studied by means of a mass spectrometer, while the solid polymer has been characterized by measuring the molecular weight distribution (MWD) and the absorption coefficient in the Near Infrared (NIR), visible, and ultraviolet regions. X-ray Photoelectron Spectroscopy (XPS) has been performed to learn what happens at the surface of the polymer after bombardment. The main result of these studies is that at fluence higher than 1013 cm-2 both chemical and physical effects follow a nonlinear behavior due to the transition from a single-track regime to a track overlap regime. This transition is explained in terms of progressive chemical change of the irradiated polymer from the pristine chemical structure to a new one depleted of the ester pendent groups. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 655-664, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 0887-6266
    Keywords: impedance spectroscopy ; chemical and physical changes ; glass formers ; reactive polymers ; in situ monitoring ; dielectric properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study was conducted aimed at establishing the nature of chemical and physical phenomena in polymeric and nonpolymeric glass formers that can be observed by impedance measurements. Various systems were investigated that undergo a temporal evolution of structure as a result of chemical reactions and physical processes such as crystallization, vitrification, or phase separation. Distinct and systematic changes in impedance during crystallization and vitrification confirmed that these events could be monitored by impedance spectroscopy. Of particular interest was the potential use of impedance measurements in detecting gelation in crosslinking polymers. It was shown that the experimentally observed “knee” in imaginary impedance during reaction shifts with frequency and, hence, cannot be used to measure gelation. But a new insight at the molecular level was obtained by employing a novel experimental approach based on simultaneous dielectric-infrared measurements. Evidence was generated to support the formation of a hydrogen-bonded complex in the vicinity of gel point in polymer networks, which affords a vehicle for the migration of intrinsic charges and provides a contribution to the overall conductivity. This finding should be explored further because it suggests the possibility of correlating dielectric response with gelation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 641-653, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 0887-6266
    Keywords: polyacrylamides ; specific viscosity ; polyelectrolyte solutions ; light scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependences of the specific viscosity of several polyelectrolytes on polyelectrolyte concentration, salt concentration or solution ionic strength, solution pH value, solvent quality, and solution temperature were systematically investigated. We found that the specific viscosity obeys a more general relation: ηsp = Acp2/(cp + 2cs)3/2 + B, where ηsp is the polyelectrolyte specific viscosity, cp and cs are polymer and salt concentrations, respectively. The prefactor A depends critically on chain size, solvent quality, and temperature in qualitative agreement with the theory proposed by Rabin et al. The intercept B is nonzero or less than zero in polyelectrolyte solutions with low ionic strength. When a sufficient amount of salt has been added, B is reduced to zero and we recover the Rabin et al.'s relation. The physical interpretation for the intercept B is that it represents the inverse of the strength of electrostatic interaction between a polyion and counterions, in quantitative agreement with the well-known emperical Fuoss's relation. Furthermore, the existence of nonzero B allows us to calculate the condition for the maximum in the reduced viscosity-polymer concentration curve in a polyelectrolyte solution system without salt. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 743-753, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 0887-6266
    Keywords: positron annihilation lifetime spectroscopy ; free volume ; transition temperatures ; poly(silylenemethylene)s ; dynamic mechanical analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Amorphous and crystalline poly(silylenemethylene)s with the repeating PhRSiCH2 (R : Me or Ph) units were characterized by positron annihilation lifetime spectroscopy (PALS) to gain insights into the molecular motions of these polymers. The temperature dependence of the ortho-positronium lifetime (τ3) and intensity (I3) was examined from 50 to 470 K for each sample. The glass transition temperature of each polymer was easily distinguished by a change in the slope of τ3 spectrum. Both polymers exhibited a steep drop of I3 at 130-140 K being probably assignable to the transition arising from the motions of phenyl groups, which was almost undetectable by means of differential scanning calorimetry or dynamic mechanical analysis. Several other transitions of these polymers detected by PALS