Correlation between Molecular Distance Variation and Thermal Volume Expansion in Amorphous Polymers using WAXS
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In this study, we investigate the thermal expansion characteristics of amorphous polymers based on molecular distance information obtained from Wide-angle X-ray scattering (WAXS). Halo-type scattering patterns were identified for polystyrene and poly(methyl methacrylate), which are representative amorphous polymers. Considering chemical structures of the polymers, inner- and outer-halo patterns are associated with inter- and intra-molecular interaction, respectively. During in-situ WAXS experiments with heating, the temperature with rapid changes in inter- and intra-molecular distance suggest the glass transition temperature of the polymers. Assuming that amorphous polymer chains are tube-like chains, furthermore, the variations of inter- and intra-molecular distance enable to evaluate thermal expansion coefficients that are consistent with those obtained by spectroscopic ellipsometry measurements.