Preparation and characterization of hyperbranched polyimides based on 4,4',4''-triaminotriphenyl-methane

Abstract

This work focuses on the preparation and characterization of novel hyperbranched polyimides based on commercially available 4,4,'4''- triaminotriphenylmethane and pyromellitic dianhydride or 4,4'-oxydiphthalic anhydride. The bi- and trifunctional monomers were reacted in a molar ratio of 1:1 or 2:1 to prepare polyimide precursors (hyperbranched polyamic acids) end-capped with either amino or anhydride groups. The precursors were then transformed into hyperbranched polyimides using thermal imidization. The final products were self-standing films, whose thermal behaviour was characterized by having no weight loss up to 250 °C and by having glass transition temperatures above 200 °C. We monitored the permeability of carbon dioxide, organic vapours and water vapour through these membranes. We also compared the properties of these materials with linear polyimides based on 4,4'-methylenedianiline combined with either pyromellitic dianhydride or 4,4'-oxydiphthalic anhydride.