BLENDS OF METAL ACETATES AND POLYURETHANES CONTAINING PYRIDINE GROUPS

Two series of segmented polyurethanes based on 3/2/1 and 2/1/1 molar r atios of methylene diphenyldiisocyanate (MDI), NN-bis(2-hydroxyethyl)i sonicotinamide (BIN), and poly(tetramethylene oxide) (PTMO, MW = 1000) were synthesized and blended with different metal acetates. The therm al behavior and mechanical properties of the pyridine-containing polyu rethane precursors and their blends were characterized by DSC, DMTA, a nd tensile testing. The results suggest that coordination between pyri dine groups in the hard segments and the metal ions in the acetates im proves hard-domain cohesion and phase separation and, subsequently, ha s an effect on mechanical properties. The varying ability of the pyrid ine group to coordinate with different cations results in different ex tents of phase separation. The interaction of pyridine with Ni or Cu ( II) is much stronger than with Zn. It is shown that coordination inter actions can be a driving force for phase separation and hard-domain ag gregation in multiblock copolymer systems. Two different morphologies are proposed for polyurethanes of differing stoichiometry to explain t he differences in the results from DMTA and tensile testing. (C) 1994 John Wiley & Sons, Inc.