are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 755-761, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: poly(aryl ether ketone)s ; dielectric relaxation spectroscopy ; dynamic mechanical analysis ; α-relaxation ; β-relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relaxation behavior of four amorphous poly(aryl ether ketone)s was investigated using dielectric relaxation spectroscopy and dynamic mechanical analysis. The temperature dependence of the relaxation times of the glass transition process and the cooperative nature of this process were unaffected by changes in polymer structure. The temperature location of the loss peaks for all polymers progressed smoothly between the low frequency of the mechanical measurements and the higher frequencies of the dielectric probe. Differences were observed in mechanical activation energy and dielectric relaxation strength for one polymer which contained a significant concentration of meta linkages, compared with the para-linked polymers, while relaxation broadness was generally greater in the dynamic mechanical mode. Changes in chemical structure had little effect on the shape, intensity, and location of the β-relaxation peak, the main observation being that the Arrhenius activation energy measured by dynamic mechanical analysis was significantly higher than that calculated from the dielectric data. The dielectric β-relaxation was sensitive to absorbed moisture. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 851-859, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 38
    ISSN: 0887-6266
    Keywords: small-angle neutron scattering ; SANS ; polystyrene ; polyvinylmethylether ; radius of gyration ; Zimm analysis ; random phase approximation ; phase diagram ; polymer blends ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle neutron scattering was used to measure the radius of gyration and thermodynamics of blends of poly(vinylmethylether) (PVME) at dilute concentration in deuterated polystyrene (PSD). The data were analyzed using the Zimm equation and the random phase approximation theory. For PVME with a weight-average molecular weight of 38,400 the value of the radius of gyration, Rg, was found to be 47 Å in the limit of the concentration of PVME extrapolated to zero. Analysis of the temperature dependence of the Flory interaction parameter, χ/v0, indicates that phase separation should occur at approximately 300°C for a sample with φPVME ≅ 9%. No significant temperature dependence of Rg was found over the experimental range studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1-9, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 39
    ISSN: 0887-6266
    Keywords: liquid crystals ; thermosets ; smectic epoxy ; nematic ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Deformation experiments were carried out for densely crosslinked smectic-like networks obtained from diepoxy monomers with twin mesogen architecture. For the initially unoriented smectic networks, the network could be aligned up to an orientation parameter of 0.35 by applying 8 MPa of external stress in the rubbery regime. X-ray diffraction measurements revealed that the deformed smectic network possesses both smectic-A like and smectic-C like structure. It is thought that after extension domains initially oriented parallel to the external stress displayed a smectic-A-like structure, whereas domains initially tilted with respect to the tensile direction showed a stress-induced smectic-C like structure. A smectic network oriented under a.c. electric fields with an orientation parameter of 0.4 had a smectic-A like structure and possessed linear elasticity in the rubbery regime. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 31-38, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 40
    ISSN: 0887-6266
    Keywords: fluorescence emission technique ; dynamic light scattering ; reduced viscosity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, rheological, and fluorescence properties of a cationic water-soluble copolymer, naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer), poly(DSQADMAPM)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the cationic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. The salt and pH responsiveness inherent to the cationic copolymer systems is a function of ionic group type. Experimental results indicate that IE/IM increases steadily with increases in polymer concentration and IE/IM values for a given polymer concentration are higher in salt. At low pH values, IE/IM is high and excimer emission increases as the quaternary amino groups (R4N+) are screened out. Dynamic light scattering (QELS) measurements indicate that diffusion coefficients of the cationic copolymer increase and the hydrodynamic diameters decrease with increasing salt concentration. Viscosity studies reveal that the polymer coil shrinks as salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of thallium (Tl+) with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty in reacting with bound naphthalenes located in the shrunk polymer coil. The cationic copolymer is depicted as an expanded polymer coil in deionized water because of intra- and interchain repulsions. Consequently, salt addition breaks down the repulsions and enhances intrapolymer micellization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 11-19, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 41
