低热膨胀系数超支化共聚聚酰亚胺的构建及性能

Synthesis and Properties of Hyperbranched Polyimide with Low Thermal Expansion Coefficient

以2,3,3',4'-联苯四甲酸二酐、3,3',4,4'-联苯四羧酸二酐、对二氨基二苯醚、对苯二胺和合成三胺单体为原料,合成了含有超支化链段的新型共聚聚酰亚胺。研究表明,与线型低热膨胀系数聚酰亚胺(HB-Co-PIS-0)相比,超支化链段引入后,其显著的优点是溶解性变好,引入超支化链段5%时,聚酰亚胺可在极性大的溶剂二甲基甲酰胺和甲基吡咯烷酮中溶解,在四氢呋喃等极性小的溶剂中回流微溶。另外,其聚酰亚胺酸黏度降低,热膨胀系数值维持较低的数值,无序结构增多,玻璃化温度和热分解温度降低,拉伸强度增大,断裂伸长率减小。并且,超支化链段引入,使原线型低热膨胀系数聚酰亚胺微突起的致密表面变为更多纳米突起的粗糙疏松表面,水接触角从原来72°增加到76°(3%超支化)和85°(5%超支化)。

A series of hyperbranched copolyimides were prepared by thermal imidization of poly（amic acid） s derived from 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride,2,3＇,3,4＇-biphenyltetracarboxylic dianhydride,p-phenylenediamine,4,4＇-oxydialinine and triamine prepared by ourselves. The results show that the synthesized hyperbranched copolyimide exhibits excellent solubility. They could soluble in the polar solvent of N,N-dimethylformamide（DMF） and N-methyl pyrrolidone（NMP）,or slightly soluble in tetrahydrofuran（THF） with small polarity. The synthesized hyperbranched polyamic acid also exhibits lower viscosity than the linear polyamic acid. And the synthesized hyperbranched copolyimide shows low coefficient of thermal expansion,only increases from 13× 10-6/℃ to 26× 10-6/℃（5% hyperbranched）. Compared with linear polyimide,the synthesized hyperbranched copolyimide has more disordered structure,increased tensile strength and decreased elongation at break. Moreover,with introduced the hyperbranched segments into the linear polyimide,the compact surfaces with micro protrusions become more loose and rough with nano protrusions,and the contact angles of copolyimides increase from 72° for linear copolyimide,to 76° for 3% hyperbranched segments in the main chain of copolymer up to 85° for 5% of hyperbranched segments in the main chain of copolymer.