无柔性间隔基侧链型液晶高分子复合定形相变材料的制备与性能研究

Preparation and Properties of Form-stable Phase Change Materials Based on Side-chain Liquid Crystal Polymer without Flexible Spacer

设计合成了一系列具有不同烷氧基尾链长度的单体4′-烷氧基-4-联苯酚甲基丙烯酸酯Mbi Cm(m=1,2,4,6,8,10,12,14,16,18),通过自由基聚合方法合成了相应的具有不同烷氧基尾链长度的无柔性间隔基侧链型液晶高分子PMbi Cm,将所得的侧链型液晶高分子和相变材料石蜡按一定质量比混合,通过"加热-冷却法"成功制备了定形相变材料.通过凝胶测试发现当尾链长度为m=12,14,16,18时,高分子对固体石蜡具有良好的凝胶定形效果,且随着烷氧基尾链的增长,聚合物和石蜡的相容性增加,最低凝胶浓度降低,得到定形相变材料的凝胶解缔温度也相应下降.通过示差扫描量热法(DSC)、热重分析法(TG)、流变(Rheology)等测试考察了定形相变材料的相变储能性能、热稳定性和流变性能,实验结果表明该定形相变材料具有相变焓值高、热稳定性好、凝胶强度高等优点.通过红外光谱(FTIR)、偏光显微镜(POM)和扫描电镜(SEM)等测试发现PMbi Cm通过非共价键作用力自聚集形成三维凝胶网络结构,对石蜡起固定支撑作用.

A series of monomers 4＇-alkoxy-4-biphenol methacrylates MbiCm, with different alkoxy tail lengths （m = 1, 2, 4, 6, 8, 10, 12, 14, 16, 18）, and their corresponding polymers PMbiCm were synthesized via free radical solution polymerization. The phase transition temperature and thermal stability of the polymers were studied by DSC and TG. Experimental results revealed that all the polymers were liquid crystal and exhibited high clear points. The clear point of the polymers was first decreased and then increased with increasing the alkoxy chain length. All the polymers showed excellent thermal stability, and their decomposition temperatures were all above 310 ℃. The novel P6biCm/paraffin composite, form-stable phase change materials （FSPCM）, was prepared by introducing PMbiCm into paraffin. The minimum gelation concentration （MGC） and gel-to-sol transition temperature （TGS） were tested by tube-testing method. It was found that the gelation stability of PMbiCm was closely linked with alkoxy chain length. PMbiCm （m = 1, 2, 4, 6） were insoluble in paraffin at high temperature, and not able to form gel in pa（affin. PMbiCm （m = 8, 10） were partly paraffin-soluble, while PMbiCm （m = 12, 14, 16, 18） formed stable gel in paraffin. The MGC and TGS decreased with the increase of the alkoxy tail length owing to enhanced interaction between the polymer and paraffin. The thermal properties and rheological properties were studied. The results showed that the PMbiCm/paraffin were of high phase transition enthalpy, excellent thermal stability and high gel strength. The structure and morphology of the FSPCMs were also investigated by FTIR, POM and SEM. The results revealed that paraffin was restricted because the gelators PMbiCm could self-assemble into three-dimensional netted structures, leading to the formation of shape-stable PCMs without leakage even above their melting point of the phase change materials.