EFFECT OF SOLVENT EVAPORATION RATE ON MICROPHASE-SEPARATED STRUCTURE OF SEGMENTED POLY(URETHANE-UREA) PREPARED BY SOLUTION CASTING

A useful instrument for polymer film preparation by solution casting w as employed in this study. It enabled us to control the solvent evapor ation rate of the polymer solution. By using this instrument, the aggr egation of hard segments in segmented poly(urethane-urea) (SPUU) was i nvestigated. SPUU was prepared from poly(tetramethylene oxide), 4,4'-d iphenylmethane diisocyanate and ethylenediamine. The effect of solvent evaporation rate on the microphase-separated structure of SPUU was el ucidated by dynamic mechanical analysis, tensile test, differential sc anning calorimetry analysis, small-angle X-ray scattering measurement, IR and IR dichroism analyses. The aggregation of hard segments in SPU U was observed to be affected considerably by the solvent evaporation rate of the cast film during the preparation. It was found that the sl ower the solvent evaporation rate, the higher the aggregation of hard segments to form rigid hard segment domains in SPUU. Nine months after casting, this casting effect still remained on the aggregation state of hard segments of SPUU films, although the interdomain spacing was n ot influenced by its rate.