Preparation and Properties of Poly(urethane-imide) Films from Polyether Polyol: An Attempt to Nanoporous Polyimide Films.

A series of poly(urethane-imide) films were prepared by a reaction between poly(amide acid) and polyurethane prepolymer. Poly(amide acid) was prepared from pyromellitic dianhydride and 4, 4′-oxydianiline. Polyurethane prepolymer was prepared by a reaction of polyether polyol with tolylene-2, 4-diisocyanate and then with phenol as an endcap. The blend films obtained by casting and then drying were transparent. The films still remained transparent after heat treatment at 200°C. The films had characteristics of either elastomer or plastic depending on the polyurethane content. The elongation of the elastomer was as large as ca. 500-1000%. From viscoelastic analyses of the poly(urethane-imide) films, polyimide and polyurethane components were found to be phase separated in the film. By thermally decomposing only the thermally labile polyurethane domains at 300-400°C, polyimide films were obtained. The scanning electron microscopy of the polyimide films suggested the formation of pore of ca. 50nm size.