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  • Polymer and Materials Science  (4,055)
  • 1990-1994  (4,055)
  • 1970-1974
  • 1993  (4,055)
Collection
Publisher
Years
  • 1990-1994  (4,055)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: biodegradable polymers ; polyanhydride ; dimer fatty acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of aliphatic copolyanhydrides was synthesized from nonlinear hydrophobic dimers (FAD) of erucic acid and sebacic acid which possessed the desired physico-chemical and mechanical properties for use as a carrier for drugs. The polymers were synthesized by melt condensation to yield film-forming polymers with molecular weights of 250,000. The copolymer composition was determined by 1H-NMR and gravimetric methods. In vitro degradation studies showed that these polymers degrade following a first-order kinetics with a rapid degradation in the first 10 days leaving a residue which is mostly the FAD comonomer. The drug release from the polymer also followed a first-order kinetics which correlates with the degradation process of the polymer. Drugs like carboplatin, methotrexate, tetracycline, and gentamicin were released in vitro for over 2 weeks and in some cases over 6 weeks. In vivo biocompatibility tests in rats and rabbits in the brain, muscle, and subcutaneously, demonstrated their toxicological inertness and biodegradability. The 1 : 1 copolymer of FAD : SA was selected as a carrier for various applications including a gentamicin-releasing implant which is now undergoing human clinical trials for the treatment of osteomyelitis. © 1993 John Wiley & Sons, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: photopolymerization, dye-sensitized ; radical polymerization ; photochemistry of dyes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Styrene can be photopolymerized with methanolic solutions of safranine T(STH+) in the absence of any additives. Under these conditions the monomer acts as an electron donor for the excited singlet state of STH+, and after electron transfer an initiating semireduced STH+ radical is produced. The experimentally determined monomer exponent of α = 2 indicates additional deactivation reactions of the primary radicals. The polymerization rate depends on the dye concentration also in those regions, in which all light is already absorbed. Presumably, this dependence is caused by a comproportionation reaction between STH+ and substituted leuco-safranine T formed in the course of polymerization. © 1993 John Wiley & Sons, Inc.
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  • 3
    ISSN: 0887-624X
    Keywords: aromatic polyamides ; pendent groups ; 5-phenylsulfonylisophthalic acid ; polycondensation ; NMR, solubility ; water uptake ; mechanical strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of polyisophthalamides containing phenylsulfonyl groups was prepared from seven aromatic diamines and 5-phenylsulfonylisophthalic acid by the phosphorylation condensation method, and from 5-phenylsulfonylisophthaloyl chloride by the solution polycondensation method at low temperature. When compared to the analogous unmodified polyisophthalamides, the modified ones were found to be essentially amorphous, and they showed better solubility in organic solvents, and slightly higher glass transition temperatures. Thermogravimetric analysis showed that the polyisophthalamides containing pendent phenylsulfonyl groups have thermal stabilities similar to the unmodified ones. Mechanical strength of films and water sorption were also investigated. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 0887-624X
    Keywords: tetrafluorobenzene derivatives ; fluorinated polymers ; condensation polymers ; polyesters ; polycarbonates ; polyurethanes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel diol monomer, α,α,α′,α′-tetramethyl-1,4-tetrafluorobenzenedimethanol, has been synthesized by a convenient route which involves the addition of acetone to 1,4-dilithiotetrafluorobenzene and can be purified by washing with hexanes. It does not directly undergo condensation polymerizations with diacid chlorides. Its disodium salt, prepared by its reaction with sodium hydride, similarly fails to undergo such polymerizations readily. However, the dilithium salt, prepared in situ by the reaction of the title diol with 2 equiv of n-butyllithium in tetrahydrofuran, is suitable for the preparation of various classes of condensation polymers. Four polyesters and one polycarbonate derived from the reactions of the dilithium salt of the diol with adipoly dichloride, sebacoyl dichloride, isophthaloyl dichloride, terephthaloyl dichloride, and phosgene and two polyurethanes derived from its reactions with tolylene-2,4-diisocyanate and methylene-di-1,4-phenyl diisocyanate were prepared. Each was fully characterized by GPC, NMR, IR, and UV-visible spectroscopies, and the results of these studies are reported herein. © 1993 John Wiley & Sons, Inc.
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  • 5
    ISSN: 0887-624X
    Keywords: polymerization, gel-free ; MBA ; PDP-MSA ; TGA ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gel-free cyclopolymerization of N,N′-methylenebisacrylamide has been carried out using potassium peroxodiphosphate (PDP) as initiator in combination with different activators such as mercaptosuccinic acid (MSA) and thioglycollic acid (TGA) in an inert atmosphere at 45 ± 1°C and 40 ± 1°C, respectively. The rate of polymerization was found proportional to the first power of the monomer and activator concentration and the half-power of PDP in both redox systems. A mechanism involving cyclopolymerization in the propagation path has been proposed. © 1993 John Wiley & Sons, Inc.
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  • 6
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 0887-624X
    Keywords: chemical amplification ; photoresist ; poly(p-hydroxystyrene) ; photocrosslinking ; carbocationic ; radiation-sensitive ; crosslinker ; triarylsulfonium salt ; thin-film chemistry ; UV ; E-beam ; x-ray ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New resist systems based on acid-catalyzed, electrophilic aromatic substitution are described. These new resists show high sensitivity to deep UV and E-beam radiation with values approaching 2 mJ/cm2 and 2 μC/cm2, respectively. The resists are based on a three component system consisting of poly(4-hydroxystyrene), a polyfunctional, low molecular weight, latent electrophile, and a photoactive onium salt used as an acid generator. Irradiation of the resist film produces a latent image of acid dispersed in the matrix. During the postbaking step the photo-generated acid reacts with the latent polyfunctional electrophile and releases a reactive carbocationic intermediate with concomitant liberation of acetic acid. The carbocationic intermediate then reacts with neighboring phenolic moieties in a crosslinking reaction. The substitution reaction liberates a proton, making the process catalytic in nature, thus incorporating the concept of chemical amplification. These highly sensitive materials can be used as nonswelling negative multipurpose resists that function in deep-UV, x-ray or E-beam modes. © 1993 John Wiley & Sons, Inc.
