Entropy effect of alkyl tails on phase behaviors of side-chain-jacketed polyacetylenes: Columnar phase and isotropic phase reentry
Entropy effect of alkyl tails on phase behaviors of side-chain-jacketed polyacetylenes: Columnar phase and isotropic phase reentry
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DOI：
10.1016/j.polymer.2016.02.012
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发表时间：
2016-03
期刊：
影响因子：
4.6
通讯作者：
Xiao-Qing Liu;Jun Wang;Shuang Yang;Yongfeng Men;Pingchuan Sun;E. Chen
中科院分区：
文献类型：
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作者：
Xiao-Qing Liu;Jun Wang;Shuang Yang;Yongfeng Men;Pingchuan Sun;E. Chen
本文研究了一系列聚苯乙炔衍生物聚[二（正烷基）乙炔基丙烯酸酯]（Pn，为正烷基的碳原子数，从2到14）的相行为。短烷基（n≤ 6）的Pns由于侧链的“夹套效应”而形成柱状液晶（Col）相。随着烷基链长的增加（n≥ 8），在低温下的层状相（Lam）和高温下的Col相之间形成了一个各向同性相，可以认为是一个可重入相（Ire）。这种不寻常的相行为是由侧链的运动状态决定的。通过原位变温固体核磁共振实验，区分了主链和侧链在不同相中的运动，为侧链在Pns（n≥ 8）中的熵效应提供了有力的证据。
We have investigated phase behaviors of a series of polyphenylacetylene derivatives, poly[di(n-alkyl) ethynylterephthalates] (Pn,nis the number of carbon atoms ofn-alkyl group, from 2 to 14), which are largely influenced by the length ofn-alkyl tails on 2,5-position of the phenyl group. With short alkyl groups (n≤ 6),Pns form columnar liquid crystalline (Col) phases due to the “jacketing effect” of side-chains. As the alkyl tails become longer (n≥ 8), an isotropic phase, which can be considered as a reentrant one (Ire), is identified between lamellar phase (Lam) at low temperatures and Col phase at high temperatures. This unusual phase behavior is determined by the motional state of the side-chains. Thanks to in-situ variable temperature solid-state NMR experiments, the motion of main- and side-chains in different phases were distinguished, providing strong evidence for the entropy effect of side-chains which drives Ireand then Col phase inPns (n≥ 8) upon heating.