Influence of preparation conditions on microdomain formation in poly(urethane urea) block copolymers

Selected poly(urethane urea) block copolymers were prepared under different conditions and their microphase-separated morphologies analyzed primarily with small-angle X-ray scattering (SAXS). Preparation conditions were varied by adjusting the temperature and vacuum pressure during solution casting. Copolymers with relatively high hard segment contents prepared under low vacuum conditions, where solvent is removed comparatively slowly and the copolymers spend a longer period of time in the presence of a plasticizer (i.e., solvent), produced films with higher degrees of phase separation. The longer casting times associated with the low vacuum pressure conditions also resulted in larger mean interdomain spacings. We speculate that this may be due to secondary hard domain coalescence. Attenuated total reflectance FT-IR and wide-angle X-ray diffraction experiments were performed, but these were not sensitive to the microdomain organization of these copolymers.