摘要:

AbstractAs in the case of reinforcing filler‐induced increase in hysteresis in rubbers, placement of aluminum (A1) foil to the surface of a rubber blend of epichlorohydrin rubber and carboxylated nitrile base induces increased hysteresis of the rubber due to adhesion between Al and the rubber blend. Changes in hysteresis loss due to Al foil can be correlated with the peel strength of Al‐rubber‐Al joints. © 1995 John Wiley&Son

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331601

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractEPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on silica has been used to characterize the conformation and local dynamics of the chains. Grafted molecules of MW 2000 with grafting ratios of 0.045, 0.057, 0.126, and 0.42 molecules/nm2were in contact with benzene. The mobility of the label was compared with that observed for solution of PEO from very diluted to highly concentrated and even bulk PEO. Thus, the concentration inside the grafted layer could be evaluated and also the thickness, which evolves rather linearly with the grafting ratio. © 1995 John Wiley&Sons, Inc

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331602

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractPolythiophene films have been deposited on a platinum electrode surface by direct oxidation of thiophene in BF3‐ethyl ether solution containing a controlled amount of water (5 mM). The electric and mechanical properties of the films were studied. Experimental results demonstrated that the films prepared at low applied potentials were semiconductors with conductivities in the order of 10−1s cm−1. The strengths of these films were high and comparable to those of some widely used engineering plastics such as poly(propylene) and poly(vinyl acetate). The conductivities of the PT films varied with the value of applied potential used for electrolysis and passed through a maximum of 19.13 s cm−1at +1.6 V. At a given applied potential, low experimental temperature, and monomer concentration led to formation of films with high quality. © 1995 John Wiley&S

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331603

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe electric field‐induced dynamic phase‐matching of second harmonic generation (SHG) waveguide was demonstrated by using a main chain polyarylamine. The linear and nonlinear optical properties of this polymer are presented. The optimum phase‐matching thickness was controlled by applying an electric field to the polymer waveguide. The effective phase‐matching thickness variation induced by poling is about 0.025 μm that is six times larger than full width at the half‐maximum (FWHM) of phase‐matching thickness in conventional slab waveguide. The efficient phase‐matched SHG was observed from a taperless slab wave‐guide. The optical loss of poled polymer on glass substrate at 632.8 nm was 2.7 dB/cm. © 1995 Joh

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331604

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe13C NMR spin‐lattice relaxation times (T1) of anhydroglucose units vary with the number of substituents, and theT1values of unsubstituted anhydroglucose units ofO‐carboxymethylcellulose are longer than those of amylose. Those results indicate that in water, the rotational motions of anhydroglucose units of cellulose derivative are quite important local motions contributing to the13C NMR spin‐lattice relaxation, and within a cellulose chain, anhydroglucose units rotate with different degrees of freedom depending on their environment. Moreover, the13C NMR spin‐lattice relaxation data indicate that the mobilities of ionic substituents are dependent on substitution positions as well as their ionic interaction. © 1995 John Wiley&S

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331605

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractPolarized fluorescence spectroscopy is used to investigate the photophysical behavior of poly(p‐phenylphenylenevinylene) (PPPV) in polystyrene matrix in comparison with oligomeric model compounds. For this purpose PPPV is modeled by a chain consisting of a distribution of independent oligomeric segments. Excitation energy transfer (EET) between the segments depends on the wavelength of excitation, not only for transfer along an isolated polymer chain, but also for intermolecular transfer at high concentration of PPPV. The spatial range of EET, as indicated by fluorescence depolarization, is reduced for excitation at the long wavelength edge of the absorption spectrum (“red‐edge‐effect”). © 1995 John Wiley

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331606

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractIntrinsic viscosity, [η], weight‐average molecular weight,Mw, relationships are reported for narrow molecular weight distribution linear polyisoprene and polystyrene samples in CCl4at 25°C. Molecular weight values cover a range nearly two orders in magnitude, extending as low as 3 × 103. In the case of polystyrene there exists a molecular weight range (aroundMw= 16,700) corresponding to a change in the Mark‐Houwink‐Sakurada (MHS) exponent from α = 0.71 to α = 0.54. Comparisons between the viscometric and hydrodynamic radii, from literature data, are made. For polyisoprene the MHS relationship is reported in CCl4, for the first time. For this case α = 0.713 for the whole range of molecular weights studied. Values for the second virial coefficient from low‐angle light‐scattering measurements support the conclusions drawn from viscometry that CCl4is a good solvent for both polymers studied. The different behavior of the MHS exponent may be attributed to the difference in chain flexibility. © 1995 John

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331607

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry (DSC) has been applied to characterize the glass transition behavior of the blends formed by bisphenol‐A polycarbonate (PC) with a tetrafunctional epoxy (tetraglycidyl‐4,4′‐diaminodiphenyl methane, TGDDM) cured with 4,4′‐diaminodiphenylsulphone (DDS). A rare miscibility in the complete composition range has been demonstrated in these blends. Additionally, the blend morphology was examined using scanning electron microscopy (SEM) and a homogeneous single‐phase PC/epoxy network has been observed in the blends of all compositions. Moreover, polycarbonate incorporation has been found to exert a distinct effect on the cure behavior of the epoxy blends. The cure reaction rates for the epoxy‐PC blends were significantly higher due to the presence of PC. In addition, the cure mechanism of the epoxy blends was no longer autocatalytic. Ann‐th order reaction mechanism withn= 1.2 to 1.5 has been observed for the blends of DDS‐cured epoxy with PC of various compositions studied using DSC. The proposedn‐th order kinetic model has been found to describe well the cure behavior of the epoxy/PC blends up to the vitrification point. © 199

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331608

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this work we compare four dielectric relaxation models that explicitly include the viscoelastic properties of the environment to define the dielectric relaxation process. These models are the Debye, Gamant, DiMarzio‐Bishop, and the Havriliak‐Havriliak models. Debye's model assumes a Newtonian viscosity and solves the hydrodynamic problem exactly leading to the venerable Debye function. Gamant's used heuristic arguments to include a time‐dependent viscosity. These results lead to a splitting of the relaxation process. DiMarzio‐Bishop solved the hydrodynamic equations which included a time‐dependent viscosity exactly and applied the results to poly(n‐octyl methacrylate). The Havriliak‐Havriliak approach is based on statistical mechanics arguments that take into account strain energy which is associated with the polarization process. This model also requires a knowledge of the viscoelastic properties of the system. The results of the four models are compared. © 1995 John W

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331609

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dielectric behavior of an epoxide/ethylenediamine formulation has been studied during cross‐linking in the frequency range 103−1010Hz at 25°C and 70°C. Dielectric data were collected both in the frequency and in the time domains and analyzed in terms of a combination of two Havriliak‐Negami functions. A complete description of the evolution of the relaxation parameters during the reaction was obtained. The nature of the information yielded by dielectrometry on the dynamics of the system is discussed. © 1995 John Wiley&S

ISSN:0887-6266    

DOI:10.1002/polb.1995.090331610

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY