Influence of molecular weight on the phase behaviors of comb‐like polymers with long n‐alkyl side chains based on mesogen‐jacketed liquid crystalline polymers
Influence of molecular weight on the phase behaviors of comb‐like polymers with long n‐alkyl side chains based on mesogen‐jacketed liquid crystalline polymers
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DOI：
10.1002/pola.26453
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发表时间：
2013-02
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影响因子：
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通讯作者：
Sheng Chen;Haiyuan Luo;He-Lou Xie;Hailiang Zhang
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文献类型：
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作者：
Sheng Chen;Haiyuan Luo;He-Lou Xie;Hailiang Zhang
通过原子转移自由基聚合（ATRP）合成了一系列具有不同分子量（Mn）和低分子量分布的梳状聚合物聚{2，5-双[（4-十八烷氧基苯基）氧羰基]苯乙烯}（P-OC 18 s）。的相行为进行了研究，包括差示扫描量热法，偏光显微镜，广角X-射线衍射和变温FTIR光谱的技术相结合。一方面，聚合物中的液晶基元对烷基尾链的相行为有很大的影响，导致烷基尾链的堆积性差，熔点低;另一方面，发现聚合物的液晶相结构强烈依赖于锰。Mn ≤ 4.6 × 104的样品在低温下形成近晶相，在高温下形成各向同性相。Mn ≥ 5.2 × 104的样品显示出一个分隔近晶相和柱状晶相的各向同性的重入相。同时，实验结果表明，随着MnS含量的增加，玻璃化温度和近晶相向各向同性相的转变温度均略有升高，而各向同性相向柱状相的转变温度则随着MnS含量的增加而急剧降低。各向同性相的再现是由于焓驱动力和熵驱动力之间的竞争。© 2012 Wiley Periodicals，Inc. J Polym Sci Part A：Polym Chem，2013
A series of comb-like polymers, poly{2,5-bis[(4-octadecyloxyphenyl)oxycarbonyl]-styrenes{ (P-OC18s) with different molecular weights (Mn) and low molecular weight distributions have been successfully synthesized via atom transfer radical polymerization. The phase behaviors have been investigated by a combination of techniques including differential scanning calorimetry, polarized optical microscopy, wide-angle X-ray diffraction, and temperature-variable FTIR spectroscopy. One hand, phase behaviors of the alkyl tails were strongly influenced by the mesogens of polymers, leading to the poor packing of the alkyl tails and the low melting. The other hand, the liquid crystalline phase structures of polymers were found to be strongly Mn dependent. The samples with Mn ≤ 4.6 × 104 formed a smectic phase in low temperature and an isotropic phase in high temperature. The samples with Mn ≥ 5.2 × 104 displayed a reentrant isotropic phase, which was separating the smectic phase and columnar nematic phase. Meantime, the experiment results showed that the glass temperature and the transition temperature from smectic phase to isotropic phase both slightly increased with the increase of MnS; however, the transition temperature from isotropic phase to columnar phase sharply decreased with the MnS improved. The reappearance of isotropic phase is due to the competing between the driving force of the enthalpy and the driving force of the entropy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013