Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Polymer and Materials Science  (3,750)
  • 1990-1994  (3,750)
  • 1985-1989
  • 1970-1974
  • 1992  (3,750)
Collection
Publisher
Years
  • 1990-1994  (3,750)
  • 1985-1989
  • 1970-1974
Year
  • 1
    ISSN: 0887-624X
    Keywords: bis-amide-imides ; poly-bismaleimides ; poly-biscitzaconimides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0887-624X
    Keywords: new synthetic method ; two-step synthesis ; polybenzothiazoles ; aromatic diacid chlorides ; 2,5-bisalkylthio-1,4-phenylenediamine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel two-step method for the synthesis of polybenzothiazoles has been developed starting from 2,5-bis(isoprophylthio)-1,4-phenylenediamine and aromatic dicarboxylic acid chlorides. The low-temperature solution polycondensation of these monomer pairs in N-methyl-2-pyrrolidone afforded the aromatic polyamides with pendant isopropylthio groups having inherent viscosities in the range of 0.8 and 2.4 dL/g. The soluble precursor polyamides were subjected to thermal cyclization to the corresponding polybenzothiazoles along with the elimination of propylene and water. The resulting polymers were also characterized.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0887-624X
    Keywords: polyarylate ; acidolysis ; kinetics ; mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model reactions were carried out to simulate the acidolysis process for polyarylate synthesis by using p-tert-butylphenyl acetate (ptBuPhOAc) and benzoic acid in diphenyl ether. p-tert-Butylphenol was formed in the reaction mixture and its concentration stayed constant throughout the reaction. Acetic benzoic anhydride and benzoic anhydride were detected by NMR. Based on this experimental evidence, a mechanism for the acidolysis was proposed involving the mixed anhydride. The kinetics of the acidolysis reaction was studied for this model reaction. The overall reaction order is two and the reaction order with respect to each reactant is one. Second-order reaction rate constants were measured at different reaction conditions (200-250°C). The activation energy (Ea), activation enthalpy (ΔH≠), and activation entropy (ΔS≠) were calculated from these data. The thermodynamic parameters of the acidolysis reaction were also measured for the analogous reaction of p-tert-butylphenyl pivalate (ptBuPhOPiv) and benzoic acid. The kinetics of two other elementary reactions involved in the acidolysis reaction were also studied: p-tert-butylphenol with acetic anhydride or benzoic anhydride, and p-tert-butylphenyl pivalate with benzoic acid.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0887-624X
    Keywords: electron beam ; solid-state polymerization ; binary mixture ; methacrylate monomer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-state polymerization of a binary mixture of nonliquid-crystalline monomer and liquidcrystalline compound was carried out using electron beam. The monomers were benzoic acid containing 4-[ω-(meth)acryloyloxyalkyloxy] benzoic acids, in which the alkylene spacer was ethylene, hexamethylene, or undecamethylene. The conversion yield of monomer to polymer to a large extent increased with increasing content of a liquid-crystalline compound with a terminal carboxylic group, such as 4-n-alkyloxybenzoic acid, while the addition of a liquid-crystalline compound without terminal carboxylic group did not affect polymerization of the monomer. Phase diagrams of the mixture of monomer and liquid-crystalline compound were examined using cross-polarizing microscopy and differential scanning calorimetry (DSC). All mixtures of monomer and 4-n-alkyloxybenzoic acid or liquid-crystalline compound without terminal carboxylic group showed liquid-crystallinity in a broad composition range. It was concluded that liquid-crystalline compounds with terminal carboxylic acid may form hydrogen bondings with methacrylate or acrylate monomer having terminal carboxylic acid which enhance polymerizability of the mixture. The stereoregularity of polymers determined by NMR depended on increasing irradiation dose and temperature rather than the content of the added liquid-crystalline 4-n-decanoxybenzoic acid.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: amphiphilic polymers ; graft copolymers ; poly(ethylene glycol) ; GPC ; inverted micelles ; partition chromatography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amphiphilic comb polymers were prepared through grafting poly(ethylene glycol) methyl ether (MPEG 2000) onto acrylic and methacrylic copolymers. The graft copolymers were purified from unreacted MPEG by partition chromatography on methanol pretreated fibrous cellulose using ethyl acetate and methanol as eluents. The separation was found to depend on the water contents of the cellulose and the eluents. It is proposed that one parameter of importance for the chromatographic separation is the formation of hydrated inverted micelles. The amphiphilic comb polymers were shown by gel chromatography on Sepharose to form high molecular weight aggregates in water. On addition of sodium lauryl sulphate or inorganic salts to the eluent at low ionic strengths these aggregates dissociated and were fractionated by the gel. It was also shown that on GPC in THF solution on Styragel columns the polymers exhibited apparent molecular weights equal or smaller than those of the corresponding backbones. This effect may be a consequence of the graft copolymers having relatively small hydrodynamic volumes, and this idea is supported by the fact that their intrinsic viscosities generally were lower than those of the backbones. However, adsorption on the Styragel columns also may be of importance.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0887-624X
    Keywords: plasma-induced radicals ; electron spin resonance (ESR) ; crosslinked methacrylic polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma-induced radicals of several crosslinked methacrylic polymers such as poly(ethyleneglycol dimethacrylate) (PEDMA), poly(2-hydroxyethylmethacrylate) (PHEMA) and polymethacrylamide (PMAAm) were studied by electron spin resonance (ESR). The observed ESR spectra did not exhibit a drastic difference in the spectral feature caused by the effect of crosslinking. All the spectral features can be represented by “nine-line spectra” as a major spectral component similar to those of linear methacrylic polymers such as polymethacrylic acid (PMAA). A pronounced effect of crosslinking, however, has emerged on the specific formation in the radical structure and the stability of radicals formed, especially in PEDMA. The formation of fewer kinds of radical in PEDMA is apparently caused by the high degree of crosslinking which leads to a suppression of the occurrence of depolymerization on plasma irradiation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0887-624X