    ISSN: 0887-6266
    Keywords: liquid crystal ; block copolymer ; polyester block ; polymethacrylate block ; magnetic field ; X-ray diffraction ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase and orientational behaviors of a series of liquid crystalline (LC) AB-type diblock copolymers comprising thermotropic main-chain (MC) polyester and side-group (SG) polymethacrylate blocks were investigated by X-ray diffraction. The MC and SG blocks were phase separated and gave rise to their individual mesophases that coexisted at equilibrium. The samples were oriented by using either a magnetic field or a mechanical field. In magnetically aligned samples both the MC and SG microphases were oriented with their smectic planes orthogonal to the magnetic field direction, independent of the copolymer composition. Mechanically aligned, fiber samples showed different orientations of the MC and SG smectic planes for different sample compositions. In this case the disposition of the smectic planes of the MC and SG blocks was driven by the relative length of the two blocks. Some features of the X-ray patterns of the copolymers were compared to those of the MC and SG homopolymers. In addition, the MC smectic domains crystallized on annealing without affecting the orientation that had been achieved by applying a magnetic field. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 21-29, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 42
    ISSN: 0887-6266
    Keywords: poly-p-phenylenebenzobisoxazole ; X-ray scattering ; transmission electron microscopy ; Young's modulus ; tenacity ; crystal size ; orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies. Crystal size, orientation of the crystal, fibrils, microvoids, and fine structure were discussed. It was found that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal (160 Å) and the transverse (110 Å) directions. Crystal modulus estimated by extrapolation to perfect orientation on the plot of the fiber modulus as a function of fiber orientation (Northolt's method) shows discrepancy from the crystal modulus directly obtained by X-ray scattering. This discrepancy means that the Northolt's model is insufficient to describe the Young's modulus of PBO fiber. Microvoids elongated to the fiber direction were examined by small-angle X-ray scattering and transmission electron microscopic methods. The diameter of the microvoids was 20 Å to 30 Å and the fiber had a very thin microvoids-free layer (0.2 μm). Preferential orientation of the a-axis of crystal in the fiber was also confirmed. Summarizing these results, a structure model of the PBO fiber was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 39-48, 1998
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 0887-6266
    Keywords: PDLC ; polarization ; angular discrimination ; copolymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electrooptic responses (voltage and angular-dependent transmittance) of polymer/liquid crystal composite films with H, V, and unpolarized lights have been studied based on a nematic liquid crystal (Ro-5921) and four types of homopolymers and copolymers from ethyl methacrylate and styrene with different compositions. In this way, the index ratio of the polymer (np) to the ordinary refractive index of liquid crystal (no)(np/no) has been varied systematically, and the effect of the index ratio on viewing angle, applied voltage, response times, and transient response have been investigated. With increasing styrene content in the copolymer, droplet size increased, threshold (Vth) and saturation (Vsat) voltage, and rise time decreased. With np ≲ no, maximum transmittance occurred at normal incidence, regardless of the type of polarization. On the contrary with np 〉 no, V-polarization gave a peak in the transmittance-voltage curve, and transmittance overshot upon removal of the field, and these were interpreted in terms of effective refractive index and two-step relaxations. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 55-64, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 44
    ISSN: 0887-6266
