We investigated the thermal expansion of amorphous polystyrene (PS) and poly(methyl methacrylate) (PMMA) homopolymers using the temperature dependence of spatial electron-density correlations. The strong and broad X-ray interference maxima arising from inter- and intramolecular correlation distances were distinct, maintaining their shape during the heating of the samples to 250 °C. Three maxima characteristic of electron density correlations between the backbones, substituents along the chain, and repeat-units were observed. A remarkable temperature dependence was identified in the largest correlation distances arising from the intermolecular interactions. Based on the temperature dependence of the correlation distances, the coefficients of molecular expansion were very close to the coefficients of thermal expansion. This study provides a simple yet accurate way to correlate macroscopic volume expansions with the molecular expansion obtained from wide-angle X-ray scattering (WAXS) data.

中文翻译：

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深入了解无定形聚合物的热膨胀


我们利用空间电子密度相关性的温度依赖性研究了无定形聚苯乙烯 （PS） 和聚甲基丙烯酸甲酯 （PMMA） 均聚物的热膨胀。由分子间和分子内相关距离引起的强而宽的 X 射线干涉最大值是不同的，在样品加热到 250 °C 期间保持其形状。 观察到主链、沿链的取代基和重复单元之间的电子密度相关性的三个最大值特征。在分子间相互作用产生的最大相关距离中发现了显着的温度依赖性。基于相关距离的温度依赖性，分子膨胀系数非常接近热膨胀系数。本研究提供了一种简单而准确的方法，可以将宏观体积膨胀与从广角 X 射线散射 （WAXS） 数据获得的分子膨胀相关联。