    Keywords: inorganic polymer ; silicic acid ; polytitanosiloxane ; SiO2-TiO2 ; oxide fibers ; tensile strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From polytitanosiloxanes (PTS), SiO2-TiO2 oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polyethylene ; polypropylene ; oxidation ; biodegradation ; C—H bond activation ; functionalization ; XPS ; ATR-IR ; surface ; Gif ; oxidase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe3O(OCOCH3)6(C6H5N)3.5 and FeCl3 • 6H2O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0887-624X
    Keywords: hydrogenation ; diimide ; p-toluenesulfonylhydrazide ; polybutadiene ; polyisoprene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrogenation of unsaturated polymers with diimide generated in-situ by thermolysis of p-toluenesulfonyl hydrazide (TSH) is a commonly used method for preparing laboratory scale quantities of saturated diene based polymers. The by-products from TSH, particularly p-toluenesulfinic acid, can attack at olefinic sites, adding p-tolylsulfone functionality and degrading polymer molecular weight. The addition of tri-n-propyl amine has been found to eliminate these side reactions in butadiene containing polymers and copolymers, enabling the preparation of polymers devoid of backbone unsaturation. No detectable sulfur-containing impurities were indicated by IR, NMR, or elemental analysis, and no chain degradation was observed via GPC analysis of the hydrogenated polymers. cis-Polybutadiene and butadiene containing random and block copolymers with styrene were hydrogenated cleanly using this technique. A ratio of 2 mol TSH and 2 mol amine/mol of olefin was necessary to assure 〉 99% hydrogenation, and a w/v ratio of 2 parts butadiene/100 parts o-xylene gave the most efficient hydrogenation. Polymers prepared from isoprene were only partially hydrogenated when treated with TSH in the presence of tri-n-propyl amine, and gave evidence of slight degradation of the polymer structure.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 11
    ISSN: 0887-624X
    Keywords: cation-radical ; transalkylation ; aromatic polyether ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and the mechanism of oxidative polymerization of 2,2-bis[4-(1-naphthoxy)phenyl]propane (4) and 2,2-bis[4-(1-naphthyl)phenyl]propane (9) are presented. Both monomers polymerize by two different propagation steps. The first one represents a cation-radical dimerization of the naphthyl groups to dinaphthyl structure. H+[FeCl4]- generated from the first propagation step initiates a transalkylation reaction which provides structural units containing isopropylidenic groups inserted between phenyl and naphthyl, and between two naphthyl groups, respectively. Since the phenyl groups resulted from the second propagation reaction are unreactive in both the oxidative coupling and the transalkylation steps this polymerization reaction leads to polymers with low molecular weights containing phenyl chain ends.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0887-624X
    Keywords: Scholl reaction ; cation-radical polymerization ; 1,5-bis(phenoxy)pentanes ; polymerization mechanism ; polymerizability of monomers ; proton transfer reactions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and the oxidative polymerization of 1,5-bis(phenoxy)pentane, 1,5-bis(phenoxy)pentane substituted with various electron-donating groups, and 1,5-bis(phenylthio)pentane is described. The polymers derived from methyl substituted 1,5-bis(phenoxy)pentane monomers contain diphenyl methane, 1,2-diphenylethane, and benzyl chloride structural units. The mechanism for the generation of these structural units is presented. It consists of the proton transfer reactions from the cation-radical propagating species and subsequent reactions of the resulting benzyl radicals. The polymerizability of monomers with 1,5-pentanedioxy group is lower than that of the monomers with diphenyl sulfone group. This dissimilarity was attributed to the difference between both the reactivity and the concentration of the cation-radical propagating species resulted from these two classes of monomers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 0887-624X
    Keywords: multifunctional copolyamide ; β-truxinate unit ; p-phenylenebis(acrylate) unit ; p-phenylenebis (p-cyanobutadienecarboxylate) unit ; different photosensitive groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolyamides 1,9, and 10 containing both cyclobutane rings and conjugated double bonds in the main chain were synthesized by polycondensation of 1,3-di(4-piperidyl)propane (DPP) with β-truxinate (β-BNPT), with di(p-nitrophenyl) p-phenylenebis(acrylate) (p-NPDA), with di(p-nitrophenyl) p-phenylenebis (α-cyanoacrylate) (p-NPDC), and with di(p-nitrophenyl) p-phenylenebis (α-cyanobutadienecarboxylate) (p-NPDCB) in aprotic polar solvents at room temperature, respectively. Reduced viscosity of copolyamide 1 was strongly affected by the reaction process, the molar ratio of two ester monomers, and reaction time. The copolyamide 1 with the highest viscosity was prepared by the reaction of DPP with 70-50 mol % of β-BNPT for 24 h followed by the polycondensation of the resulting precursor with 30-50 mol % of p-NPDA for 24-96 h. Although copolyamide 9 with high viscosity was not obtained by the polycondensation with β-BNPT and p-NPDC, copolyamide 10 with relatively high viscosity was obtained by the reaction with β-BNPT and p-NPDCB under the same conditions applied for the synthesis of copolyamide 1. The solubility of copolyamides 1,9, and 10 decreased gradually with increasing p-NPDA, p-NPDC, and p-NPDCB units in the copolymers. Furthermore, it was found that copolyamides 1,9, and 10 crosslinked upon irradiation with 313 or 365 nm light, and these copolyamides also decomposed upon irradiation with 254 nm light. That is, the photochemical property of these copolyamides can be controlled by the selection of wavelength of the photoirradiation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: silazane ; oligosilazanes ; polysilazanes ; cyclosilazanes ; phenylendiamines ; transamination ; ring cleavage ; recyclization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heating N,N′-diphenyltetramethylcyclodisilazane with phenylenediamines in the melt at temperatures over 200°C was found to yield oligomers composed of linear and cyclic disilazane units interlinked by phenylene groups. Increasing the temperature of the reaction of meta- and particularly para-phenylenediamine over 300°C promotes formation of crosslinked, infusible, and insoluble polymeric material. The succeeding steps of growth of the polymer molecules, which include cyclodisilazane ring cleavage, transaminations, and recyclizations, have been studied by elemental and spectroscopic analyses of the intermediate low molecular and oligomeric species in the distillable and nonvolatile products of the reactions.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 0887-624X
