Surface and molecular modification of polyimides via graft copolymerization and functionalization

Abstract

Surface and molecular graft polymerization technique have been employed on the modification and functionalization of polyimide (PI) and fluorinated polyimide (FPI) involved in the microelectronics and membrane applications. Electroless plating of copper via a Sn-free activation process was carried out effectively on PI and FPI films modified by plasma or UV-induced graft copolymerization with N-containing monomers. The graft-modified PI and FPI surfaces show good adhesion property with electrolessly deposited copper via the formation of covalent bonds. Nanoporous PI and FPI films were first prepared by the molecular graft copolymerization approach. Dielectric constant as low as 2.1 and 1.9 were obtained for the resulting nanoporous PI and FPI films, respectively. Fluorinated polyimides with grafted side chains were successfully synthesized through molecular graft copolymerization of acrylic acid (AAc), 4-vinylpyridine (4VP), N-isopropylacrylamide (NIPAAm) with the ozone-preactivated FPI backbone. Microfiltration membranes prepared from these copolymers by phase inversion technique exhibit strongly pH- or temperature-sensitive properties.