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High intrinsic thermally conductivity side-chain liquid crystalline polysiloxane films grafted with pendent difunctional mesogenic groups
Polymer Chemistry ( IF 4.6 ) Pub Date : 2022-06-15 , DOI: 10.1039/d2py00432a
Xiaole Zheng , Yingjie Zhan , Yingchun Liu , Maoping Lu , Enxiang Jiao , Hangzhen Zhang , Jun Shi , Mangeng Lu , Kun Wu

A series of polymers with high intrinsic thermal conductivity, named side-chain liquid crystal polysiloxanes (SCLCPs), is prepared via introducing a mesogenic structure using the monomers 4,4′-bis(5-hexenyloxy)biphenyl (S-CL) and 4-cyano-4′-hex-5-en-1-oxy-biphenyl (M). The effects of the flexible main chain and mesogenic units on the thermal conductivity properties are investigated in depth. S-CL is a crosslinking monomer and presents smectic liquid crystal texture, and it can be used as a difunctional monomer to avoid the introduction of non-mesogenic properties. Owing to the microscopic ordered structure obtained from S-CL and M, the thermal conductivity (λ) values of SCLCP5 in the through-plane (λ) and in-plane (λ) directions are 0.354 W m−1 K−1 and 1.585 W m−1 K−1, respectively, achieving a significant increase of 190.2% compared to SCLCP1. This is mainly due to the formation of a crosslinked structure and the orderly liquid crystal orientation, reducing the dissipation of phonons due to the random entanglement of molecular chains. In addition, the SCLCPs exhibit clear nematic liquid crystal structures, and as the amount of S-CL is increased the crystallite size calculated from XRD analysis gradually decreases, from 18 nm to 9 nm, and the crystal phase becomes more integrated and regular. Furthermore, SCLCPs present a wide service temperature range (22.75–323.3 °C) and good thermal stability (THeat resistance index (THRI): 194.7 °C). With the introduction of flexible segments, SCLCPs show better flexibility, further extending their possible applications in the field of thermoelectric materials.

中文翻译:

接枝有悬垂双官能介晶基团的高本征导热侧链液晶聚硅氧烷薄膜

通过使用单体 4,4'-双(5-己烯氧基)联苯 (S-CL) 和 4 -cyano-4'-hex-5-en-1-oxy-biphenyl (M)。深入研究了柔性主链和介晶单元对导热性能的影响。S-CL为交联单体,呈现近晶液晶结构,可作为双官能单体避免引入非介晶性质。由于从 S-CL 和 M 获得的微观有序结构,SCLCP5 在平面 ( λ ) 和平面内 ( λ ) 的热导率 ( λ ) 值) 方向分别为 0.354 W m -1 K -1和 1.585 W m -1 K -1,与 SCLCP1 相比实现了 190.2% 的显着增长。这主要是由于形成了交联结构和有序的液晶取向,减少了由于分子链的随机缠结而导致的声子耗散。此外,SCLCPs表现出清晰的向列液晶结构,随着S-CL量的增加,XRD分析计算出的微晶尺寸逐渐减小,从18 nm减小到9 nm,晶相变得更加完整和规则。此外,SCLCPs 具有较宽的使用温度范围(22.75–323.3 °C)和良好的热稳定性(T耐热指数( T HRI ):194.7 °C)。随着柔性段的引入,SCLCPs表现出更好的灵活性,进一步扩展了它们在热电材料领域的可能应用。
更新日期:2022-06-15
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