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  • 8
    ISSN: 0887-624X
    Keywords: free radical polymerization ; dimethylphenyl methacrylates ; kinetics ; dilatometry ; dipoles interaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of free radical polymerization of all six existing isomeric dimethylphenyl methacrylates were studied in bulk at 60°C, initiated by dilauroyl peroxide, using dilatometry. The different polymerization rates observed, resulting from the different monomer structures, are discussed in terms of steric and other effects, considering also the previous results for tolyl methacrylates. © 1993 John Wiley & Sons, Inc.
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  • 9
    ISSN: 0887-624X
    Keywords: solvent effect ; multi-armed monomer ; polycascade polymer ; hydrogen bond interaction ; radical polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerization of vinyl biphenyl derivatives containing a pendant oligo(oxyethylene)cyclotriphosphazene (VBMEP, —(OCH2CH2)nOCH3, n = 1; VBDEP, n = 2; VBTEP, n = 3) was carried out in various solvents. The conversions of these monomers increased with increasing β values, solvent hydrogen bond acceptor abilities, indicating that the hydrogen bond formation is the most important factor in the polymerization. 13CNMR study showed that the reactivity of the monomer is influenced by the hydrogen bond interaction. In ethanol, the kinetic orders of monomer and initiator concentrations for the polymerization of VBDEP were different from those in 1,2-dichloroethane (DCE), which suggest the predominant occurrence of primary radical termination. The intrinsic viscosity of poly(VBDEP) with M̄n = 22 000 in DCE was two times higher than that in ethanol, and plots of intrinsic viscosity versus conversion of VBDEP gave a straight line. The results suggest that the polymer chains in ethanol are in a coiled conformation, whereas in DCE they are in a relatively extended structure, and that the propagation is affected by the conformational change. These behaviors originated from the hydrogen bond formation between polymers and solvents are discussed. The copolymerization of styrene with multiarmed monomers and the properties of polycascade polymers obtained are also described. © 1993 John Wiley & Sons, Inc.
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  • 10
    ISSN: 0887-624X
    Keywords: poly(vinyl chloride) ; thermal degradation ; mathematical models ; length of dehydrochlorination chain ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dehydrochlorination of different samples of PVC under vacuum with continuous removal of HCl by freezing, has been studied at 180-210°C. The comparison of the kinetic curves of the dehydrochlorination of various samples of PVC which were obtained by us and other investigators, with the theoretical curves for the thermal degradation of idealized PVC in the absence of HCl has been carried out. This had made it possible to evaluate the influence of unstable fragments present in the original polymer on the initial rate of PVC degradation quantitatively. It has been shown that the distinction between the stationary rates of the dehydrochlorination of various samples of PVC is determined by the difference of the values of the average length of dehydrochlorination chain, lav. The most probable interval of the values of lav has been ascertained to be 4-12. It is established that the most probable value of the constant of the rate of dehydrochlorination of normal links of PVC, k0, is 2.1 × 10-7-2.5 × 10-7 s-1 at 200°C. © 1993 John Wiley & Sons, Inc.
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  • 11
    ISSN: 0887-624X
    Keywords: polyimides ; photooxidation ; surface modification ; gas separations ; ultraviolet irradiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyimide membranes that contain both the phthalimide chromophore and abstractable hydrogens undergo photochemically-induced oxidative surface modification when they are irradiated with ultraviolet (UV) light for 0.5-30 min in air. The reaction requires 200-300 nm light and the presence of oxygen, and the surface-modified membranes show much higher oxygen/nitrogen selectivities than the untreated films. A mechanism for the photochemical reaction that is based on the photochemistry of structurally-similar monomeric phthalimides is proposed. The observed selectivity increases can also be explained by this mechanism. © 1993 John Wiley & Sons, Inc.
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  • 12
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; isotachophoresis ; oligomer ; free radical ; aqueous phase ; styrene ; termination ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concentrations and probable nature of charged oligomers formed by aqueous-phase termination in the persulfate-initiated emulsion polymerization of styrene were measured by isotachophoresis. Isotachophoresis has some advantages over other techniques (e.g., GPC, UV spectroscopy) in that it separates species according to their molecular weight, geometry, and charge. The charged water-soluble oligomeric species were detected in experiments in which particles were nucleated in a surfactant-free environment. Identification of the moieties present was made by comparison with model compounds. Evidence was found for bimolecular combination as a major mechanism of termination in the aqueous phase, although the possibility of disproportionation could not be ruled out. The species formed in the aqueous phase under saturated monomer conditions were found to be subject to further reaction towards the end of polymerization. The surface adsorption characteristics of the compounds formed were compared with those of known surfactants and showed good agreement with the assumptions in the model of Maxwell et. al. [Macromolecules, 24, 1629 (1991)] for initiator efficiencies in emulsion polymerization. The relatively large concentrations of nonradical aqueous-soluble oligomeric compounds demonstrate conclusively that initiator efficiencies are not 100%, as is often assumed in such systems. © 1993 John Wiley & Sons, Inc.
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  • 13
    ISSN: 0887-624X
    Keywords: β-chitin ; squid pens ; deacetylation ; crystallinity ; hygroscopicity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Chitin was isolated from squid pens, and the characteristic chemical and physical properties were elucidated in comparison with those of shrimp chitin, α-chitin. Deacetylation behavior of the squid chitin was first studied to look into the reactivity of β-chitin and also to establish an efficient procedure for preparing squid chitosan. The squid chitin proved to show much higher reactivity in alkaline deacetylation than shrimp chitin. Although it was deacetylated quite easily, the product assumed a dark brown color under the ordinary reaction conditions for shrimp chitosan. Squid chitosan was successfully prepared by repeated alkaline treatments under mild conditions, particularly with high concentration alkali at low temperatures, without appreciable discoloration. The structural characteristics of the squid chitin were discussed on the basis of the IR and x-ray analysis data. The crystalline structure of squid chitin was destroyed easily on deacetylation compared to that of shrimp chitin, and moreover, the resulting squid chitosan was amorphous unlike crystalline shrimp chitosan. The squid chitin was characterized by the remarkable affinity for organic solvents and water. Squid chitin and chitosan also showed much higher hygroscopicity and retention of the absorbed water than shrimp chitin and chitosan and are considered to be useful as highly hydrophilic materials. © 1993 John Wiley & Sons, Inc.
