Surface Wettability Controllable Polyimides by UV Light Irradiation for Printed Electronics

The soluble polyimides were synthesized from diamine monomers having hydrophobic groups such as long-chain alkyl groups, tetracarboxylic dianhydrides such as 3,4'-ODPA (a-ODPA), and DDE as a diamine co-monomer. The thin films of obtained polyimides were irradiated by UV light (lambda max; 254 nm or 365 nm), and the contact angles for the water decreased from near 100 degrees (hydrophobicity) to near 20 degrees (hydrophilicity) in proportion to irradiated UV light energy. From the result of contact angle measurements and the result of the ATR and XPS analysis, it is recognized that the hydrophobic groups on the polyimide surface decrease and the hydrophilic groups such as a carboxyl group and a hydroxyl group generate on their surface. Thus, the surface wettability of these polyimides can be controlled by UV light irradiation, and these methods are expected to be applied in the field of printed electronics.