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Transparency of Temperature-responsive Shape-memory Gels Tuned by a Competition between Crystallization and Glass Transition
Chinese Journal of Polymer Science ( IF 4.1 ) Pub Date : 2020-07-09 , DOI: 10.1007/s10118-020-2456-0
You-Hao Wang , Jin Gong , Wen-Bing Hu

Transparency is often an important property in the practical applications of temperature-responsive shape-memory gels. We investigated the mechanism of significant transparency improvement upon a change in two copolymer gels with their molar ratios between stearyl acrylate and N, N-dimethylacrylamide from 1:1 to 0.75:1. By means of Flash DSC measurement, we made the thermal analysis characterization of crystallization and glass transition in two copolymer gels and compared the results to the parallel experiments of corresponding homopolymers. The results showed that the slightly lower content of stearyl acrylate sequences suppresses crystallization in their side chains due to the chemical confinement of comonomers on copolymer crystallization; meanwhile it shifts up the glass transition temperature of the backbone N, N-dimethylacrylamide sequences. Eventually on cooling, crystallization gives its priority position to glass transition in copolymer gels, resulting in a higher transparency of the gel without losing the shape-memory performance. To confirm the chemical confinement, we further compared the isothermal crystallization kinetics of stearyl acrylate side chains in the copolymer gel to that of their homopolymer. Our observations facilitate the rational design of the temperature-responsive shape-memory gels for the transparency property.



中文翻译:

通过结晶和玻璃化转变之间的竞争而调节的温度响应型形状记忆凝胶的透明度

在温度响应型形状记忆凝胶的实际应用中,透明度通常是重要的属性。我们研究了两种共聚物凝胶的变化(其硬脂酸酯丙烯酸酯与N,N之间的摩尔比不同)后透明性显着提高的机理。-二甲基丙烯酰胺从1∶1到0.75∶1。通过Flash DSC测量,我们对两种共聚物凝胶的结晶和玻璃化转变进行了热分析表征,并将结果与​​相应均聚物的平行实验进行了比较。结果表明,由于共聚单体在共聚物结晶过程中的化学作用,丙烯酸十八烷基酯含量稍低的含量会抑制其侧链的结晶。同时它提高了主链N,N的玻璃化转变温度-二甲基丙烯酰胺序列。最终在冷却时,结晶作用使其在共聚物凝胶中的玻璃化转变处于优先位置,从而在不损失形状记忆性能的情况下提高了凝胶的透明度。为了证实化学限制,我们进一步比较了共聚物凝胶中丙烯酸硬脂基丙烯酸酯侧链与其均聚物的等温结晶动力学。我们的观察有助于对温度响应型形状记忆凝胶进行透明性的合理设计。

更新日期:2020-07-10
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