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  • 14
    ISSN: 0887-624X
    Keywords: calixarene ; anthracene ; photodevice ; optical data storage ; host-guest interaction ; PVC membrane ; plasticizer effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 15
    ISSN: 0887-624X
    Keywords: alkyl substituted phenol ; aliphaticamine ; para-formaldehyde ; Mannich reaction ; NMR characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The study of the reactions which take place when α-methyl-ω-phenolpolyisobutylene is polycondensed with triethylenetetramine (TETA) and para-formaldehyde (Mannich condensation) is carried out on model systems including monofunctional [2,4-di-tert-butylphenol (A), dibutylamine (B), and dodecylamine (B′)] and difunctional reactants [4-tert-butylphenol (A′) and 1,6-hexamethylenediamine (B″)]. With the exception of the A + B system which gives only Mannich condensation, all the systems including at least one difunctional reactant are characterized by side reactions which accompany the Mannich condensation. However, when one of the compounds is monofunctional (A + B;′ A′ + B′) only nonpolymeric molecules are formed; their structures were determined by 1H- and 13C-NMR spectroscopy. On the other hand, when both reactants are bifunctional (A′ + B; A′ + TETA) polymers are formed whose monomer units were identified by comparison of their spectra with those of the nonpolymeric molecules. © 1993 John Wiley & Sons, Inc.
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  • 16
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polymer blends ; biodegradable polyesters ; polyanhydrides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Blends of biodegradable polymers having properties distinct from the individual polymer components, and that are suitable for use as carriers of pharmaceutically active agents, were prepared from two or more polyanhydrides, polyesters, and mixtures of polyanhydrides and low molecular weight polyesters. The blends have different properties than the original polymers, providing a mean for altering the characteristics of the polymeric matrix without altering the chemical structure of the component polymers. Aliphatic, aromatic, and copolymers of polyanhydrides were miscible in each other and formed less crystalline compositions with a single melting point which was lower than the melting point of the starting polymers. The polyesters: poly(lactide-glycolide), poly(caprolactone), and poly(hydroxybutyric acid) presented some miscibility in each other. However, the polyanhydrides were immiscible with the polyesters resulting in a complete phase separation both in solution or in melt mixing. Only low molecular weight polyesters (in the range of 2000) of lactide and glycolide, mandelic acid, propylenefumarate, and caprolactone presented some miscibility with polyanhydrides. Similarly, poly(orthoester) and hydroxybutyric acid polymers formed a uniform mixture with the anhydride polymers which had the two melting points of the original polymers. Drug release from polymer blends composed of poly(hydroxybutyric acid) or low molecular weight poly(lactic acid) with poly(sebacic anhydride) (PSA) showed a constant release of drug for periods from 2 weeks to several months as a function of the PSA content in the blend. Increasing the content of PSA, a fast degrading polymer, increases the release rate from the blend. © 1993 John Wiley & Sons, Inc.
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  • 17
    ISSN: 0887-624X
    Keywords: polyimides ; high temperature ; anhydrides ; thermooxidative stability ; 4 atm testing at 371°C ; 1 atmosphere testing at 371°C ; isothermal tests ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a novel polyimide (3F-PDA) derived from 4,4′-(2,2,2-trifluoro-1-phenylethylidene]bisphthalic acid anhydride or its diethyl ester and p-phenylene diamine is described. This material shows unique thermooxidative stability compared with commercially available state-of-the-art polyimides. The optimum monomer stoichiometric ratios of diester to diamine to form a stable 3F-PDA polyimide were investigated. The studies revealed that diester/diamine ratios greater than 1.000 exhibited the greatest resistance to thermooxidative stability at 371°C in 1 atm of circulating air and at 371°C in 4 atm of flowing air. © 1993 John Wiley & Sons, Inc.
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  • 18
    ISSN: 0887-624X
    Keywords: blends ; hydrogen bonding ; miscibility ; phase behavior ; equilibrium constants ; fluoropolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical calculations of miscibility windows for binary polymer blends in which one component is an essentially alternating copolymer of tetrafluoroethylene and vinyl alcohol (FVOH) are reported. FVOH has an inherently low solubility parameter [≈ 6.2 (cal. cm-3)0.5] that is outside the range commonly encountered in miscible polymer blends and thus represents a stringent test of the predictive capabilities of an association model we have used in previous work. The application of this model requires that we determine dimensionless equilibrium constants describing the self-association of a model compound 3,4-pentafluorobutan-2-ol (PFB) at 25°C from infrared spectroscopic data. Analogous equilibrium constants for FVOH were scaled from those of PFB by taking into account differences in the molar volume of the model and the specific repeat of the copolymer (see M. M. Coleman, J. F. Graf, and P. C. Painter: Specific Interactions and the Miscibility of Polymer Blends, Technomic, Lancaster, PA, 1991). Equilibrium constants describing the inter-association of FVOH with ester type carbonyl groups were obtained from spectroscopic studies of miscible blends with poly(ethyl methacrylate). These equilibrium constant values were then used to calculate theoretical miscibility windows for the complete range of blends of FVOH with polymethacrylates, ethylene-co-methyl acrylate, styrene-co-methyl acrylate, and ethylene-co-vinyl acetate copolymers. Experimental results performed in our laboratories confirm the general validity of the predicted miscibility windows. © 1993 John Wiley & Sons, Inc.
