POLYDIMETHYLSILOXANE UREA URETHANE COPOLYMERS WITH 1,4-BENZENEDIMETHANOL AS CHAIN EXTENDER

An investigation of polyurethanes and polyureas containing unusual diols directed toward the formation of minimally adhesive surfaces is reported. A two-step polymerization method was used to prepare dimethylsiloxane-urea-urethane copolymers with 1,4-benzenedimethanol as the chain extender. First, the reaction between isophorone diiisocyanate and benzenedimethanol was carried out in bulk at elevated temperatures without a catalyst. In the second stage, the reaction between aminopropyl end-capped dimethylsiloxane oligomers and diisocyanate intermediates was carried out in tetrahydrofuran solution at room temperature. Copolymers with chain extenders were found to be superior to those without chain extenders in thermal and mechanical properties. The improvements are due to the additional interactions between urea and urethane linkages. These interactions occur in both soft and hard segment domains.