由于多素的拓约束而导致的长期玻璃过渡
Kazuaki Kato1,2, Akihiro Ohara1, Hideaki Yokoyama1
1Department of Advanced Materials Science, Graduate School of Frontier Sciences , The University of Tokyo , 5-1-5 Kashiwanoha , Kashiwa , Chiba 277-8561 , Japan.
Journal of the American Chemical Society
|August 2, 2019
概括
聚素的拓约束影响了玻璃过渡的动态. 增加环覆盖延长了机械放松,表明部分运动超出了玻璃过渡温度 (Tg).
科学领域:
- 聚合物科学
- 材料科学
- 物理化学
背景情况:
- 多聚素是具有独特拓结构的高分子聚合物.
- 玻璃过渡 (Tg) 是影响聚合物动态和材料性能的关键性质.
- 对于设计先进材料来说,了解聚素中的Tg是必不可少的.
研究的目的:
- 调查拓约束对聚素玻璃过渡动态的影响.
- 系统地研究不同程度的环覆盖如何影响放松行为.
- 阐明分子运动与拓约束之间的关系.
主要方法:
- 用不同比例的聚合物和螺纹环分子合成的聚素.
- 差异热分析 (DTA) 用于确定玻璃过渡温度 (Tg).
- 机械放松测量以分析动态行为.
主要成果:
- 通过DTA观察到不同覆盖范围的多素具有类似的Tg值.
- 机械放松时间随着环覆盖率的提高而显著增加.
- 一个两步的放松过程出现了,其中一个依赖于覆盖范围的缓慢组件.
- 发现分段运动在高于Tg的温度下结,随着覆盖范围的增加而增加.
结论:
- 聚素的拓约束显著改变了玻璃过渡的动态.
- 虽然环从Tg的常规相互作用中释放出来,但它们的合作转换运动受到线程聚合物的阻碍.
- 越来越多的环覆盖带来了更高温度的细分运动,影响了材料的特性.
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