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  • 19
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: copolyimides ; pyromellitic dianhydride ; oxydiphthalic dianhydride ; 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl ; synthesis ; film ; tensile properties ; oxidative stability ; water absorption ; hydrolytic stability ; electrical properties ; coefficient of linear thermal expansion ; block copolymer ; blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of transparent copolyimides were prepared from PMDA-ODPA-TFDB via chemical imidization of the corresponding poly(amic acid)s. Copolyimides containing less than 70% PMDA were completely soluble in DMAc and other amide solvents and gave ductile films with unexpectedly high tensile moduli (up to 8.9 GPa). Water absorption, after boiling in water for 72 h, were less than 1 % for the copolymer with 67% PMDA and less than 0.5% for copolymers with less PMDA. Thermooxidative stability was comparable to a commercial polyimide film up to 325°C. A copolyimide containing 34% PMDA had the best overall properties based on the above tests. Additional evaluations revealed a coefficient of linear expansion of about 6 X 10-6/°C, an essentially frequency independent dielectric constant of 2.8, a dissipation factor of about 0.004-0.01 over the range of 1-1000 kHz, and complete retention of tensile properties after exposure to a humid environment for 16 weeks. A model compound study suggests the probable presence of short blocks in these copolymers. © 1993 John Wiley & Sons, Inc.
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  • 20
    ISSN: 0887-624X
    Keywords: liquid crystalline polymer ; thermotropic polyesters ; nematic ; x-ray diffraction ; synthesis ; characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of fully aromatic thermotropic polyesters based on mono-, di-, and tetra-substituted biphenols was prepared by the melt polycondensation method and examined for their thermotropic behavior by a variety of experimental techniques. The homopolyesters obtained from substituted biphenols containing either one phenyl or two phenyl groups as substituent(s) and TA formed nematic melts, but the homopolymers of the substituted biphenols containing either four sec-butyl groups or two tert-butyl groups with TA had melting transitions, Tm, above 400°C. Thus, it was not possible to determine whether they formed nematic melts. On copolymerization with 30 mol % HBA most of the resulting copolyesters had much lower Tm values, compared to those of respective homopolyesters, and the copolymers of the biphenol monomer containing the tert-butyl groups formed a nematic melt at an observable temperature. However, the copolymer of the biphenol with sec-butyl groups still had a Tm above 400°C. © 1993 John Wiley & Sons, Inc.
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  • 21
    ISSN: 0887-624X
    Keywords: IPN's ; poly(chloroprene) ; PCU ; scanning electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simultaneous interpenetrating polymer networks (SIN's) of poly(chloroprene) (CR) and poly(carbonate-urethane) (PCU) were prepared and characterized. The effect of composition on the phase morphology of full IPN's of CR/PCU has been studied by DSC and SEM. A single phase morphology of IPN's has achieved when the content of CR component is below 50 wt %. The microphase separation of the component networks in the IPN's occurred in samples whose weight percentage of the CR component was 50% and higher. © 1993 John Wiley & Sons, Inc.
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  • 22
    ISSN: 0887-624X
    Keywords: radical polymerization ; ring-opening polymerization ; elimination polymerization ; bifunctional monomer ; 1,3-dioxolane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 23
    ISSN: 0887-624X
    Keywords: poly(vinylpyrene) ; substitution ; photochemical and photophysical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of functionalized linear poly(1-vinylpyrene) (PVP) polymers bearing substituents such as —NO2, —CHO, —NH2, —Br, and —CH=C(CN)2, were prepared by chemical modification of PVP in solution. The degree of substitution in PVP—CH=C(CN)2 was varied from 40% to nearly 100% by control of the reaction conditions. The other polymers were partially functionalized. The UV-visible and fluorescence spectroscopy of the polymers were studied in solution. The influence of solvent polarity, excitation energy, and degree of substitution on the fluorescence of the polymers were examined. © 1993 John Wiley & Sons, In
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  • 24
    ISSN: 0887-624X
    Keywords: bis(p-hydroxyphenyl) dimethylsilane ; bisphenol A ; polycarbonates ; outdoor weathering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycarbonates and copolycarbonates based on BPSi and BPA were easily made using the standard interfacial technique. Molecular weight and NMR data indicate that up to 4 mol % of the BPSi decomposes during polymerization via a base-catalyzed rearrangement of BPSi to arylsiloxanes. Oxygen index studies show an increased flame resistance with increasing BPSi monomer content. DSC measurements show a decrease in glass transition with BPSi monomer concentration while TGA shows an increase in char residue with BPSi monomer content. In addition, TGA indicates no change in either thermal or thermooxidative stability with the relative BPSi/BPA concentrations. Outdoor weathering of BPSi PC and BPA PC films indicates that BPSi PC is ca. 5 times more weathering resistant than BPA PC. This latter result can be attributed to a combination of BPSi PC's lower UV absorptivity, higher water repellency, and lower likelihood for side chain photooxidation. © 1993 John Wiley & Sons, Inc.
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  • 25
    ISSN: 0887-624X
    Keywords: liquid crystalline ; liquid crystal polymer ; liquid crystal thermoset ; thermoset ; epoxy ; thermotropic ; networks ; nematic ; smectic ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new epoxy monomers have been synthesized and characterized as part of a program to prepare novel liquid crystal thermoset (LCT) materials. Three of the new epoxy monomers contained a biphenyl mesogen and were not liquid crystalline (LC). The remaining epoxy monomer, which contained a 1,4-dibenzoyloxybenzene mesogen, was synthesized in an overall yield of 30% and displayed a broad (83°C) nematic liquid crystalline phase. The new liquid crystalline epoxy monomer was cured at 120°C and postcured at 175°C with a stoichiometric amount of 1,4-phenylenediamine. The thermal transitions of the resulting LCT were studied by differential scanning calorimetry (DSC), polarized light optical microscopy (POM), thermomechanical analysis (TMA), and wide angle x-ray diffraction (WAXD) as a function of cure time and temperature. A process characterization diagram was constructed which shows that LCTs based on this new LC monomer can be processed in the liquid crystalline phase over a broad range of times and temperatures. Qualitative agreement with previous epoxy LCT results was found, as LCT's with smectic phases and without clearing temperatures were observed at long cure times (high crosslink densities), whereas nematic phases with clearing temperatures predominated in networks at short cure times (low crosslink densities). © 1993 John Wiley & Sons, Inc.