    Keywords: photoinduced polymerization ; dimethacrylates ; benzophenone ; linear sulfides ; cyclic dithioacetals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoinduced polymerization of butanediol-1,4 dimethacrylate was investigated in the presence of various linear sulfides and cyclic dithioacetals. Benzophenone was used as a sensitizer. It was found that the addition of small amounts of sulfides to the polymerization mixture causes, depending on the sulfide structure and concentration, reduction or full elimination of an induction period as well as an increase in the reaction rate and yield both in air and argon-saturated systems. The explanation of the obtained results is based on the propensity of sulfides to act as hydrogen donors, chain-transfer agents, and highly oxidizable compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 0887-624X
    Keywords: hydrogenation ; nitrile rubber ; rubber ; palladium acetate catalyst ; modification of rubber ; kinetics ; characterization of rubber ; spectroscopic analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenated nitrile rubber was prepared by using palladium acetate as the homogeneous catalyst system. The effect of different reaction parameters on the level of hydrogenation was studied. The extent of hydrogenation increased with increase in reaction time, temperature, pressure, and catalyst concentration. A maximum conversion of 96% could be achieved. The degree of hydrogenation was estimated from IR and NMR spectroscopy. The selectivity of the catalyst in reducing —C=C— in presence of —C≡N was supported by IR and 13C-NMR spectra. ESCA studies further confirmed this observation. Properties of hydrogenated nitrile rubber were investigated by various techniques such as gel permeation chromatography (GPC), glass transition temperature (Tg), stress-strain behavior and rheological measurements. GPC studies showed no significant change in molecular weights of the products after the reaction. Tg value decreased with an increase in the level of hydrogenation. The ultimate stress improved significantly with the increase in the extent of hydrogenation. The die swell decreased with hydrogenation at a particular shear rate. The kinetics of the NBR hydrogenation were investigated. With the increase of the hydrogen pressure and catalyst concentration, the rate of the reaction increased. The reaction was apparently first order with respect to olefinic substrate at higher hydrogen pressure. The apparent activation energy, enthalpy, and entropy of the reaction were calculated as 29.9 kJ/mol, 27.42 kJ/mol, and -0.20 kJ mol-1 K-1, respectively.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 0887-624X
    Keywords: polyethylene ; oxidation products ; gamma ; photo ; thermal ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The detailed oxidation products from the initiated oxidation of linear low density polyethylene have been compared by the use of infrared spectroscopy combined with chemical derivatization. Oxidized films were treated with NO or SF4 to allow the resolution of the various alcohol and hydroperoxides and of the carbonyl species, respectively. All types of initiation gave very similar products but in varying quantities. In photooxidation, hydroperoxide was clearly shown to approach a photostationary concentration either from below for fresh film or from above for samples that had been pre-oxidized by γ-irradiation, prior to UV exposure. Carboxylic acid groups, the main backbone scission product, dominated in photooxidations, possibly as the result of the further oxidation of sec-hydroperoxide sites.
    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: 0887-624X
    Keywords: hydrogel ; beads ; poly(N-isopropylacrylamide) ; LCST ; Ca-alginate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 19
    ISSN: 0887-624X
    Keywords: ring-opening polymerization ; polypropyleneimine ; N-benzyl phthalimides ; thermo-initiated polymerization ; thermal catalyst ; latent catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: chloromethyl styrene ; bis(vinylbenzyl)-ether ; phase transfer catalysis ; 13C CP/MAS NMR ; crosslinking ; styrylmethyl ether ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 21
    ISSN: 0887-624X
    Keywords: ring-opening polymerization ; epoxide polymerization ; cationic polymerization ; transition metal initiators ; cobalt initiators ; dicobaltoctacarbonyl ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of Si—H containing cocatalysts, dicobaltoctacarbonyl has been found to very efficiently catalyze the ring-opening polymerization of cyclic ethers, especially epoxides, as well as certain vinyl monomers. The reaction conditions employed are very similar to those used in Co2(CO)8 catalyzed hydrogenation and hydrosilylation reactions. Detailed investigations have been carried out to elucidate the nature of the active species for this catalytic system. A cationic mechanism is proposed based on the experimental results of those investigations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 22
    ISSN: 0887-624X
    Keywords: thermoplastic elastomer ; carbocationic polymerization ; polyisobutylene ; living polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert-ether (dicumyl methyl ether) initiator in conjunction with TiCl4 coinitiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at -80°C. After the living narrow molecular weight distribution PIB midblock ($\[\bar M_n\]$ = 1.1-1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p-methylstyrene (pMeSt), p-t-butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6-trimethylstyrene (TMeSt) and α-methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N-dimethylacetamide (DMA), TPEs with good mechanical properties (10-20 MPa tensile strength, 300-600% elongation) were prepared. The products exhibit a low and a high temperature Tg characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt-PIB-PSt triblock copolymers due to the higher Tgs (PpMeSt = 108, PptBuSt = 142 and PIn = 220-240°C) of the outer blocks. The Tg of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt-butylstyrene-co-indene) showed a single glassy transition Tg = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end-blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt-PIB-PSt triblock of similar composition.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 23
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: poly(arylether sulfone)s ; poly(aryl sulfone)s ; polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of poly(4-oxy-1,4-phenylenesulfonyl-4,4′-biphenylene-4-sulfonylphenylene) (PBP) has been accomplished by the base mediated, polycondensation reaction between two biphenyl containing monomers. The bisphenol, 4,4′-bis[(4-hydroxyphenyl) sulfonyl]biphenyl (HSB), was reacted with 4,4′-bis[(4-chlorophenyl)sulfonyl]-biphenyl (CSB) in tetramethylene sulfone solvent. The highest mechanical properties and glass transition temperature was observed for polymer PBP with a reduced viscosity around 1.0 dL/g. Consequently, the current synthesis route provides polymer with higher properties than other historical preparative routes. Blends of PBP with a different poly(ether sulfone) were miscible based on the observance of a single glass transition temperature. The Tgs of the polymer blends exhibited an unusual positive deviation from the weighted linear averages of the components.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 25