    Keywords: substituted poly(paraphenylene) ; phase transitions ; synchrotron radiation ; mesophases ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal behavior of poly(para-2,5-didecyl-p-phenylene) has been investigated by differential scanning calorimetry and real time X-ray diffraction. Poly(para-2,5-didecyl-p-phenylene) is a semicrystalline material that crystallizes in a layered structure. The system exhibits two thermal transitions in the investigated temperature range. The first one, occurring at lower temperatures, provokes a reduction of the layered spacing accompanied by an appreciable disordering of the lateral side chains. Above the first transition the material is shearable, highly viscous, and birefringent. Thus, we have associated this transition to the formation of a layered mesophase. The higher temperature transition exhibits a twofold endothermic DSC peak and is characterized by the disappearance of X-ray diffracted intensity. At temperatures above the second transition the system presents the characteristics of an isotropic melt. Consequently, we have associated this transition with the complete disordering of the polymeric backbones. By following an appropriate thermal treatment it has been shown that the twofold shape of the endotherm characterizing the higher temperature transition can be changed into a single endotherm. This effect has been interpreted as being due to the kinetics of main-chain ordering. This ordering seems to proceed by the initial growth of domains with a high level of order followed by the subsequent increase of these domains through the inclusion of less ordered material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 49-54, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 45
    ISSN: 0887-6266
    Keywords: polybutadiene ; poly(methyl methacrylate) ; poly(butadiene-block-methyl methacrylate) ; compatibilization ; micelle ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 85-93, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 46
    ISSN: 0887-6266
    Keywords: poly(ether ether ketone) (PEEK) ; poly(ether ketone ketone) (PEKK) ; solvent-induced crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relationship between semicrystalline morphology and glass transition temperature has been investigated for solvent-crystallized poly(ether ether ketone) (PEEK) and poly(ether ketone ketone) (PEKK). Solvent-crystallized specimens of both PEEK and PEKK displayed a sizeable positive offset in Tg compared to quenched amorphous specimens as well as thermally crystallized specimens of comparable bulk crystallinity; the offset in Tg for the crystallized samples reflected the degree of constraint imposed on the amorphous segments by the crystallites. Small-angle X-ray scattering studies revealed markedly smaller crystal long periods (d) for the solvent-crystallized specimens compared to samples prepared by direct cold crystallization. The strong inverse correlation observed between Tg and interlamellar amorphous thickness (lA) based on a simple two-phase model was in excellent agreement with data reported previously for PEEK, and indicated the existence of a unique relationship between glass transition temperature and morphology in these poly(aryl ether ketones) over a wider range of sample preparation history and lamellar structure than was previously reported. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 65-73, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 47
    ISSN: 0887-6266
    Keywords: blends ; melting behavior ; miscibility ; FTIR ; hydrogen bond interactions ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(ε-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature (Tg), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the Tg of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymer-polymer interaction parameter, χ32, was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of χ32 obtained for HSMS/PCL blends has been compared with the value of χ32 for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 95-104, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 48
    ISSN: 0887-6266
    Keywords: ester interchange reaction ; Monte Carlo method ; copolymerization ; degree of randomness ; miscible polyester blend ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of reaction variables on the degree of randomness in copolymers formed by ester interchange reaction in miscible polyester melt blends were systematically investigated using a Monte Carlo method. Three reaction variables such as the molecular weight difference between two component polymers, the blend ratio, and the reaction ratio of end attack to bond flip, were particularly considered on the cubic lattice model. Ester interchange reactions were assumed to take place during reptational chain motions. It was found that the copolymerization was dependent upon the molecular weight difference and reaction ratio: As the molecular weight difference becomes smaller and when both end attack and bond flip reactions are involved simultaneously, the copolymerization is accelerated. However, the blend ratio does not affect the copolymerization process. This result is discussed in relation to the polymer chain conformation for the ester interchange reaction. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1637-1645, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 49
    ISSN: 0887-6266