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  • 26
    ISSN: 0887-624X
    Keywords: polyimides ; addition-type polyimides ; thermo-oxidative stability ; Diels-Alder addition polymers ; anthracene-end-capped polyimides ; fluorinated polyimides ; high-temperature polyimides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Diels-Alder addition-type copolymers prepared from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracence and anthracene end-capped 6F-PDA imide oligomers were characterized. The composition of the anthracene end-capped imide oligomers was found to be sensitive to monomer molar ratios and the mode of monomer addition. The resistance of the copolymer to thermooxidative degradation at 316 and 371°C was compared with a similar commercial polymer called Avimid-N prepared from 4,4′-hexafluoroisopropylidene-2,2′ bis(phthalic acid anhydride) and para-and meta-phenylene diamine, abbreviated 6F-PDA. There are strong indications that the copolymers undergo degradation initially by unzipping the diepoxyanthracene unit from the anthracene end-capped 6F-PDA oligomer unit (Avimid-N like repeat unit), followed by a slower degradation of the more stable residual 6F-PDA unit. © 1993 John Wiley & Sons, Inc.
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  • 27
    ISSN: 0887-624X
    Keywords: polystyrene ; bis(vinylphenyl)ethane ; bis(vinylbenzyloxi)alkanes ; mechanical strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of some divinyl monomers - bis(vinylphenyl)ethane (2), bis(vinylbenzyloxy)hexane (3a), and bis(vinylbenzyloxy)dodecane (3b) is reported. Copolymers of the new monomers and styrene were evaluated as an alternative to divinylbenzene-crosslinked polymers for use as matrices and absorbents. The mechanical properties and the amount of residual double bonds in the copolymers were compared. It was found that the new copolymers, unlike the divinylbenzene-crosslinked polymers, retained their mechanical strength even at high crosslinking degrees. Stress at break values of 79, 68, and 18 N/mm2 were found for the polymers crosslinked with 20 mol % of 3a, 2, and divinylbenzene; 5, 25 and 45% of the divinyl units in these polymers were left as pendant double bonds. Porous styrene-2 copolymers were synthesized and shown to have lower surface areas than the corresponding divinylbenzene-crosslinked polymers. The pore size distribution showed that this was due to the absence of the smallest pores which are found in the divinylbenzene-crosslinked polymers in between heavily crosslinked nodules. © 1993 John Wiley & Sons, Inc.
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  • 28
    ISSN: 0887-624X
    Keywords: polyimides ; alicyclic diamines ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polyaddition reactions of alicyclic diamines such as 1,4-diaminocyclohexane (1,4-CHDA) or 4,4′-diaminodicyclohexylmethane (DCHM) and configurational isomers of 1,4-CHDA or DCHM with tetracarboxylic aromatic anhydrides in aprotic solvents were carried out to prepare high molecular weight poly(amic acid)s. Through the thermal imidization of poly(amic acid)s, several flexible polyimide films were prepared. Because of the stiffness of the alicyclic moieties in diamines, the resulting polyimides exhibit high glass transition temperatures (220-340°C) almost similar to those for corresponding aromatic polyimides which have phenylene groups in place of cyclohexyl groups, and show good thermal stability. The partial crystallization was observed for polyimides with trans-cyclohexyl moiety during the heating in differential scanning calorimetry and ascertained by wide-angle x-ray diffraction. Thus, the inhibition of the occurrence of charge transfer in polyimides is accomplished by introducing alicyclic diamines in place of aromatic diamines without reducing their thermal stability. © 1993 John Wiley & Sons, Inc.
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  • 29
    ISSN: 0887-624X
    Keywords: ,α, ω-di(tert-chloro)polyisobutylenes ; 1,4-di(2-propyl-2-hydroxy)cyclohexane ; living carbocationic polymerization ; isobutylene ; inifer efficiency (Ieff) ; telechelics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 30
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; radicals per particle ; prediction methods ; timedependent population ; distribution functions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 31
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 32
    ISSN: 0887-624X
    Keywords: Ziegler-Natta ; polymerization of ethylene ; high temperature ; kinetics ; vanadium ; oxidation state ; deactivation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of the polymerization of ethylene initiated by heterogeneous vanadium-based Ziegler-Natta catalysts (VCI3-1/3 AICI3) have been studied at high temperature (160°C, 5 bars) and compared with a titanium-based system. For the V catalyst, the dependence of the polymerization activity versus time, with the nature and the concentration of the associated aluminum alkyl, has been investigated. Kinetic results have also been correlated with the oxidation state of vanadium in the polymerization conditions. Despite the relatively high initial activity a low productivity is obtained; it can be attributed to a very fast deactivation of the active sites due to the reduction of vanadium III into vanadium II. The effect of the nature of the alkyl aluminum component of the catalytic system on the reduction process is shown. A kinetic model for the polymerization is proposed. © 1993 John Wiley & Sons, Inc.
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  • 33
    ISSN: 0887-624X
    Keywords: interpenetrating polymer networks ; poly(dimethylsiloxane-urethane) ; poly(methyl methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simultaneous IPNs of poly(dimethyl siloxane-urethane) (PDMSU)/poly(methyl methacrylate) (PMMA) and related isomers have been prepared by using new oligomers of bis(β-hydroxyethoxymethyl)poly(dimethyl siloxane)s (PDMS diols) and new crosslinkers biuret triisocyanate (BTI) and tris(β-hydroxylethoxymethyl dimethylsiloxy) phenylsilane (Si-triol). Their phase morphology have been characterized by DSC and SEM. The SEM phase domain size is decreased by increasing crosslink density of the PDMSU network. A single phase IPN of PDMSU/PMMA can be made at an Mc = 1000 and 80 wt % of PDMSU. All of the pseudo- or semi-IPNs and blends of PDMSU and PMMA were phase separated with phase domain sizes ranging from 0.2 to several micrometers. The full IPNs of PDMSU/PMMA have better thermal resistance compared to the blends of linear PDMSU and linear PMMA. © 1993 John Wiley & Sons, Inc.
