Lee Yoojin, Choi Subi, Kang Beom-Goo, Ahn Suk-Kyun
Department of Polymer Science and Engineering, Pusan National University, Busan 46241, Korea.
Department of Chemical Engineering, Soongsil University, Seoul 06978, Korea.
Materials (Basel). 2020 Jul 10;13(14):3094. doi: 10.3390/ma13143094.
Among the various types of shape changing materials, liquid crystal elastomers (LCEs) have received significant attention as they can undergo programmed and reversible shape transformations. The molecular engineering of LCEs is the key to manipulating their phase transition, mechanical properties, and actuation performance. In this work, LCEs containing three different types of butyl groups (n-, iso-, and sec-butyl) in the side chain were synthesized, and the effect of isomeric amine chain extenders on the thermal, mechanical, and actuation properties of the resulting LCEs was investigated. Because of the considerably low reactivity of the sec-butyl group toward the diacrylate in the LC monomer, only a densely crosslinked LCE was synthesized. Most interestingly, the mechanical properties, actuation temperature, and blocking stress of the LCEs comprising isobutyl groups were higher than those of the LCEs comprising n-butyl groups. This difference was attributed to the presence of branches in the LCEs with isobutyl groups, which resulted in a tighter molecular packing and reduced the free volume. Our results suggest a facile and effective method for synthesizing LCEs with tailored mechanical and actuation properties by the choice of chain extenders, which may advance the development of soft actuators for a variety of applications in aerospace, medicine, and optics.
在各种类型的形状变化材料中，液晶弹性体（LCEs）因其能够进行可编程的可逆形状转变而受到了广泛关注。LCEs的分子工程是控制其相变、机械性能和驱动性能的关键。在这项工作中，合成了侧链含有三种不同类型丁基（正丁基、异丁基和仲丁基）的LCEs，并研究了异构胺扩链剂对所得LCEs的热性能、机械性能和驱动性能的影响。由于仲丁基对LC单体中的二丙烯酸酯反应活性相当低，因此仅合成了一种高度交联的LCE。最有趣的是，含有异丁基的LCEs的机械性能、驱动温度和阻塞应力高于含有正丁基的LCEs。这种差异归因于含有异丁基的LCEs中存在支链，这导致了更紧密的分子堆积并减少了自由体积。我们的结果表明，通过选择扩链剂可以为合成具有定制机械和驱动性能的LCEs提供一种简便有效的方法，这可能会推动用于航空航天、医学和光学等各种应用的软致动器的发展。
