Synthesis and properties of transparent polyimides derived from 1,4-cyclohexylene bis(trimellitate anhydride)

A series of polyimides (PIs) derived from 1,4-cyclohexylene bis(trimellitate anhydride) (TACH) was synthesized by conventional two-step method with chemical imidization. The resulting PIs had glass transition temperatures (T(g)s) in the range of 188-240 degrees C and exhibited good mechanical properties with tensile strengths of 50.0-90.2 MPa, tensile moduli of 2.2-3.9 GPa, and elongations at break of 2.9-5.8%. These PI films showed high optical transparency with cut-off wavelengths of 345-369 nm and high transmittance at 500 nm with more than 84%. Compared with PIs derived from 1,4-bis(3,4-dicarboxyphenoxy)cyclohexane dianhydride, the TACH-based PIs showed higher T-g, better solubility, and competitive transparency