Homogenization process caused by competition between phase separation and ester-interchange reactions in immiscible polyester blends: A Monte Carlo simulation

The homogenization process caused by competition between phase separation a nd ester-interchange reactions in immiscible polyester blends was investiga ted via the Monte Carlo simulation method. Phase separation and ester-inter change reactions were performed simultaneously with the one-site bond fluct uation model on a homogeneous blend of immiscible polyesters. Three differe nt values of the repulsive pair-interaction energy (E-AB) between segments A and B and two trial ratios of phase separation to ester-interchange react ions at a given E-AB were introduced to examine the competition between the m. Phase separation was monitored by the calculation of the collective stru cture factor, and copolymerization was traced by the calculation of the deg ree of randomness (DR). In all cases, as the homogenization proceeded, the maximum intensity of the collective structure factor initially increased, r eached a maximum, and finally decreased, whereas the peak position where th e structure factor had a maximum shifted downward in the early stage and th en remained unchanged after the intensity of the collective structure facto r reached the maximum. This indicates that during the homogenization proces s, the domain size did not change significantly after phase-separated struc tures were developed distinctly. In this simulation, phase-separated struct ures were traced until the DR was above 0.8. This result indicates that hom ogenization can be accomplished via homogeneous ester-interchange reactions over most of the polyester chains because copolyesters resulting from este r-interchange reactions do not act as an efficient compatibilizer. (C) 2000 John Wiley & Sons, Inc.