Synthesis and Characterization of Semi-Aliphatic Polyimide Films with Excellent Comprehensive Performance

Transparent polyimide films with excellent comprehensive properties may be indispensable to next-generation optoelectronic and flexible display applications. To date, the most studied transparent polyimide films are mainly prepared with alicyclic dianhydride as monomer, but the related properties of such films are not satisfactory. In this work, two series of highly optically transparent copolyimide films were prepared by the polycondensation of dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexane-tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride with 4,4'-oxydianiline via a facile one-step method. Through the optimization of structure and composition, the relationship between structure and properties of copolymerized semi-alicyclic polyimide was studied. The prepared copolyimide films show good thermal stability: glass transition temperatures in the range of 264–315°C and 5% weight loss temperature of 463–527°C, superior optical transparency up to 90%. Specifically, these copolyimide films have tensile strength greater than 90.3 MPa.