Postgel properties in the statistical crosslinking of heterochains. II. Free-radical crosslinking copolymerization

The heterochain crosslinking theory is applied to postgel behavior in the f ree-radical crosslinking copolymerization of vinyl and divinyl monomers. In this context, the crosslinked polymer formation can be viewed as a system in which the primary chains formed at different times are combined in accor dance with the statistical chain-connection rule governed by the chemical r eaction kinetics. Because the primary chains are formed consecutively, the number of chain types N must be extrapolated to infinity, N --> infinity. P ractically, such extrapolation can be conducted with the calculated values for only three different N values. The analytical expressions for the weigh t; fraction and average molecular weights of the sol fraction are derived f or the general primary chain length distribution function in free-radical p olymerization. Illustrative calculations show that the obtained results agr ee with those from the Monte Carlo method, and that the postgel properties in free-radical crosslinking copolymerization systems could be significantl y different from those in randomly crosslinked systems. (C) 2000 John Wiley & Sons, Inc.