    ISSN: 0887-624X
    Keywords: monodisperse particles ; emulsion copolymerization, divinylbenzene ; porous particles ; macroporous structure ; linear polymer, diluent ; crosslinked domains ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monodisperse porous polymer particles in the size range of 10 μm in diameter were prepared via seeded emulsion polymerization. Linear polymer (polystyrene seed) or a mixture of linear polymer and solvent or nonsolvent were used as inert diluents. The pore diameters of these porous polymer particles were on the order of 1000 Å with pore volumes up to 0.9 mL/g and specific surface areas up to 200 m2/g. The physical features of the porous polymer particles depended on the diluent type and the crosslinker content, as well as the molecular weight of polymer seed particles. By varying the molecular weight of the linear polymer, monodisperse porous polymer particles with different pore size distribution could be synthesized. Polymer seed with a low degree of crosslinking instead of linear polymer could also be used to prepare monodisperse porous polymer particles with smaller pore volume and pore size.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 26
    ISSN: 0887-624X
    Keywords: telechelic oligomers ; halogenated telomers ; monodispersed α,ω-diols ; redox telomerization of allyl acetate ; α,ω-di(trichloromethyled) end grouped telomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The redox bistelomerization of allyl acetate with telogens which exhibit α, ω-di(trichloromethyled) end groups catalyzed by copper, iron salts, or a ruthenium complex led to monoadducts and telechelic oligomers. These diacetates were quantitatively changed into diols. Such compounds have been characterized by both 1H- and 13C-NMR. A reactivity series has been determined and shows that both end groups must be activated to obtain the expected telechelic products in satisfactory yields.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 27
    ISSN: 0887-624X
    Keywords: facilitated transport ; oxygen permselective membrane ; poly(trimethylsilylpropyne) ; porphyrin polymer ; oxygen carrier ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combination membrane of poly(1-trimethylsilyl-1-propyne) with enormously high permeability and poly(vinylimidazole)-bound porphinatocobalt with selective oxygenbinding ability was prepared. Oxygen transport through the membrane was facilitated in terms of oxygen transport via the latter domain as a fixed oxygen-carrier, and this oxygen permeability maintained for a month.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: bismaleimides ; structure effect ; crosslinking reaction ; heat resistance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel bismaleimides (BMIs) were prepared from functional monomaleimides and diglycidyl ether of bisphenol A (DGEBA) and some of them were shown to have good processibility and improved water resistance while retaining characteristic thermal stability of polyimide. Functional monomaleimides were synthesized via the condensation reaction of maleic anhydride with either aminobenzoic acid or aminophenol. Crosslinking reaction of thus obtained BMIs was carried out with or without catalyst at the temperature range of 100-250°C. The type of the functional group species and their position in monomaleimides significantly affected the crosslinking behavior of the resulting BMIs and the thermal property of their crosslinked products. BMIs with meta linkage, obtained from meta monomaleimides, exhibited much faster thermal crosslinking behavior than corresponding para BMIs. When the molecular weight of BMI was larger, the crosslinking density became smaller and Tg was lower as expected, while the viscosity started to increase at a higher temperature. Glass transition temperatures of the crosslinked resins were in the range of 160-250°C and these resins showed excellent thermal stability up to 370°C.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 29
    ISSN: 0887-624X
    Keywords: emulsion homopolymerization ; molecular weight modeling ; molecular weight distribution ; Markov chains ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for evaluating the instantaneous degree of polymerization distribution of homopolymers produced in emulsion, based on the mathematics of the Markov chains, is developed. The model accounts for any number of active chains per particle, as well as for the two fundamental mechanisms of chain termination: mono- and bi-molecular, both by combination and by disproportionation. The core of the model is the so called subprocessmain process treatment, which allows us to correctly evaluate the degree of polymerization of the chains growing in the polymer particles, by distinguishing between the events experienced by the polymer chain which imply a change of its degree of polymerization (subject transitions) and those which imply only a change in the particle state (environment transitions). This is obtained by properly defining the one-step transition probability matrix of the relevant Markov process. Once this is done, the evaluation of the distribution of the degrees of polymerization reduces to a few simple operations among matrices. Explicit expressions for the instantaneous probability density functions and the relative cumulative distributions are obtained. The application of such relationships is facilitated by the numerical procedures reported in the Appendices. The results of the model developed in this work are in agreement with those of earlier models in the range of parameter values of practical interest. In the limit of very low molecular weights, only the model developed in this work provides the correct answer. Moreover, a much more significant result is its applicability to the case of emulsion copolymerization, as it is shown in Part II.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 30
    ISSN: 0887-624X
