Structure - property behavior of new segmented polyurethanes and polyureas without use of chain extenders

Abstract

New novel segmented polyurethane and polyurea copolymers have been synthesized without chain extenders and the structure-property behavior of these systems has been investigated. It is shown that by the proper choice of diisocyanate and its symmetry, one can obtain highly microphase separated systems without chain extenders and that the materials also display useful mechanical behavior. In particular, it is shown that due to the bidentate hydrogen bonding achieved in the segmented ureas, a significant modulus "service temperature window" is also obtained. It is also verified that not only can strong microphase separation be obtained with low weight fraction hard segment content (14%) but that the hard phase, which is comprised of monodisperse "single molecule" units, also displays a percolated thread-like structure throughout the dominant soft segment material - the latter being based on ca. 1000 g/mol polytetramethylene oxide.