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  • 34
    ISSN: 0887-624X
    Keywords: oligocyclosiloxanes ; hydrosilation ; heptamethylcyclotetrasiloxane ; siloxane redistribution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of oligocyclosiloxanes via hydrosilation reactions has been investigated. Hydrosilation reactions employing heptamethylcyclotetrasiloxane and vinyl-containing silanes and siloxanes yielded a variety of oligocyclosiloxanes with various numbers of cyclosiloxane rings connected through tri-, tetra-, penta-, hexa-, hepta-, or octafunctional junctions. The oligocyclosiloxanes were characterized by gas chromatography, IR spectroscopy, 29Si-, 1H-, and 13C-NMR spectroscopy, elemental analysis, and vapor phase osmometry. The polycyclics were redistributed with hexamethyldisiloxane and the resulting fragments analyzed by gas chromatography. All results were consistent with the formation of isomeric oligocyclosiloxanes due to a lack of absolute regioselectivity of the hydrosilation reaction. © 1993 John Wiley & Sons, Inc.
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  • 35
    ISSN: 0887-624X
    Keywords: polyimides ; gas separation membranes ; permeability ; ortho-substituted aromatic diamines ; oxygen/nitrogen separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Permeability measurements for oxygen and nitrogen were carried out on a series of structurally similar polyimides in order to define structure/permeability relationships. The polyimides were prepared from 5,5′-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] bis-1,3-isobenzofuranedione (6FDA) and a variety of substituted methylene dianilines and benzidines. A correlation between the diamine monomer structure and polymer permeability was found, particularly with diamine monomer variations at the ortho positions of the diamine relative to the amino moiety. These correlations were semilogarithmic, relative to the summation of the substituent volumes. Direct correlations were observed between the measured properties of polymer density and interchain d-spacings and the oxygen permeability value of each of these polyimides. In addition, we observed that the calculated values of fractional free volume were related to oxygen permeability in a manner which enabled us to identity a polar component in the effects of these ortho substituents. © 1993 John Wiley & Sons, Inc.
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  • 36
    ISSN: 0887-624X
    Keywords: [o-(trimethylgermyl)phenyl]acetylene ; group 6 transition metal catalyst ; living polymerization ; substituted polyacetylene ; gas permeability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [o-(Trimethylgermyl)phenyl]acetylene was polymerized in the presence of WCl6, W(CO)6-hv, etc., to give polymers whose weight-average molecular weights reached ca. 7.0 X 105 at the highest. When the MoOCl4-n-Bu4Sn-EtOH (1 : 1 : 1) catalyst was used, the polydispersity ratio of the polymer obtained was 1.08, and the number-average molecular weight increased in direct proportion to monomer conversion; these indicate that this polymerization is a living polymerization. The polymer had the structure — [CH=C(C6H4-o-GeMe3)]n — and was a dark purple solid (λmax = 551 nm, εmax = 6100 M-1 cm-1 in THF) soluble in organic solvents such as toluene and chloroform. The onset temperature of weight loss of the polymer in TGA in air was ca. 230°C, and the glass transition temperature was above 180°C. The Po2 of the present polymer is 105 barrers - larger than the value of natural rubber and fairly close to that of poly(dimethylsiloxane). © 1993 John Wiley & Sons, Inc.
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  • 37
    ISSN: 0887-624X
    Keywords: comonomer effect ; titanium catalysts ; vanadium catalysts ; electron-donors ; active sites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-activity titanium- and vanadium-based catalysts for ethylene polymerization frequently show an increase in reaction rate in the presence of an α-olefin. The magnitude of this increase depends on the specific α-olefin. The results show propylene 〉 1-butene 〉 1-hexene in increasing initial reaction rates. Addition of certain electron-donor compounds to these catalysts can lower the magnitude of the comonomer effect and, in some cases, totally eliminate such an effect. Among the classes of electron-donor compounds examined were ether-alcohols, ether-esters, amino-alcohols, alkoxysilanes, siloxanes, and phosphine oxides. Reaction kinetics show that the presence of a comonomer can influence the kinetic order of the reaction. These results can be interpreted using a mechanistic model involving two vacant coordination positions at the active sites. In this model electron donors and comonomers are viewed as Lewis-base ligands which influence features of chain propagation and chain termination. As Lewis-base ligands, the comonomers can also increase the number of active sites available for polymerization. Catalyst deactivation following the initial comonomer rate increase is believed to be caused by reaction with the Lewis bases (α-olefin included) in the system and by possible reduction in the oxidation state of the metal centers. The most acidic metal centers activated by the comonomer are most reactive to Lewis bases and deactivate most rapidly. Veratrole (1,2-dimethoxybenzene) can be employed as a probe for estimating the number of bis-vacant coordination sites in vanadium-based catalysts. Addition of low levels of veratrole led to significant deactivation of the vanadium-based catalyst. © 1993 John Wiley & Sons, Inc.
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  • 38
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 39
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 40
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 41
    ISSN: 0887-624X
    Keywords: in-situ ; direct polycondensation ; styrene-butadiene block copolymers aromatic polyester ; composites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct polycondensation of 3-substituted-4-hydroxybenzoic acid was carried out in solutions of styrene-butadiene block copolymers (SBS) at room temperature in the presence of triphenylphosphine and hexachloroethane as an initiator for the direct polycondensation of these monomers. Solution casting after the direct polycondensation provided opaque films in which the aromatic polyester was finely dispersed within the matrix of SBS. Mechanical properties of these films were examined by tensile tests. A great improvement of tensile strength was achieved by the incorporation of phenyl substituent in the resulting polyester. In-situ direct polycondensation leads to the formation of new composites of rigid polymers and flexible polymers. © 1993 John Wiley & Sons, Inc.