    Keywords: emulsion copolymerization ; molecular weight modeling ; molecular weight distribution ; chain composition distribution ; Markov chains ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for evaluating instantaneous degree of polymerization distribution and the chain composition distribution of copolymers produced in emulsion is developed. The approach adopted is based on the mathematics of Markov processes and represents an extension of the one developed for homopolymers in Part I. As in the homopolymer case, the main aspect of the theoretical treatment is the definition of the proper one step transition probability matrix through the so called subprocess-main process procedure. The model accounts for monomolecular and bimolecular termination (both by combination and disproportionation) and, in principle, it can be applied to any number of reacting monomer species as well as to any number of active chains per particle. However, only the 0-1-2 and 0-1-2-3 emulsion copolymerization systems are discussed in detail. In the case of the chain composition distribution, the model allows the calculation of its moments only, through the method of the Generating Function associated with the probability density function. The expression obtained for the instantaneous probability density functions, as well as for the corresponding cumulative distributions, are all in explicit form and involve only algebraic operations among matrices. Efficient numerical procedure for their application are reported in the Appendix. Illustrative calculations are reported for a 0-1-2-3 copolymerization system, simulating the copolymer styrene-methylmethacrylate. The effect of the various termination mechanisms on the distribution of degrees of polymerization and on the first two moments of the chain composition distribution is discussed in detail. Finally, the three dimensional overall distribution function of both chain length and composition is shown under the assumption of Gaussian type chain composition distribution.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: oxazolines ; block copolymers ; polyethyleneimine ; selective hydrolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Block copolymers, composed of a hydrophobic block [poly(N-t-butylbenzoyl ethylenimine) or poly(N-lauroyl ethylenimine)] and a hydrophilic block [poly(N-propionyl ethylenimine)], synthesized by cationic ring-opening polymerization of 2-substituted Δ2-oxazolines, were selectively deacylated by acid hydrolysis. The hydrolysis process was monitored by using 1H-NMR. The results show that the propionyl groups could be removed from the hydrophilic block of the polymer chain without touching the hydrophobic block, if appropriate reaction conditions were used.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 32
    ISSN: 0887-624X
    Keywords: template polymerization ; crosslinked PMAA ; calorimetry ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of crosslinked poly(methacrylic acid) (c-PMAA) on the polymerization of N-vinylimidazole in aqueous solution was studied using UV, calorimetry, SEM, and TEM. It was established that synthetic lightly crosslinked PMAA samples behaved intermediate between rigid crosslinked PMAA particles functioning as microreactors, and linear conventional PMAA, where template and conventional polymerization in the surrounding solution are integrated. A modified calorimetric technique was used to measure monomer conversion, and to correct for the rapid adsorption process. Rate enhancements up to a factor of 4 were obtained for the c-PMAA's, which were lower than those obtained for linear conventional PMAA, and which slightly decreased with increasing crosslink density of the samples. Template complexes possessed a platelet-like morphology similar to template complexes obtained for linear PMAA.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 33
    ISSN: 0887-624X
    Keywords: selective polymerization ; 4-Vinyl-1-cyclohexene ; Ziegler-Natta catalyst ; isomerization ; kinetics ; copolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of 4-vinyl-1-cyclohexene (4VCHE) with Ziegler-Natta catalysts was studied. The polymerization of 4VCHE by the vinyl group took place with TiCl3-aluminum alkyls catalysts, while vinylene group of 4VCHE did not participate in the reaction, but it affected the polymerization rate of 4VCHE. The effects of aluminum alkyl and type of TiCl3 on the polymerization were examined. The overall activation energy for the polymerization was estimated to be 41.9kJ/mol. Monomer-isomerization copolymerization of 4VCHE and trans-2-butene occurred with the TiCl3-(i-C4H9)3Al catalyst to give copolymers consisting of 4VCHE and 1-butene units.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 0887-624X
    Keywords: silphenylene-siloxane polymers ; side chain liquid crystalline polymers ; liquid crystalline polymers ; mesogenic group effects ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Side-chain liquid crystalline (SCLC) silphenylene-siloxane polymers with a phenyl benzoate mesogenic group and polymethylene spacers were prepared and characterized, and their properties were compared with those of equivalent SCLC polymers, SCLCPs, with a biphenyl mesogenic group. With identical spacers and terminal substituents, the melting temperatures of the former were much lower, but the isotropization temperatures were lowered to a lesser extent, than those of the latter, and, consequently, a more thermally stable nematic phase was obtained for the former. Both types of SCLCPs formed nematic phases, while polymethylsiloxanes with the same side-chain mesogens exhibited smectic phases with wider temperature ranges. The lower thermal stability of the mesophases in the silphenylene-siloxane SCLCPs compared to those of the SCLC polymethylsiloxanes can be attributed to both the rigidity of the backbone and the greater separation of the side-chains along the main chains of the former.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 0887-624X
    Keywords: UV-curable resin ; flame-retardant monomer ; bromine phosphorus synergism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV-curable urethane acrylate resin and oligoester acrylate resin have been effectively flame retarded with vinyl-type flame-retardant monomers containing both bromine and phosphorus atoms. Thermogravimetric analysis indicates that the decomposition temperature of flame-retardant monomer is more closely matched to the decomposition temperature of cured oligoester acrylate resin than to that of cured urethane acrylate resin. The efficiency of each flame-retardant monomer in oligoester acrylate resin is higher than in urethane acrylate resin by a factor of ∼ 2.2. The individual and the combined effects of tribromophenyl acrylate and triphenyl phosphate on the oxygen index of UV curable urethane acrylate resin have been studied. The bromine phosphorus synergistic action of the two flame-retardant components is evaluated quantitatively, and a maximum intermolecular bromine phosphorus synergism was observed in a flame-retarded formulation containing a Br/P atom ratio of 2. In the three acrylic monomers containing both bromine and phosphorus atoms, the optimum intramolecular bromine phosphorus synergism was observed at a monomer also containing a Br/P atom ratio of 2.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 0887-624X
    Keywords: polyphosphazene ; phosphoranimine ; phosphine azide ; phosphonite ; silyl azide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction between bis(2,2,2-trifluoroethyl) phenylphosphonite and trimethylsilyl azide at temperatures from 70 to 120°C provides a mixture of bis(2,2,2-trifluoroethoxy)phenylN-(trimethylsilyl) phosphoranimine and poly(phenyl-2,2,2-trifluoroethoxyphosphazene). The polymer is probably formed by phosphine azide intermediates because the phosphor-animine is thermally stable up to 200°C. The polyphosphazene is an amorphous stereo-random polymer with a glass transition temperature at -31°C.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 37
    ISSN: 0887-624X
    Keywords: photopolymerization ; photocalorimetry ; benzophenones ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A photocalorimetric study of butyl and lauryl acrylates (BA and LA) polymerization photoinitiated by several benzophenone derivatives is reported. Molecular weight measurements and end-chain group analysis of the samples are also described and the results are compared with those obtained by dilatometric technique. The role played by the long methylene chain in lauryl acrylate is discussed
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 38
    ISSN: 0887-624X
    Keywords: interpenetrating polymer networks ; poly(urethane carbonate) ; polyvinyl pyridine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simultaneous interpenetrating polymer networks (IPN's), pseudo IPN's, and liner blends of aliphatic poly(carbonate-urethane) (PCU) and polyvinyl pyridine (PVP) have been prepared and characterized by DSC, DMA, and TEM. The full IPN's of PCU and PVP had a single phase morphology only above 50 wt % PCU, as determined by both DSC and DMA and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PVP and in their linear blends there exist multiple glass transitions and melting points seen by DSC and DMA indicating phase incompatibility. The full IPN's exhibited superior ultimate mechanical properties and solvent resistance as compared to the pseudo IPN's, liner blends, and the pure crosslinked PCU and PVP networks.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 39
    ISSN: 0887-624X
    Keywords: PEEK ; reactive oligomer ; crosslinking ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino-terminated polyetheretherketone (PEEK) oligomers were prepared by the condensation of 4,4′-difluorobenzophenone and hydroquinone in the presence of a calculated excess of m-aminophenol endblocker. The molecular weight of the oligomer was controlled by the manipulation of the ratio of difluoride to hydroquinone with the appropriate stoichiometric amount of m-aminophenol ensuring amino termination. The thermally induced self-crosslinking of these oligomers was studied by differential scanning calorimetry (DSC). Curing was found to be quite slow, taking up to 1 h to reach completion at 668 K. Cured materials were all completely amorphous in contrast to the semi-crystalline starting material. The limiting Tg reached on curing was found to be proportional to the percentage of reactive terminal groups, as would be expected.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 40
    ISSN: 0887-624X
    Keywords: microsphere ; concentration effects ; growth mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of the monomer concentration were investigated on the preparation of diethylene glycol dimethacrylate (2G) microspheres by radiation-induced polymerization. The monomer concentration strongly affected the conversion and the shape of the microspheres. The particles were obtained in the range from 2 to 24 vol % of 2G monomer. The effective concentration for the preparation of monodisperse microspheres is around 10 vol %. Higher monomer concentrations up to 24 vol % gave rough surface particles. Considering the effects on the number of microspheres in the solution, the authors introduced the inhibiting region, where one microsphere disturbs the existence of another microsphere, and tried to explain the mechanism of the microsphere growth. The competition between the propagation and the crosslinking reactions is balanced to give the microspheres.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 41
    ISSN: 0887-624X
    Keywords: polyethers ; silyl method ; alkylation ; ionomers ; 15N-NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three poly(pyrazine-ether)s were prepared from 2,6-dichloropyrazine, silylated bisphenol-A and, in two cases, 4,4′-dichlorodiphenylsulfone. The alkylation of these poly(pyrazine-ether) with methyl triflate, dimethyl sulfate, methyl 4-nitrobenzenesulfonate, or γ-propanesultone was studied by 1H-NMR spectroscopy in nitrobenzene. Several N-methylated poly(pyrazine-ether)s were also isolated and characterized by elemental analyses, inherent viscosities, 1H-NMR spectra, 15N-NMR spectra, and DSC measurements. Furthermore, their solubilities in six different solvents were determined. Complete methylation raises the glass transition temperatures, reduces the solubility in aprotic solvents, and favors dissolution in methanol or ethanol.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: latex ; emulsion ; polymerization ; catalysis ; oxidation ; epoxidation ; porphyrin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three types of cationic polymer latexes were prepared by emulsion copolymerization of vinylbenzyl chloride, divinylbenzene and a third monomer, vinyl octadecyl ether, styrene, or n-decyl methacrylate, followed by quaternization with trimethylamine. The latexes had 44-71 nm diam and polydispersity indices of 1.06-1.10. Vinyl octadecyl ether did not copolymerize but hydrolyzed under the polymerization conditions to produce 1-octadecanol, which as a coemulsifier gave highly viscous latexes. The tetraanion 5,10,15,20-tetrakis-(2,6-dichloro-3-sulfonatophenyl) porphinatomanganese (III) chloride bound irreversibly to the cationic latexes and was an active catalyst for oxidations of alkenes by sodium hypochlorite and potassium peroxymonosulfate in the absence of added organic solvent. The porphyrin catalyst in the latexes was more active than in solution. Porphyrin catalysis gave epoxides concurrently with competing uncatalyzed hypochlorous acid oxidations to complex mixtures of allylic chlorides, allylic alcohols, α,β-unsaturated ketones, and chlorohydrins.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 0887-624X
    Keywords: ab initio ; AM1 ; cationic polymerization ; reaction mechanism ; furans ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: SCF ab initio and AM1 semiempirical calculations with full geometry optimization have been carried out to model the initial steps of alkenylfuran cationic polymerization. Semiempirical procedures have been used to model propagation steps. Proton affinities of the relevant neutral species as well as the heats of formation of probable dimers were calculated. The results allow the explanation of the experimental behavior. The capabilities of the employed methods to describe these type of processes is discussed. It is confirmed that competition between vinyl and ring site attacks is the most important feature in these systems. © 1992 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polystyrene ; photooxidation ; oxygen ; nitrous oxide ; ultraviolet ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Strips of polystyrene held in a flowing O2 or N2O atmosphere have been exposed to 240-600 nm radiation. The extent of photooxidation has been followed by x-ray photoelectron spectroscopy (XPS). Although N2O is a more reactive gas than O2, it produces a less oxidized polymer surface. This surprising observation can be correlated to the photochemistry occurring at the gas/polystyrene interface. