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Simultaneous measurements of Raman spectroscopy and synchrotron two-dimensional (2D) wide-angle x-ray diffraction (WAXD) have been successfully demonstrated for in situ study of an anisotropic system: isotactic polypropylene (iPP) fiber under tensile deformation. A fiber-optic probe was used to remotely deliver the incident laser beam on the sample as well as to collect the Raman signal based on the confocal arrangement, whereas high resolution 2D WAXD patterns were obtained simultaneously at the same position during deformation of polymers. The combined techniques yielded complementary information on the molecular structural evolution in both crystalline and amorphous phases. 2D WAXD results showed that the α-form iPP crystals were converted into the mesophase upon stretching at room temperature. Corresponding Raman spectra showed that characteristic bands from the crystal phase became weaker or disappeared during the transition from the crystal phase to the mesophase. However, the bands associated with the helical structure were still present, indicating the remainder of the helical conformation in the mesomorphic phase. The persistence of the Raman band at 812 cm[sup -1] in the mesophase implied that the structural difference between the crystal phase and the mesophase in iPP is due to the packing defects, rather than the conformational deviations from the (...TGTG...) sequence in chains. The variations in the Raman intensity ratio (I812/I843) indicated that the overall orientation of the fiber increased during stretching. The demonstrated techniques will be particularly useful for in situ studies of anisotropic polymers, where orientational dependent structural information from both crystalline and amorphous phases needs to be collected simultaneously. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Structure evolution during deformation of unfilled natural rubber (NR) vulcanizate and filled ones with carbon black or calcium carbonate was investigated by the synchrotron x-ray diffraction. The crystallization onset strain, α0, was found to decrease by the inclusion of the filler. However, corrected α0 values into the effective strain ratio of deformable rubber portion were almost constant between filled and unfilled samples. Accordingly, our model of strain-induced crystallization of unfilled NR vulcanizates, assuming that melting temperature is independent of network-chain length (n), was applied to the filled samples. The discrepancy between classical theories and experimental results was thought to come from the distribution of n. By the inclusion of filler, the lateral crystallite size was decreased but the orientational fluctuation increased. The lattice of the strain-induced crystallites changed almost linearly with the nominal stress. In addition, the degree of lattice deformation decreased with the filler content, especially in the carbon black-filled system. All these experimental results are consistent with the proposed model. [ABSTRACT FROM AUTHOR]