摘要:

AbstractPolyesters have been synthesized by polycondensation of terephthaloyl dichloride or isophthaloyl dichloride with hindered biphenols and hydroquinones which contain bulky substituents (methyl and phenyl) on the arylene ring. Polymers derived from isophthaloyl dichloride have better solubility and lower glass transition temperatures than the corresponding polymers obtained from terephthaloyl dichloride. © 1994 John Wiley&Sons, Inc

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320111

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractElectrochemical synthesis of polyaniline (PANI) was carried out under cyclovoltammetric conditions using H2SO4, HCl, HNO3, and HClO4as supporting electrolytes. The observed different rate of PANI deposit growth depending on the acid in the solution has been explained on the grounds of a different degree of specific adsorption for particular anion. It has been found that morphology of the deposit depends greatly upon the anion present in the solution. Thus, PANI synthesized from the solution of oxyacids results in a dense sponge‐like structure while PANI from the hydrochloric acid solution results in a spaghetti‐like structure. The structure of the deposit influences the conductivity, being higher for a dense deposit from oxyacid solutions and three orders of magnitude lower in case of a deposit from hydrochloric acid solution. © 1994 John Wiley&Sons,

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320112

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe kinetics of formation of polyurethane prepolymers is studied by an analytical technique which involves reactive quenching of the isocyanate, separation of the oligomeric species by GPC, and measurement by UV absorbance of the quenched moieties. The precision of the kinetic parameters and the ratios of the oligomers are determined. The effect of changes in reactant stoichiometry on the ratio of oligomers is measured and compared to the value predicted by an equation from Flory. Toluene diisocyanate is shown to give fewer high oligomers than predicted, while methylene diphenylene diisocyanate gives nearly the predicted values. Tetramethylxylene diisocyanate gives more high oligomers than predicted, an unexpected but possibly important result. Catalyst is shown to increase the reaction rate of the last by more than 200 times. © 1994 John Wiley&Sons, Inc

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320113

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThin films have been deposited from radio‐frequency glow discharges fed with vapors of a silicon‐ and fluorine‐containing organic compound, namely 2,4,6‐tris[(3,3,3‐trifluoropropyl) (methyl)] cyclotrisiloxane, in mixture with argon.2,4,6‐tris[(3,3,3‐trifluoropropyl)(methyl)]cyclotrisiloxaneAtriodereactor has been utilized to deposit films by independently changing substrate temperature and bias‐induced ion‐bombardment. Laser interferometry, electron spectroscopy for chemical analysis and Fourier‐transform infrared spectroscopy have been used to monitor film growth rate and composition. Results unambiguously show an activating effect of the ion‐bombardment, which confirm the validity of the ion‐assisted deposition model utilized for the plasma deposition of both teflon‐ and silicone‐like films. In our experiments, low substrate temperature and bias conditions results in films with a “monomer‐like” stoichiometry, while drastic conditions give origin to materials with a completely different composition and a markedly increased hard

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320114

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractHigh molecular weight polymers containing oligosiloxanes in the backbone were made by the reaction of aromatic diols with α,ω‐diaminosiloxane homologs. The glass transition temperatures dropped by 30–40°C in a homologous series with each siloxane added. The thermal stability also suffered when increasing the number of siloxane groups. The polymers all displayed high % char measurements and one polymer (disiloxane) tested had aV0rating by UL‐94 testing. The trisiloxane‐containing polymer had a high percent elongation at break (>300%). All the polymers tested were fairly susceptible to hydrolysis. © 1994 John Wile

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320115

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractMultifunctional monomers (trimethylol propane trimethacrylate, trimethylol propane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol monohydroxy pentaacrylate) were photopolymerized with 2,2‐dimethoxy‐2‐phenylacetophenone as the photoinitiator to produce highly crosslinked networks. The volume shrinkage behavior and the reaction kinetics were studied under various reaction conditions. The volume shrinkage and maximum functional group conversion were dependent on the number of functional groups, type of functional group, and the curing conditions. The maximum functional group conversion was also dependent on the reaction temperature. All the polymerized systems exhibited a strong coupling between the volume relaxation and the reaction kinetics. The kinetic constants were also determined as a function of conversion, and the termination mechanism was found to be reaction diffusion dominated even at low conversions. The importance of these results on the prediction of the reaction behavior for multifunctional monomers producing highly crosslinked polymers is discussed. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320116