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polyimide ; thermally stable polymer ; nitrogen linked diamines ; aromatic tetracarboxylic dianhydrides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two diamines, 2,5-bis (4-aminophenyl)-2,5-diazahexane and 1,4-bis (4-aminophenyl)-1,4-diazacyclohexane were chosen as components for polyimidizations because they have melting points that differ by nearly 200°C (66-67 and 229-230°C, respectively) and are relatives of p-nitro-N,N-dimethylaniline. The melting points of the model compounds (phthalic anhydride) do not differ by as much as those of the free amines [303-304 and 386°C (DSC), respectively]. Six polyimides were prepared by a two-step polycondensation of the diamines with pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] bis-1,3-isobenzofurandione. DSC thermograms failed to indicate any distinct transitions up to 450°C, however, the polyimide prepared from 2,5-bis (4-aminophenyl)-2,5-diazahexane and pyromellitic dianhydride shows a slight break in its DSC curve at 233°C.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 46
    ISSN: 0887-624X
    Keywords: ring-opening polymerization ; 1,1-disubstituted expoxides ; polyethers ; end groups ; deprotonation ; fluorinated epoxides ; aluminum catalysts ; DIBAL-O ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ring-opening polymerization of 1,2-epoxy-4,4,4-trifluoro-2-methylbutane (2) and its unfluorinated analogue, 1,2-epoxy-2-methylbutane (3), gives the expected polyethers when catalyzed by bis(diisobutylaluminum)oxide. However, the molecular weights are low because of a competing deprotonation/ring-opening of the epoxide that produces all three possible alkene end groups and their stereoisomers. With 2, deprotonation occurs mainly at the methyl group to give the terminal double bond and only minor amounts of the internal double bond. However, 3 gives the opposite regiochemistry. A model is proposed where this reaction occurs within an aluminum(polyether oxide) bound to the least hindered face of the epoxide ring. In this model, the different regiochemistries originate from a concerted and highly directed deprotonation/ring-opening of 2 versus a step-wise deprotonation of 3 through its ring-opened, tertiary-cation.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 47
    ISSN: 0887-624X
    Keywords: adsorption ; desorption ; association ; roto-fluorescence ; probe ; polystyrene ; glass-transition ; polymer transitions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fluorescence intensity and residual weight of poly(styrene-co-divinylbenzene) saturated with a 〈 0.003M solution of a intramolecular-rotor-fluorescent probe-molecule in a volatile liquid were monitored simultaneously as the system evaporated at 23°C to virtual dryness. The “breakpoints” in the pattern for fluorescence increase coincided with the “breakpoints” in the kinetics of desorption with respect to the number, αt of residual sorbed volatile molecules per phenyl group in the polymer, showing that both time-studies reflect the same physical changes in the system that occur reproducibly as αt decreases monotonically through α′s and α′g the compositions that signal respectively incipient elimination of volatile molecules immobilized by adsorption to polymer, and incipient transition of the system from the rubbery state to the glassy state. The fluorescence intensity attained its asymptotic limit before αt became equal to αg the composition identified earlier to be that which marks completion of the transition to the glassy state.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polyene polymers ; polyepoxide ; epoxidation reaction ; catalysis ; metalloporphyrins ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyene polymers [natural rubber (cis-polyisoprene), trans-polyisoprene, and cis-polybutadiene] were transformed to the corresponding polyepoxides which are a polyalcohol and soap precursor. The catalysts used were chloro- or acetato-manganese(III) tetraphenylporphyrin [MnIII(TPP)Cl or MnIII(TPP)OAc] in association with two different oxygen donors, sodium hypochloride and iodosylbenzene (Por, unspecified porphyrinato ligand; TPP, 5,10,15,20-tetraphenylporphyrinato ligand). This transformation in either biphasic system, H2O(aqua)-CH2Cl2 or PhIO(solid)-CH2Cl2, was monitored by 1H-NMR and IR spectroscopy. In both cases the transformation to the polyepoxide was completed within a few hours. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 49
    ISSN: 0887-624X
    Keywords: fluoropolymers ; low dielectric constant ; thermally stable ; aromatic polyethers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of fluorinated aromatic polyethers was synthesized via aromatic nucleophilic substitution of highly fluorinated aromatics (1,2,4,5-tetrafluorobenzene, hexafluorobenzene, and decafluorobiphenyl) with bisphenol AF or bisphenol A. Polymerization with 1,2,4,5-tetrafluorobenzene was not observed, and polymerization of hexafluorobenzene with bisphenol proceeded only if the potassium carbonate-bisphenol ratio was carefully controlled. The polymer condensed from decafluorobiphenyl and bisphenol AF was prepared in 77% yield with an inherent viscosity of 1.01 dL/g. The polymer prepared from the condensation of decafluorobiphenyl with bisphenol A was obtained in 48% yield with an inherent viscosity of 0.28 dL/g. These polymers were very soluble in common organic solvents, formed clear, colorless films, and were thermally stable (〉 450°C by TGA). The fully fluorinated polymer exhibited low water uptake (0.3%) and dielectric constant (2.17). © 1992 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 50
    ISSN: 0887-624X
    Keywords: liquid crystal ; photoactive polymer ; photo-Fries ; optical data storage ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of three methacrylate monomers with cinnamate ester side-chains and of a further monomer with a corresponding cinnamide side-chain are described. Two of the monomers, with isomeric structures, were thermotropic liquid crystals. Although the clearing points were very similar the crystal melting points differed by 8°C. One compound also exhibited a monotropic smectic phase, behavior not shown by its isomer. The other two monomers were not liquid crystalline. The monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with methyl methacrylate. In the case of one of the mesogenic ester monomers, copolymers with a cyanophenyl benzoate monomer were also prepared. Three of the four monomers formed thermotropic liquid crystalline homopolymers and the copolymers with the benzoate monomer were also liquid crystalline. The monomers were considered as photoactive components of polymeric liquid crystals. As a preliminary investigation of their photochemistry, copolymers with methyl methacrylate were prepared and irradiated in solution with a broad-band source. Under these conditions two of the materials show a facile photo-Fries rearrangement of the aryl cinnamate ester group. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 51
