Synthesis of polyimides and their controlled surface wettability by UV irradiation

Abstract

Soluble polyimides were synthesized from novel diamine monomers having long-chain alkyl groups, unsaturated long-chain alkylene groups, natural products or photo-reactive groups, and a commercially available tetracarboxylic dianhydride. The thin films of those polyimides were irradiated by UV light (λmax; 254 nm or 365 nm), and the water contact angles decreased from nearly 100° (hydrophobic) to nearly 20° (hydrophilic) in proportion to the irradiated UV light energy. From the result of contact angle measurements and various surface analysis, it is recognized that the hydrophobic long-chain alkyl groups on the polyimide surface decrease and hydrophilic groups such as hydroxyl groups are generated on their surface. Thus, this technique is expected to be applied in the field of printed electronics as a method to pattern polyimide surfaces with hydrophobic and hydrophilic areas by UV light irradiation.