摘要:

AbstractThe application of Raman spectroscopy to polymers and polymerization processes is surveyed and the advent of recent advances in instrumental techniques to polymer analysis is highlighted. Some of the problems of the more widely‐used infrared spectroscopic methods, for example in microstructural analysis of polydienes and copolymers, are discussed and the advantages of the Raman spectroscopic technique are explained. The use of near‐infrared excitation and Fourier‐transform Raman instrumentation for process monitoring and polymer composite studies is discussed. Raman microscopic and waveguide spectroscopic studies of small samples and polymer coatings on substrates are considered. Other applications are mentioned in the areas of polymer orientation, surface‐enhanced Raman scattering, conducting polymers, biopolymers and time‐resolve

ISSN:0377-0486    

DOI:10.1002/jrs.1250240803

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractNew classes of polymers and oligomers whose backbone consists of a network of delocalized π electrons have recently been synthesized and show electrical and non‐linear optical properties of great interest for new technologies. The vibrational spectra of these materials show peculiar features which, if properly interpreted, can provide unique structural information. The interpretation of the spectra requires the development of new theoretical tools. The theoretical and experimental aspects of the problem are presented. It is also shown that the nuclear relaxation following the excitation of the electrons by an intense electromagnetic field can be described in terms of the vibrational modes and can be related to the nuclear contributions to the non‐linear optical responses of the material. In this case Raman intensities play a determining

ISSN:0377-0486    

DOI:10.1002/jrs.1250240804

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe preparation and vibrational spectroscopic characterization of the hitherto unreported products of the copolymerization of 2,3‐dimethylbutadiene and methyl methacrylate are presented. The polymers were prepared by free radical polymerization using α,α′‐azobisisobutyronitrile as the initiator. Raman and Fourier transform infrared spectroscopic information on the 2,3‐dimethylbutadiene–methyl methacrylate copolymer is presented for a range of copolymers differing in the 2,3‐dimethylbutadiene to methyl methacrylate ratio. Quantitative information of the microstructure of the polymer and copolymer using the CC stretching vibrations is provided by Raman spectroscopy. Evidence is presented for the splitting of the CO stretching vibration, ascribed to aggregated syndiotactic and unaggregated syndio‐ and isotactic poly(methyl methacrylate) at 1734 and 1724

ISSN:0377-0486    

DOI:10.1002/jrs.1250240805

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPolarized Raman spectroscopy was used to determine the order parameters of the orientational distribution function for a series of stretched polyethylene foils with a relatively low degree of molecular orientational order. By combining measurements of the foil under stduy and of an isotropic polyethylene foil, simple backscattering experiments are sufficient to determine the orientation order parameters of the foil with molecular orientation. Practical considerations for obtaining polarized Raman spectra are discussed. The results are in good agreement with the order parameters obtained by IR dichroism and wide‐angle x‐ray diffraction. Differences between the various methods are discussed. The Raman method proves to be a relatively rapid method for obtaining information concerning the molecular orientation in polyethylene fi

ISSN:0377-0486    

DOI:10.1002/jrs.1250240806

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Raman waveguide spectra of a series of polymer laminates obtained using a simple optical waveguide coupling device are reported. The optical properties of these polymer films were obtained by measuring the waveguide coupling angles and the resulting electric field calculations were shown to predict (semiquantitatively) the observed spectra as a function of waveguide mode number. A discussion of the practical difficulties encountered with available polymer samples emphasizes why such measurements are not yet to be regarded as ‘routine’. No unequivocal evidence could be found for interfacial effects at the polymer/polymer interf

ISSN:0377-0486    

DOI:10.1002/jrs.1250240807

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractRaman spectra of poly‐4‐vinylpyridinium anion‐exchange membranes, immersed in aqueous solutions, were recorded. Assignments of some specific vibrational bands are proposed, allowing intensity measurements of appropriate signals versus pH or time. Membranes with low intrinsic pKvalues were analysed and the results were in agreement with those obtained by other techniques. Deprotonation kinetic data were obtained in relation to the reduced proton leakage of these mate

ISSN:0377-0486    

DOI:10.1002/jrs.1250240808

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractRaman spectroscopy was employed to study the polymerization of pyrrole over a selection of copper‐exhanged ZSM‐5 zeolites. No polymerization occurred on catalysts of low copper content, which suggested that a critical concentration of copper(II) cations was required for reaction. On ZSM‐5 materials with low Si/Al ratios, bands were detected which were characteristic of partially oxidized polypyrrole and monomeric pyrrole. The polymer was degraded in the presence of residual oxygen. It was shown that the polymer incorporated both aromatic‐ and quinoidal‐type structures. Further, resonance Raman spectroscopy suggested that the charge carrier present in the oxidized polymer was associated with the quinoid ar

ISSN:0377-0486    

DOI:10.1002/jrs.1250240809

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPolarized Raman spectra in the low‐frequency region were measured for single‐layered (Mon) and double‐layered (Orth II) polytypes of stearic acid, E form. In E(Mon) three intense bands due to the longitudinal acoustic modes (LAM) were observed in both the (cc) and (bc) polarizations (which is consistent with the crystal structure), whereas in E(Orth II) the (cc) and (bc) components split at different frequencies. The LAM modes were analysed using a simple coupled oscillator model involving an interaction between the terminal methyls. The LAM modes vibrating in‐phase between successive bimolecular layers appear at higher frequencies than the antiphase modes, because the interlayer interaction acts only on the former modes. The half‐widths of the higher order harmonics of LAM bands are about twice that of the fu

ISSN:0377-0486    

DOI:10.1002/jrs.1250240810

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn order to make vibrational assignments of the metastable orthorhombic modification of polyoxymethylene (o‐POM), polarized Raman and infrared spectra of a single crystal of deca(oxymethylene) diacetate, CH3COO(CH2O)10COCH3(POMAc10), a linear oligomer of POM, were measured and compared with previous results obtained using a micron‐sized single crystal of o‐POM. On the basis of the orientation of the o‐POM sublattice in the POMAc10 crystal, assignments of the zone‐centre modes of o‐POM was established and the unit cell orientation in the micron‐sized o‐POM single crystal was decided. The morphology‐dependent frequency shifts of the parallel infrared bands (B1modes) in the POMAc10 crystal, which has a specific morphological structure different from the lamellar crystal of high‐molecular‐weight o‐POM, were investigated on the basis of the transition

ISSN:0377-0486    

DOI:10.1002/jrs.1250240811

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIt is demonstrated that Raman spectroscopy can be used to study both the deformation micromechanics of high‐performance aramid polymer fibres and of these fibres in model, single‐fibre epoxy resin matrix composites. It is shown that the peak position of the 1610 cm−1aramid Raman band shifts to lower frequency under the action of tensile stress or strain due to the macroscopic deformation leading to direct stretching of the polymer molecules. These strain‐induced band shifts can be used to map the distribution of stress or strain along a discontinuous, aramid fibre inside an epoxy resin matrix from which the interfacial shear stress can be calculated. It is shown that the behaviour is consistent with that predicted by the classical shear‐lag analysis. The technique was also used to study the fragmentation process for an aramid fibre in an epoxy resin matrix in which the matrix strain exceeds the failure strain of the fibre. It is further demonstrated that the technique can be used to compare the interfacial properties of aramid fibres where the interfacial shear stress is found to be higher for sized fibres than for those which have been

ISSN:0377-0486    

DOI:10.1002/jrs.1250240812

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY