热致液晶聚酰胺的溶解性能和热性能

Dissolvability and Thermal Property of A Thermotropic Liquid Crystalline Polyamide

采用直接缩聚法,用自制的新型二元酸PEG3与芳香二胺进行缩聚反应,合成出较高分子量(比浓对数粘度为1.063 dL/g)的热致液晶聚酰胺,对其热性能和溶解性能进行了研究。结果表明,柔性链的引入,降低了聚酰胺的熔点(Tm=307.8℃),有利于液晶相的形成。而苯环的引入,平均分配了聚酰胺的刚性,既保持了聚酰胺耐热的特性,又提高了液晶相的稳定性(液晶显示范围ΔT=Ti-Tm=66.1℃),有利于该液晶高分子的应用。热失重(TGA)曲线显示了合成的聚酰胺具有较好的热稳定性(温度在400℃以上的质量损失为5%)。合成的聚酰胺具有较强的耐溶剂性,不溶于非极性溶剂,只能部分地溶解于强极性的纯溶剂或溶解于加盐(LiCl,或CaCl2)的复合溶剂中。

Via direct polycondensation method, a thermotropic liquid crystalline polyamide with a high moleculor weight（ηinh= 1.063dL/g） was prepared from the novel diacid PEG3 and a commercial aromatic diamine. The thermal and the deliquescent properties of the polyamide were studied. The result shows that the melting point（Tm= 307.8℃） of the polyamide was reduced effectively because of the introduction of flexible chain, which also favored the formation of liquid crystalline phase. Moreover, the phenyl rings introduced distributed evenly the rigidity of the polyamide, which maintained the heat-resistant characteristic of the polyamide, and increased the stability of the liquid crystalline phase（△T=Ti-Tm=66.1℃）, and favored the application of the liquid crystalline polymer. TGA showed good thermal stability of the poliamide, where the temperature for a mass loss of 5% was above 400℃. The solvent-resistance of the polyamide was good. It was not solvable in nonpolar solvents, and was soluble partly in strong polar, pure solvents, and soluble in saliferous complex solvents（ LiCl or CaCl2）.