    Keywords: microstructure ; properties ; poly(1,3-cyclohexadiene) ; living anionic polymerization ; hydrogenated derivatives ; triblock copolymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relationship between the microstructure and the properties of poly(1,3-cyclohexadiene)s, obtained by living anionic polymerization with an alkyllithium/amine system, and their hydrogenated derivatives are reported. The 1,2-bond/1,4-bond molar ratio of poly(1,3-cyclohexadiene) was determined by measuring 2D-NMR with the H—H COSY method. The glass transition temperature of poly(1,3-cyclohexadiene) was found to rise with an increase in the ratio of 1,2-bonds to 1,4-bonds or with an increase of the number average molecular weight. The 1,2-bond of the polymer chain gives a high flexural strength and heat distortion temperature. Hydrogenated poly(1,3-cyclohexadiene) has the highest Tg (231°C) among all hydrocarbon polymers ever reported. 1,3-Cyclohexadiene-butadiene-1,3-cyclohexadiene triblock copolymer and 1,3-cyclohexadiene-styrene-1,3-cyclohexadiene triblock copolymer have high heat resistance and high mechanical strength. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1657-1668, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 50
    ISSN: 0887-6266
    Keywords: sorption ; dilation ; diffusion ; conditioning effect ; glassy polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sorption, dilation, and diffusion behaviors were studied for the system of polysulfone/CO2 with regard to the effects of CO2 conditioning, i.e., exposure to high-pressure CO2. Concurrent measurements of solubility, dilation, and diffusivity were performed for polysulfone films before and after the conditioning at 25 and 50 atm. While the solubility and dilation were enhanced by the conditioning, the diffusivity appeared to be depressed. Results were analyzed on the basis of the dual-mode sorption model, with the assumption that the Henry's law dissolution was not affected by the conditioning. Consistent description was achieved then by attributing the changes to increased amount of Langmuir adsorption. The conditioning effect on the diffusivity, which had not been reported before based on CO2 sorption kinetics, suggests that the permeability of glassy polymers would not always be enhanced by the conditioning, but may also be decreased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1695-1702, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 51
    ISSN: 0887-6266
    Keywords: crystallization kinetics ; thermotropic liquid crystalline polymers ; polyimide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied the nonisothermal and isothermal crystallization kinetics of an aromatic thermotropic liquid crystalline polyimide synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 1,3-bis[4-(4′-aminophenoxy) cumyl] benzene (BACB) by means of differential scanning calorimetry (DSC). Polarized light microscopy (PLM) and wide-angle X-ray diffraction (WAXD) results confirm that this polyimide exhibits a smectic texture. Nonisothermal crystallization showed two strong and one weak exothermic peaks during cooling. The phase transition from isotropic melt to liquid crystalline state is extremely fast which completes in several seconds. The mesophase transition has a small Avrami parameter, n, of approximate 1. The isothermal crystallization of 253-258°C has been examined. The average value n is about 2.6 and the temperature-dependent rate constant k changes about two orders of magnitude in the crystallization temperature range of 6°C. The slope of ln k versus 1/(TcΔT) is calculated to be -2.4 × 105, which suggests nucleation control, via primary and/or secondary nucleation for the crystallization process. During the annealing process, a new phase (slow transition) is induced, which grows gradually with annealing time. At lower annealing temperatures (220-230°C), the slow transition process seems not to be influenced by the crystals formed during cooling process and its Avrami parameter n is ca. 0.3-0.4. However, the slow transition was hindered by the crystals formed during cooling process when annealed at higher temperature (230-240°C). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1679-1694, 1998
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 52
    ISSN: 0887-6266
    Keywords: complex shear modulus ; ultrasonic measurements ; dynamic-mechanical measurements ; acrylic-type copolymers ; film formation ; glass-rubber relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An ultrasonic shear wave reflection method was applied to study film formation and temperature dependence of the complex shear modulus (G*=G′ + iG″) in different amorphous films made of aqueous dispersions of acrylic-type copolymers. The data are compared with dynamic-mechanical measurements in the low frequency range. It is shown that the temperature dependence of the storage (G′) and the loss modulus (G″) for both methods can be fitted by the same set of parameters using the Havriliak-Negami function incorporating the Vogel-Fulcher-Tamman-Hesse equation for the temperature dependence of relaxation times. The temperature dependence of the relaxation times obtained from the fits to the ultrasonic shear modulus is compared to the shift factors of the dynamic-mechanical measurements. The agreement between both methods is good. This suggests an almost thermorheological simplicity of the samples for the main glass-rubber relaxation and demonstrates the capacity of the ultrasonic rheometer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1703-1711, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 53
