USING SOLUBILITY DIFFERENCE TO ACHIEVE SURFACE PHASE-SEPARATION IN DIMETHYLSILOXANE-UREA-URETHANE COPOLYMERS

Effects of the casting solvent on the surface compositions of a series of polydimethylsiloxane (PDMS)-urethane-urea copolymers were investig ated. The solvent pair investigated was tetrahydrofuran (THF) and mine ral spirits (MS). Factors that determine solubility of a copolymer in a mixture of THF and MS include the solvent composition and the ratio between the sizes of the soft and the hard segments. The effectiveness of using mixed solvent to enhance surface PDMS enrichment varies with the copolymer composition. The benefits are maximized when the averag e molecular weight of the PDMS segments is 10,000. (C) 1995 Academic P ress, Inc.