To extend the upper operating temperature range of melt processable PIs, two series of end-capped copolyimides based on hydroquinone diphthalic anhydride (HQDPA) isomers were designed by varying the contents of appropriate diamines. Thus, copolyimides PI-(0a∼20a) based on 3,3′-HQDPA were prepared by varying the ratio of rigid 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and flexible 4,4′-oxydianiline (ODA). The resulting copolyimides demonstrated good properties, such as excellent solubility, high T_g ranging from 328 to 354 °C as determined by dynamic mechanical analyzer (DMA), besides, exhibited good thermal stability based on 5% weight loss temperature (T_5%) of 502–514 °C and low melt viscosity in the range of 291–935 Pa·s. Most importantly, PI-20a showed a good combination of low melt viscosity simultaneously with significantly high T_g (328 °C). Furthermore, this system was modified by copolymerization with different feed ratio of 4,4′-HQDPA isomer and produced another series PI-(20a∼20e), that exhibited high T_g in the range of 315–330 °C with T_5% of 502–543 °C and minimum complex viscosity in the range of 291–479 Pa·s. All PIs form tough and flexible films that have remarkable tensile strength and moduli in the range of 93–116 MPa and 3.7–4.7 GPa, respectively.

为了扩大可熔融加工的PI的最高工作温度范围，通过改变适当的二胺含量设计了两个系列的基于对苯二酚二邻苯二甲酸酐（HQDPA）异构体的封端共聚酰亚胺。因此，通过改变刚性2-（4-氨基苯基）-5-氨基苯并咪唑（BIA）和柔性4,4'-氧二苯胺（ODA）的比例，可以制备基于3,3'-HQDPA的共聚酰亚胺PI-（0a〜20a）。 ）。所得共聚酰亚胺表现出良好的性能，例如出色的溶解度，动态力学分析仪（DMA）测定的328至354°C的高T _g，此外，基于5％的失重温度（T _5％）温度为502–514°C，熔体粘度低，范围为291–935 Pa·s。最重要的是，PI-20a表现出低熔体粘度与显着高的T _g（328°C）的良好组合。此外，该系统通过用4,4'- HQDPA异构体的不同的进料比共聚改性和产生的另一系列PI-（20a~20e），即表现出高的Ť_克在315-330℃的范围内与Ť _5％ 502-543°C的最大粘度和最小复数粘度在291-479 Pa·s的范围内。所有PI均形成韧性和柔性膜，其抗拉强度和模量分别在93-116 MPa和3.7-4.7 GPa范围内。