A series of homopolyimides and copolyimides based on isomeric biphenyl dianhydrides[2,2' ,3, 3' -biphenyltetracarboxylic dianhydride (3,3' -BPDA ), 2.3' ,3,4' -biphenyl tetracarboxylic dianhydride (3,4' -BPDA ) and 3, 3' ,4,4' -biphenyltetracarboxylic dianhydride (4,4' -BPDA )] were prepared, then the thermal and mechanical properties of the polyimides were studied comparatively. The results showed that when the structures of diamine were same, polyimides based on 3, 3' -BPDA and 3,4' -BPDA had higher glass translation temperature ( Tg) and better thermo-processability than those derived from 4,4' -BPDA, when the structures of dianhydride were same, Tg of polyimides based on para-diamine ( PDA ) was better than that of polyimides based on 4,4' -diaminodiphenyl ether ( ODA ). Polyimide based on 3,4' -BPDA / PDA showed the highest Tg of 382 ℃ , the tensile strength and modulus of the corresponding film was 100 MPa and 1.8 GPa respectively, and the elongation at break was about 12% . Film made from polyimide based on 4,4' -BPDA/PDA had the best tensile properties, the tensile strength was 307 MPa, the tensile modulus was 4.1 GPa, and the elongation at break was about 23% . Polyimide moulding plastics based on 3,4' -BPDA/ODA and 3,3' -BPDA/4,4' -BPDA (1 / 1) /ODA had Tg above 300 ℃ and better mechnical properties, the impact strength of them were 82.3 kJ/m2和94 kJ / m2 respectively.%制备了一系列基于异构联苯二酐[2,2’,3,3’-联苯四甲酸二酐(3,3’-BPDA)、2,3’,3,4’-联苯四甲酸二酐(3,4’-BPDA)和3,3’,4,4’-联苯四甲酸二酐(4,4’-BPDA)]的聚酰亚胺(PI)均聚物和共聚物,比较研究了这些聚合物的热学和力学性能.结果表明,当二胺结构相同时,基于3,3’-BPDA和3,4’-BPDA的PI均聚物或共聚物较基于4,4’-BPDA的均聚物有更高的玻璃化转变温度(Tg)和更好的热加工性；当二酐结构相同时,基于对苯二胺( PDA)的PI的Tg高于基于4,4’-二氨基二苯醚(ODA)的PI.基于3,4’-BPDA/PDA的PI具有最高的Tg,其值为382C,由其制备的薄膜的拉伸强度为100 MPa,拉伸弹性模量为1.8 GPa,断裂伸长率为12％.基于4,4’-BPDA /PDA的PI薄膜具有最高的拉伸性能,其拉伸强度为307 MPa,拉伸弹性模量为4.1 GPa,断裂伸长率为23％.基于3,4’-BPDA/ODA和3,3’-BPDA/4,4’-BPDA(1/1)/ODA的PI模塑料均具有高于300℃的Tg和较好的力学性能,其冲击强度分别达到82.3 kJ/m2和94 kJ/m2.
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