Surface Wettability Controllable Polyimides Having Unsaturated Long-chain Alkyl Groups

Novel diamine monomers having unsaturated long-chain alkyl group (Oleoyl-DA) and saturated long-chain alkyl group (Stearoyl-DA) were synthesized from dibromo benzoic acid. The novel polyimides and copolyimides were synthesized from 3,4'-ODPA as a dianhydride, above diamines having unsaturated long-chain alkyl group or saturated long-chain alkyl group, and DDE as a diamine co-monomer by two step polymerization systems. The thin films of obtained polyimides were irradiated by UV light (lambda max; 254 nm), and the contact angles for the water decreased from near 90 degrees (hydrophobicity) to minimum 30 degrees (hydrophilicity) in proportion to irradiated UV light energy. From the result of surface analyses such as ATR and XPS, it is recognized that the hydrophobic groups on the polyimide surface decrease and the hydrophilic groups such as hydroxyl groups and carboxyl groups generate on their surface. Furthermore, it is considered that the oxidation of double bond in the unsaturated long-chain alkyl group significantly affect the changes of wettability by UV light irradiation based on the various analyses.