Opposing Effects of Side-Chain Flexibility and Hydrogen Bonding on the Thermal, Mechanical, and Rheological Properties of Supramolecularly Cross-Linked Polyesters
Opposing Effects of Side-Chain Flexibility and Hydrogen Bonding on the Thermal, Mechanical, and Rheological Properties of Supramolecularly Cross-Linked Polyesters
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侧链柔性和氢键对超分子交联聚酯的热、机械和流变特性的相反影响
DOI：
10.1021/acs.macromol.8b01781
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发表时间：
2018-11-27
期刊：
影响因子：
5.5
通讯作者：
Joy, Abraham
中科院分区：
文献类型：
--
作者：
Liu, Qianhui;Wang, Chao;Joy, Abraham
我们报道了一系列含有垂坠仲酰胺基团的聚酯的设计，以探索氢键和链柔韧性对其热、机械和流变性能的累积效应。关于含仲酰胺基团聚合物的研究通常集中在氢键相互作用对其机械、自组装或自修复性能的影响上，而链柔韧性的影响往往被忽视。为了探索氢键和链柔韧性的累积效应，在这项工作中，聚酯被设计成具有一个或两个垂坠的仲酰胺丙基，并与具有一个垂坠的酯丙基的对照聚酯进行比较。结果表明，氢键作用提高了玻璃化转变温度（T-g）、杨氏模量和聚合物脆性。但在较高温度下（T-g + 50℃），流变学表明，含两个酰胺基团的聚酯具有最短的链弛豫时间和最低的零剪切速率粘度（eta(0)）。这些结果是违反直觉的，因为有两个氢键酰胺基团的聚合物弛豫速度更慢，粘度更高。我们的研究结果表明，侧链柔韧性和氢键相互作用的相反影响可以用作设计具有所需流变性能的材料的策略。
We report the design of a series of polyesters containing pendant secondary amide groups to probe the cumulative effects of hydrogen bonding and chain flexibility on their thermal, mechanical, and rheological properties. Reported studies on polymers with secondary amide groups have usually focused on the effect of hydrogen bonding interactions on the mechanical, self-assembly, or self-healing properties, whereas the effect of chain flexibility has often been overlooked. In an effort to probe the cumulative effects of hydrogen bonding and chain flexibility, in this work polyesters were designed with either one or two pendant secondary amide-propyl groups and compared to a control polyester with one pendant ester-propyl group. The results show that hydrogen bonding increases glass transition temperature (T-g), Youngs modulus, and polymer brittleness. But at higher temperature (T-g + 50 degrees C), rheometry shows that the polyester containing two amide groups has the shortest chain relaxation time and the lowest zero-shear rate viscosity (eta(0)). These results are counterintuitive, since the polymer with two hydrogen bonding amide groups was expected to relax more slowly and have higher viscosity. Our results demonstrate the opposing effects of side-chain flexibility and hydrogen bonding interactions can be used as a strategy to design materials with desired rheological properties.