CROSS-LINKING OF POLY(METHYL METHACRYLATE) BY AMINOLYSIS OF ESTER FUNCTIONS WITH DIAMINES

The cross-linking of poly(methyl methacrylate) (PMMA) macromolecules b y primary aliphatic diamines was carried out at 413-473 K, above the p olymer glass transition temperature. The spherical grains of the suspe nsion-prepared polymer (0.25-0.8 mm) and the molar ratio to amine abov e 20 were used. The reaction is characterized by an induction period b efore the macroscopic gel was observed and by fast network formation. Both phenomena are temperature-dependent (87 +/- 2 kJ mol-1). The rate of gelation is dependent also on the type of diamine; the shorter ind uction period of gelation and the higher rate of cross-linking were ob served when amino groups were separated with longer alkyl chains. From the kinetics of amine uptake with PMMA, however, it can be concluded that gel formation is influenced also by the reactivity of amine in th e transamination reaction and by the amount of bounded diamine. Aminol ysis of PMMA ester groups proceeds from the very beginning of heating of the reaction charge. The polymer cross-linking prevails when there is more than 60% of diamine attached to PMMA in dependence on the amin e type used. (C) 1995 John Wiley & Sons, Inc.