Preparation and Characterization of Novel Polyimides with Hydroxyl Groups

3,3′-diamino-4,4′-dihydroxybiphenyl (DADHBP) was synthesized and its chemical structure was confirmed by Fourier transform infrared (FT-IR) spectroscopy, ¹H-nuclear magnetic resonance (¹H-NMR), and differential scanning calorimetry (DSC). Then six poly(amic acid) (PAA) solutions were prepared by copolymerization of DADHBP, oxydiphthalicanhydride (ODPA), and 2,2-bis 4-(4-aminophenoxy)phenyl] propane (BAPOPP) in N,N-dimethylacetamide (DMAC) in different mole ratios. The polyimide (PI) films were obtained through thermal imidazation reactions of the thin layers of the above-mentioned precursor solutions. Chemical structures of all PI films were demonstrated by FT-IR. Thermal stabilities and decomposition behaviors of the PI films were tested by DSC and thermogravimetric analysis (TGA). Thermal measurements indicate that the polymers have high thermal stability and produce high char yields. The properties of the PI films were further studied by ultraviolet–visible spectroscopy, water absorption, surface energy, and mechanical measurements. Thermal analysis showed glass transition temperatures between 205.9°C and 276.7°C. Decomposition temperatures were higher than 360.2°C, with 10% weight losses in the range of 448.6°C～517.8°C. The prepared PI films also exhibited good UV absorption, low water absorption (<2%), low surface energy (<44.28 mJ/m²), and good mechanical properties.