Effect of photoacid generator on surface wettability controllable polyimides by UV light irradiation

Abstract

The authors have systematically investigated the surface wettability controllable polyimides by UV light irradiation using the polyimides having long-chain alkyl or bulky alkyl groups on their side chains. In this paper, the effects of the addition of photoacid generator or photobase generator were examined. As a result of examining the UV light irradiation (λmax; 254 nm) onto the polyimides based on the diamine monomer having long-chain alkyloxy groups and phenyl ester linkage (12G1-AG-terphenyl diamine), it was proven that the addition of the photoacid generator was effective for the surface wettability control from hydrophobicity to hydrophilicity. On the other hand, the addition of photobase generator was not effective. Therefore, it is speculated that the photoreaction activated by the acid catalyst such as an acid catalyzed ether cleavage and acid catalyzed photo-Fries rearrangement enhance the generation of hydrophilic groups such as hydroxyl groups after UV light irradiation. In case that the suitable photoacid generator were selected, the surface wettability control of these polyimides by UV light irradiation (λmax; 365 nm) were accomplished. The utilization of the UV light (λmax; 365 nm) is the merit in the practical use. From the result of ATR analyses, it is recognized that the hydrophobic alkyl groups on the polyimide surface decrease and the hydrophilic groups such as hydroxyl groups generate on their surface.