Synthesis of poly(urethane-imide) using aromatic secondary amine-blocked polyurethane prepolymer

Abstract

A set of poly(urethane-imide)s were prepared using blocked Polyurethane (PU) prepolymer and pyromellitic dianhydride (PMDA). The PU prepolymer was prepared by the reaction of polyether glycol and 2,4-tolylene diisocyanate, and end capped with N-methyl aniline. The PU prepolymer was reacted with PMDA until the evolution of carbon dioxide ceased. The effect of tertiary amine catalysts, organo tin catalysts, solvents, and reaction temperature were studied and compared with the poly(urethane-imide) prepared using phenol-blocked PU prepolymer. N-methyl aniline blocked PU prepolymer gave a higher molecular weight poly(urethane-imide) at a lower reaction temperature in a shorter time. Amine catalysts were found to be more efficient than organo tin catalysts. The reaction was favorable in particular with N-ethylmorpholine and diazabicyclo(2.2.2)octane (DABCO) as catalysts, and dimethylpropylene urea as a reaction medium. The poly(urethane-imide)s were characterized by FTIR, GPC, TGA, and DSC analyses. The molecular weight decreased with an increase in reaction temperature. The thermal stability of the PU was found to increase by the introduction of imide component. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4032–4037, 2000