    ISSN: 0887-6266
    Keywords: photo-assisted poling ; polymer dynamics ; polymer structure ; nonlinear optical polyimides ; high glass transition temperature ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have used combinations of light, heat, and electrostatic fields to investigate the orientation of nonlinear azo-chromophores chemically incorporated into high glass transition temperature (Tg) polyimides. A number of nonlinear optical polyimides have been synthesized in which the interaction between the nonlinear optical chromophore and the polymer main chain was systematically altered to determine to what extent this steric interaction influences the orientation of the nonlinear chromophore. Chromophores in polymers may be oriented by a number of methods: (a) polarized light at room temperature (i.e., photo-induced orientation or PIO), (b) polarized light and electric fields (i.e., photo-assisted poling or PAP) at temperatures ranging from room temperature to the polymer Tg, and (c) electric fields at Tg (thermal poling). While thermal poling and PIO are usually possible, PAP depends strongly on the molecular structure of the polymer. Previously we have shown that PIO can be accomplished at room temperature in a system where the nonlinear chromophore is embedded into the polyimide main chain via the donor substituent, and this orientation can only be thermally erased at temperatures approaching Tg. In this article we show that, whereas photoisomerization can efficiently depole donor-embedded polyimides in a matter of few minutes at room temperature, PAP does not induce any polar order. This behavior is in marked contrast to a structurally related, side-chain, nonlinear polyimide, in which the azo chromophore is tethered via a flexible linkage to the polymer backbone. In this case some PAP occurs even at room temperature, while no PAP is observed for a donor-embedded system with a similar Tg. We suggest that the orientation during PAP below Tg in the side-chain polyimide is primarily due to the movement of the azo side chains, and there is a very little coupling of this motion to the main chain. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1669-1677, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 54
    ISSN: 0887-6266
    Keywords: polymer ; diffusion ; free-volume theory ; inverse gas chromatography ; gravimetric sorption ; ethylene-propylene-diene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Self-diffusion and partition coefficients were measured for two commercial ethylene-propylene-diene copolymers (EPDM) and five solvents at infinite dilution using inverse gas chromatography. Mutual diffusion coefficients for solvents in EPDM also were measured for finite concentration using gravimetric sorption for three of the solvents. From the inverse gas chromatography experimental values for self-diffusion coefficients were obtained. Free-volume parameters were obtained through regression of the self-diffusion coefficient as a function of temperature. Mutual diffusion coefficients as a function of concentration were predicted using free volume theory and compared with experimental data obtained using gravimetric sorption. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1713-1719, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: phenolic ; miscibility ; hydrogen bonding ; PEO ; PEG ; PVA ; glass transition temperature ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The specific interaction strength of novolak-type phenolic resin blended with three similar polymers [i.e., poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), and poly(vinyl alcohol) (PVA)] were characterized by means of glass transition temperature behavior and Fourier transform infrared (FTIR) spectroscopy. The interassociation formed within phenolic blends with the addition of a modifier not only overcomes the effect of self-association of the phenolic upon blending, but also increases the strength of phenolic blend. The strength of interassociation within the phenolic blend is the function of the hydrogen bonding group of a modifier, in increasing order, is phenolic/PVA, phenolic/PEG, and phenolic/PEO blend, corresponding to the result of “q” value in the Kwei equation. The FTIR result is in agreement with the inference of Tg behavior. In addition, the fact that the specific strength of hydrogen bonding of hydroxyl-hydroxyl is stronger than that of hydroxyl-ether can also be concluded. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1721-1729, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 56
    ISSN: 0887-6266
    Keywords: poly(p-phenylene sulfide) fiber ; zone-drawing ; zone-annealing ; mechanical properties ; DSC thermogram ;