Synthesis and properties of transparent polyimides derived from trans-1,4-bis(2,3-dicarboxyphenoxy)cyclohexane dianhydride

A series of transparent polyimides was prepared from trans-1,4-bis(2,3-dicarboxyphenoxy)cyclohexane dianhydride (trans-3,3′-CHDPA) with various aromatic diamines via one-step solution polycondensation. The glass transition temperatures (Tgs) of the resulting polyimides were in the range of 206–255 °C. These polyimide films showed high optical transparency with cut-off wavelengths of 370–379 nm, and they exhibited good mechanical properties with tensile strengths of 65–88 MPa, tensile moduli of 1.7–2.4 GPa, and elongations at break of 4.7–7.5%. Compared with polyimides based on trans-1,4-bis(3,4-dicarboxyphenoxy)cyclohexane dianhydride (trans-4,4′-CHDPA), the polyimides derived from trans-3,3′-CHDPA showed higher Tg, better solubility and optical transparency due to the 3- and 4-position isomeric effect.