    ISSN: 0887-624X
    Keywords: gel ; display device ; electrochromism ; electrochromic device ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymer gel films [poly(1-vinyl-2-pyrrolidinone-co-N,N′-methylenebisacrylamide) (PVPD)] which contain simple organic electrochromics [p-diacetylbenzene (p-DAB), dimethyl- or diethyl terephthalate (p-DMP or p-DEP)] are prepared and their optical responses to applied voltage are investigated. p-DAP/PVPD film is colored in green by the application of 1.2 V vs. Pt wire (quasireference electrode) across the film, and p-DMP/PVPD and p-DEP/PVPD films are colored in red by the application of -2.5 and -1.5 V vs. Pt, respectively. Their coloring responses are about a few seconds and the bleaching process also occurs rapidly. The films have no optical memory effect. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 52
    ISSN: 0887-624X
    Keywords: saturated fluorocarbon ; plasma polymerization ; surface fluorination ; ESCA ; sputtering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The glow discharge of a series of saturated fluorocarbons, CnF2n+2 (n = 1, 2, 4, 6, and 8), was studied with glass substrates which do not contain any hydrogen. It was found that the deposition rate was a function of the F/C ratio of the starting fluorocarbons. That is, fluorocarbons with higher F/C ratio, such as CF4 and C2F6, hardly polymerized, while fluorocarbons with lower F/C ratio, such as C8F18, polymerized as well as C2F4. After plasma exposure, the surface of glass substrate was characterized by measurements of water contact angle, water droplet rolling-off angle, and ESCA. Although all saturated fluorocarbon plasmas could alter the surface more hydrophobic than before, the deposited materials from fluorocarbons with higher F/C were not stable. Also, in plasmas with high F/C fluorocarbons, i.e., CF4 and C2F6, sputtering of the electrode material was observed. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 53
    ISSN: 0887-624X
    Keywords: electrically conducting polymers ; 3,3′-dimethoxy-2,2′-bithiophene ; 3-methoxythiophene ; synthesis ; polymerization ; electrochemistry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new electroactive polymer, namely poly(3,3′-dimethoxy-2,2′-bithiophene) has been prepared by voltammetric polymerization of 3,3′-dimethoxy-2,2′-bithiophene. Due to a different coupling pattern (equivalent to “head-to-head,” and “tail-to-tail” coupled alkoxythiophene rings), poly(3,3′-dimethoxy-2,2′-bithiophene) exhibits different voltammetric properties than the corresponding “head-to-tail” coupled polymer, i.e., poly(3-methoxythiophene). Poly(3,3′-dimethoxy-2,2′-bithiophene) gives very sharp oxidation and reduction peaks indicating an abrupt insulator to conductor transition. This hypothesis was corroborated by the studies of relative resistance as a function of electrode potential. Sharper and better-defined redox peaks may indicate better stereoregularity of poly(3,3′-dimethoxy-2,2′-bithiophene) as compared to poly(3-methoxythiophene) since in this compound the 5,5′-coupling positions are geometrically equivalent and no coupling defects are expected. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 54
    ISSN: 0887-624X
    Keywords: adamantane polymers ; acetylene-terminated ; high temperature thermosets ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Diethynyl-5,7-dimethyladamantane, 1,3-diethynyl-5-phenyladamantane, 1,3,5-triethynyladamantane, and 3,3′-diethynyl-1,1′-biadamantane, were synthesized and polymerized thermally at 210°C. The thermoset resins obtained were post-cured at 300°C for 16 h to give materials that exhibited onsets of degradation (TGA) in air at 460-477°C and in helium at 460-485°C. The fully cured materials did not exhibit any detectable DSC transitions between 25 and 400°C. An attempt to thermally polymerize 1-ethynyl-3-phenyladamantane was unsuccessful. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 55
    ISSN: 0887-624X
    Keywords: Diels-Alder crosslinking ; polystyrene ; thermally reversible crosslinking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of maleimidomethylated polystyrene with difurfuryl adipate or with furfuryl alcohol-esterified poly[styrene-co-(maleic anhydride)] underwent thermally reversible Diels-Alder crosslinking. Reversal of crosslinking occurred rapidly at 150°C. The instability of the furfuryl group, however, limits the practicability of the reaction. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 56
    ISSN: 0887-624X
    Keywords: spiro(benzoxasilole) ; oxetane ; catalysis ; polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A spiro(benzoxasilole) catalyst, 3,3,3′,3′-tetrakis(trifluoromethyl)-1,1′-(3H,3H′)-spirobis(1,2-benzoxasilole) was used to polymerize 3,3-R,R′-oxetanes: BEMO (R, R′ = ethoxymethyl), AMMO (R = azidomethyl, R′ = methyl), NMMO (R = nitratomethyl, R′ = methyl), BAMO (R, R′ = azidomethyl), and BCMO (R, R′ = chloromethyl) with descending rates in this order. 31P-NMR of polymerization mixtures quenched using Bu3P are consistent with an oxonium ion propagating species. Water is not a cocatalyst because it increases the induction period which is not eliminated by the proton trap 2,6-di-t-bu-tylpyridine. The propagating chains were terminated by transfer with the ether oxygen of the polymer either intermolecularly or intramolecularly. The index of propagation to chain transfer, Kkikp/ktr, varies over more than three orders of magnitude for BEMO 〉 AMMO 〉 NMMO 〉 BAMO. However, kp/ktr for the four monomers differ by less than a factor of five indicating the same factors are affecting propagation and chain transfer. Addition of benzyl alcohol and propandiol produced poly(BEMO) having one and two hydroxyl termini, respectively. These telechelic polymers can be used to synthesize linear triblock or multiblock copolymers of oxetane derivatives. © 1992 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 57
    ISSN: 0887-624X
    Keywords: polymeric isocyanates ; polymeric crosslinkers ; nontoxic routes ; chloromethyl polystyrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The environmental regulations regarding the solvent emissions have given impetus to the formulation of powder coatings and high solids coatings which require oligomeric or polymeric crosslinkers of desired functionality. We are exploring nontoxic routes for the preparation of polymeric isocyanates and isocyanate precursors. In this article, we report nucleophilic displacement of polymer-bound alkyl halides by cyanate ion as a novel route to polymeric isocyanate crosslinkers with no intermediacy of either phosgene or low molecular weight isocyanates. The effects of solvent and phase-transfer catalyst on the selectivity of the reaction are discussed. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.