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  • 42
    ISSN: 0887-624X
    Keywords: bisimido-bisphthalonitrile ; heat-resistant polymers ; synthesis ; thermosetting ; infrared analysis ; thermal analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heat-resistant polymers which are processable into void-free components and suitable for composite applications have been synthesized by thermal/chemical polymerization of four newly developed bisimido-bisphthalonitriles containing silicon, ether, carbonyl, and hexafluoroisopropylidene groups. Thermal polymerization involving addition reactions was performed at 200-275°C for 2-10 h and then post-curing at 310°C for 10 h. Polymers VI, VII, VIII, and IX were obtained. The thermal polymerization was monitored using infrared spectroscopy. Thermal polymerization was also carried out in the presence of an aromatic diamine. A polyhexasocyclane (V) was synthesized by condensation polymerization of ether containing bisimido-bisphthalonitrile with 4,4′-diaminodiphenyl ether in solvent phenol. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). Polymers VII, VIII, IX, and X showed thermal decomposition temperature in the range of 475-500°C in nitrogen and air atmosphere. The char yield of the polymers was in the range of 60-69% in nitrogen at 800°C. This study indicated that synthesized thermosetting polymers from ether and keto containing bisimido-bisphthalo-nitrile are potential candidates for development of graphite composites. © 1993 John Wiley & Sons, Inc.
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  • 43
    ISSN: 0887-624X
    Keywords: polystyrene ; sorption ; desorption ; evaporation ; polymer-inclusion complexes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results obtained in time studies that monitored evaporation from liquid-saturated poly(styrene-co-divinylbenzene) to virtual dryness at temperatures ranging from 20 to 80°C confirm those reported earlier for multireplicated time studies at 23 ± 1°C; i.e., when the residual composition (αt, in sorbed molecules per phenyl group) attains the glassy state composition, the value of αt thereafter is given by a linear combination of no more than six exponential decay functions. The logarithms of the rate constants (ki) for decay of these populations at a given temperature decreased linearly with i, the population identification number in the order of decreasing decay rate. The Arrhenius activation energy (ΔEi) for increase in ki with temperature was characteristic of the sorbed species, but it was independent of i. The logarithms of the frequency factors (Ai) decreased linearly with i, the slope of which was numerically equal to that observed for the corresponding ki relationships, signifying that the stepwise decrease of the latter at a given temperature is attributable primarily to a corresponding incremental decrease in entropy. It is suggested that this reflects discrete changes in the molecular structure of polymeric inclusion complexes formed during the transition from the rubbery to the glassy state, as discussed in the text. © 1993 John Wiley & Sons, Inc.
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  • 44
    ISSN: 0887-624X
    Keywords: fluorescent probes ; cure monitoring ; laser initiated polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new fluorescence probes useful for following photopolymerization have been characterized. Among these are probes which can be used in rapidly gelling monomer mixtures and for photochemical polymerization initiated by very high laser powers. Systems which can be used with polyolacrylates and either with visible initiators or with UV initiators are reported. © 1993 John Wiley & Sons, Inc.
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  • 45
    ISSN: 0887-624X
    Keywords: poly(ether sulfone) ; sodium sulfonate group ; aromatic nucleophilic substitution ; thermal degradation ; glass transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(ether sulfone)s containing pendant sodium sulfonate groups were prepared by the aromatic nucleophilic substitution reaction of 4,4′-dichlorodiphenylsulfone (1) and sodium 5,5′-sulfonylbis (2-chlorobenzenesulfonate) (2) with bisphenols (3) in the presence of potassium carbonate in N,N-dimethylacetamide. A new monomer 2 containing the sodium sulfonate groups was synthesized by the sulfonation of 1 with fuming sulfuric acid. The polycondensation proceeded smoothly at 170°C and produced the desired poly(ether sulfone)s containing the sodium sulfonate with inherent viscosities up to 1.2 dL/g. The polymers were quite soluble in strong acid, dipolar aprotic solvents, m-cresol, and dichloromethane. The thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight losses of the polymers were observed in the range above 460°C in nitrogen atmosphere. Both the glass transition temperatures and hydrophilicity of the polymers increased with increasing their concentrations of sodium sulfonate groups. © 1993 John Wiley & Sons, Inc.
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  • 46
    ISSN: 0887-624X
    Keywords: isomeric 4,4‴-dichloroquaterphenyls ; Ni(0)-catalyzed oligomerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,4‴-Dichloro-1,1′ : 2′,1″ : 2″,1‴-quaterphenyl (9), 4,4‴-dichloro-1,1′ : 3′,1″ : 3″,1‴-quaterphenyl (10), and 4,4‴-dichloro-1,1′ : 4′,1″ : 4″,1‴-quaterphenyl (11) were synthesized by Pd (0) catalyzed cross-coupling reaction of 4-chlorobenzeneboronic acid with 2,2′-, 3,3′-, and 4,4′-bis (trifluoromethanesulfonyloxy)biphenyl respectively. 4,4‴-Dichloro-1,1′ : 2′,1″ : 2″,1‴-quaterphenyl (9) and 4,4‴-dichloro-1,1′ : 3′,1″ : 3″,1‴-quaterphenyl (10) were oligomerized by Ni(0) catalyzed homocoupling reaction to yield white and soluble oligophenylenes. © 1993 John Wiley & Sons, Inc.
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  • 47
    ISSN: 0887-624X
    Keywords: radical polymerization ; monomer-isomerization polymerization ; dialkyl maleate ; substituted polymethylene ; poly(fumaric acid) ; pyrolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Di-tert-butyl maleate (DtBM) did not polymerize with 2,2′-azobis(isobutyronitrile) as a radical initiator, but DtBM easily homopolymerized via a monomer-isomerization radical polymerization mechanism to give a high molecular weight polymer when morpholine was added into the polymerization system as an isomerization catalyst. The feature of the monomer-isomerization polymerization of DtBM was investigated in detail. The polymer obtained was confirmed to consist of a poly(tert-butoxycarbonylmethylene) structure similar to that from di-tert-butyl fumarate. Subsequent pyrolysis of the resulting polymer at 180°C is a useful route to synthesis of a high molecular weight poly(fumaric acid). © 1993 John Wiley & Sons, Inc.
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  • 48
    ISSN: 0887-624X
    Keywords: ethyl 3-oxo-4-pentenoates ; 4-vinyl pyridine ; complex formation ; copolymerization ; solvent effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 49
    ISSN: 0887-624X
    Keywords: aromatic polyhydrazides ; heat-resistant polymers ; synthesis ; thermal analysis ; structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new aromatic polyetheraroylhydrazides incorporating 4-oxybenzoyl units has been synthesized, whose general formula was [CONHNHCO—O—O-(CH2)x—O—phenyl O-CONHNHCOO]n with x values in the range of 2 to 12. The increasing number of methylene units in the backbone gave rise to polymers which melted before the hydrazidic linkage underwent thermal cyclation to oxadiazole. Moreover, many polymers showed multiple endotherms on melting. X-ray diffraction studies confirmed a crystalline organization of polyhydrazides for methylene units above 4. © 1993 John Wiley & Sons, Inc.
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  • 50
    ISSN: 0887-624X
    Keywords: copolymerization ; antipyryl acrylamide ; antipyrine acryloyl thiourea ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 51
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 52
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 53
    ISSN: 0887-624X
    Keywords: polyurethanes ; non-linear optics ; second harmonic generation ; poling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of six diol and one triol monomers bearing donor-acceptor chromophores is described. The monomers contain the N,N′-bis(2-hydroxyethyl)aniline unit with various acceptor groups attached in some cases via azo or olefin linkages, at the para position. Acceptors studied include nitro, tricyanovinyl, cyclobutene-1,2-dione, and imidazolidine-2,4-dione. Poled polymer films were prepared by thermal polymerization of these with 2,4-toluenediisocyanate (TDI) in the presence of an electric field generated by a corona tip. The resulting thin (ca. 1 μm), glassy polymer films were shown to exhibit reasonably good second harmonic generation efficiencies. Preliminary results show that the polymers with higher Tg's have the best temporal stability. The polymer derived from the diol bearing an imidazolidine-2,4-dione acceptor shows only a ca. 30% decrease in its second harmonic generation (SHG) signal over 200 days at room temperature, even though it is not crosslinked. We attribute this to hydrogen bonding interactions from the urethane and imidazolidine-2,4-dione groups. A crosslinked film derived from the triol and TDI has an exceedingly stable SHG response at room temperature, and no decrease in the SHG response is observed at 100°C for a few hours. © 1993 John Wiley & Sons, Inc.
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  • 54
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: radicals ; low temperature ; sulphur dioxide copolymerization ; ESR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Free radicals generated from a number of olefinic, acetylenic, and vinyl monomers in the presence of sulphur dioxide and tert-butyl hydroperoxide were investigated. In all reaction systems a sulphonyl propagating radical first appears which depropagates into the corresponding carbon radical at higher temperatures. The sulphonyl radicals were observed between -119 and -44°C, whereas the carbon radicals were observed from -63 to -1°C. The order of decreasing reactivity of the reaction system was: 3-hexyne 〉 1-heptene 〉 methyl acrylate 〉 acrylonitrile 〉 1-heptyne. © 1993 John Wiley & Sons, Inc.
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  • 55
    ISSN: 0887-624X
    Keywords: emulsion polymerization, role of particle/water interface ; vinyl acetate, emulsion copolymerization ; copolymerization in emulsion, mathematical model ; mathematical model, vinyl acetate/reactive surfactant emulsion copolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mathematical model was developed to aid in the further understanding of the growth of latex particles in the emulsion polymerization of vinyl acctate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40). The model incorporates the main features of the system observed experimentally: copolymerization in the aqueous phase, at the particle surface, and chain transfer to TREM LF-40. The reactions at the particle/water interface and, more specifically, the chain transfer to TREM LF-40 leading to a decrease in the average number of radicals per particle, was found to be the most significant mechanism for explaining the difference in kinetic results found for TREM LF-40 and its nonpolymerizable counterpart. The copolymerization of vinyl acetate with TREM LF-40 was also shown to slow the overall polymerization rate. However, the copolymerization alone was not sufficient to account for the decreased polymerization rates observed experimentally. A combination of copolymerization and chain transfer to TREM LF-40 was found to provide a good fit of the experimental results. © 1993 John Wiley & Sons, Inc.
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  • 56
    ISSN: 0887-624X
    Keywords: graft copolymerization ; graft copolymers ; potato starch ; methyl acrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO3) (1.08, 5.0 × 10-3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: Rp = Kkd [STOH] [Ce4+] + Kkpkd/kt[STOH][M], where K, kd, kp, and kt are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc.
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  • 57
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: monoisocyanates ; butyl isocyanate ; polymerization ; trimerization ; Pruitt-Baggett adduct ; PBA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: n-Butyl isocyanate (nBIC) was polymerized in bulk by the Pruitt-Baggett adduct (PBA) at -23, 0.0, and 25.0°C. Polymerization was accompanied by trimerization to the cyclicisocyanurates at all temperatures. Spectroscopic evidences supported the nylon-1 structure for both trimer and polymer. The polymer/trimer ratio and the molecular weight of produced polymers were found to increase with decreasing temperature. The Pruitt-Baggett catalyst (PBC), which is the reaction product of (PBA + H2O) system, also polymerized nBIC, but with a relatively slower rate. In aromatic and etheric solutions, nBIC was only trimerized by PBA. Copolymerization of nBIC with propylene oxide by PBA and PBC failed. Some selected monoisocyanates were also polymerized by PBA. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    ISSN: 0887-624X
    Keywords: quinone methides preparation ; anionic homopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 7-Phenyl-, 7-chlorophenyl-,7-methylphenyl-, and 7-trifluoromethylphenylquinone methide were synthesized to investigate the anionic polymerization of quinone methide. Novel high molecular weight polymers have been prepared and the substitution effects of the monomers on polymerization kinetics were determined. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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