Structure and morphology of segmented polyurethanes: 2. Influence of reactant incompatibility

By following the copolymerization of a model polyurethane system, HTP B D /2,6 (or 2.4 )-TD I /B DO, byoptical microscopy, it was found that initial reactant incompatibility was the key factor in determining thefinal morphology of bulk sample. Based on this finding and the esults from the previous paper, modelsare proposed to describe the morphology during polymerization of this particular polyurethane systemfor several hard segment compositions where both macro-phase separation and micro-phase separationof reactants can occur during polymerization. The copolymerization of one seemingly compatiblesystem, PPO-EO/MDl/BDO, which has been previously studied and commercially produced, was alsofollowed by optical microscopy. In the size range which can be detected with an optical microscopeusing conventional optics, no heterogeneities were observable at the beginning of this reaction butphase separation was evident later in the reaction and can be xplained by the presence of micro-phaseseparation of reactants. Globule and spherulite formation and the presence of multiple T(g)\u27s and T(m)\u27sobserved by previous workers can be explained by the two levels of heterogenities present duringpolymerization