Properties of Polyurethane Anionomers: Ionization via Bimolecular Nucleophilic Displacement of the Urethane Hydrogen

摘要

Two series of polyether polyurethane anionomers based on 4,4' diphenylmethane diisocyanate (MDI) and polytetramethylene oxide (PTMO) were synthesized and their properties investigated. Ionization proceeded via a biomolecular nucleophilic displacement reaction with sodium hydride followed by a ring opening reaction with gamma-propane sultone. The lower hard segment content (20 wt% MDI) control material exhibited an initial one phase morphology that underwent phase separation upon ionization with subsequent development of hard segment ordering. These changes in morphology were accompanied by dramatic improvements in mechanical properties. The 38 wt% MDI control material possessed a two phase morphology and well developed hard segment ordering. Ionization disrupted the hard segment ordering and at low levels decreased the degree of phase separation. Further ionization led to reattainment of the original degree of phase separation and a marked improvement in mechanical strength. The differences in properties of the two series of materials are discussed and compared with properties of other polyurethane ionomers reported in the literature.