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA new silolene‐bridged compound, racemic (1,4‐butanediyl) silylene‐bis (1‐η5‐in‐denyl) dichlorozirconium (1) was synthesized by reacting ZrCl4with C4H8Si (IndLi)2in THF.1was reacted with trialkylaluminum and then with triphenylcarbenium tetrakis (penta‐fluorophenyl) borate (2) to producein situthe zirconocenium ion (1+). This “constraint geometry” catalyst is exceedingly stereoselective for propylene polymerization at low temperature (Tp= −55°C), producing refluxingn‐heptane insoluble isotactic poly(propylene) (i‐PP) with a yield of 99.4%, Tm= 164.3°C, δHf= 20.22 cal/g and M̄w= 350 000. It has catalytic activities of 107−108g PP/(mol Zr · [C3H6] · h) in propylene polymerization at the Tpranging from −55°C to 70°C, and 108polymer/(mol Zr · [monomer] · h) in ethylene polymerization. The stereospecificity of1+decreases gradually as Tpapproaches 20°C. At higher temperatures the catalytic species rapidly loses stereochemical control. Under all experimental conditions1+is more stereospecific than the analogous cation derived fromrac‐dimethylsilylenebis (1‐η5‐indenyl)dichlorozirconium (4). The variations of polymerization activities in ethylene and in propylene for Tpfrom −55°C to +70°C indicates a Michaelis Mention kinetics. The zirconocenium‐propylene π‐complex has a larger insertion rate constant but lower thermal stability than the corresponding ethylene π‐complex. This catalyst copolymerizes ethylene and propylene with reactivity ratios of comparable magnituderE˜ 4rp. Furthermore,rE.rp˜ 0.5 indicating random copolymer formation. Both1and4activated with methylaluminoxane (MAO) exhibit much slower polymerization rates, and, under certain conditions, a lower stereo‐selectivity t

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320117

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

Abstract6‐Hydroxythioxanthone‐2‐carboxylic acid (HTCA) was prepared from commercial dimethylnitroterephthalate via 2‐(4'‐hydroxythiophenyl) terephthalic acid. HTCA was acetylated and polycondensed in an inert reaction medium at 350 or 400°C. An insoluble and infusible, highly crystalline polyester was obtained, which did not form whisker‐like crystals. Furthermore, copolyesters with 4‐hydroxybenzoic acid (4‐HBA) were synthesized and whiskers were obtained at a molar ratio of 1 : 9 (in favor of 4‐HBA). A meltable, nematic copolyester was prepared by cocondensation of silylated 6‐acetoxythioxanthone‐2‐carboxylic acid and silylated 4‐acetoxybenzoic acid in bulk.

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320118

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolyimide/polyimide molecular composite (MC) films comprised of a rigid polyimide derived from biphenyltetracarboxylic dianhydride (BPDA) andp‐phenylenediamine (PDA) and a flexible polyimide derived from BPDA and bis (3,3'‐diaminodiphenyl) acetylene (intA) and/or oxydianiline (ODA) were prepared by blending the polyamic acid solutions in 7 : 3 weight ratio, and then imidizing the blend films. Acetylene content in the flexible polyimide backbone was controlled by the ratio of intA and ODA. Cold‐drawing of the blend polyamic acid films, followed by imidization, gives high modulus polyimide/polyimide MC films. The modulus of the MC films increased almost linearly with the draw ratio, reaching 25.5 GPa for the 40% drawn film. Acetylene groups in the flexible polyimide can be thermally cured to crosslink. The onset of exotherm appeared at 340°C on DSC, reaching maximum at 398°C. After the thermal crosslinking, the MC films maintained the high modulus, though elongation became small. Taking advantage of the crosslinkable acetylene units, two MC films were laminated and processed at 400°C for 20 min under 100 kg/cm2to give a good‐quality laminate film. The interface of the two films was strongly bonded through the crosslinking of acetylene groups. Laminate films maintained the high modulus afforded by the cold‐drawing. © 1994 John Wi

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320119

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320120

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY