First shell substitution effects on hyperbranched polymers formed from monomers A2A2 and B3B3 with end-capping molecules

Hyperbranched polymers obtained by the polymerization of monomers A2A2 and B3B3 in the presence of end-capping molecules AR with a first shell substitution effect, FSSE, on the monomer B3B3 were investigated by a kinetic model. The profiles of the average degree of polymerization, degree of branching, and critical conversion under various compositions were calculated by a generating function method. It was found that, if groups B in excess of A, the curves of critical conversion A   of 100%, at which a gelation occurs, based on the initial compositions with substitution effect differ from that with equal reactivity of the groups B. The weight-average degree of polymerization, DP¯w, and degree of branching, DB, increase with increasing of the reactivity ratio of B. On the other hand, when the initial groups B are lower than A  , there is no apparent difference of the curves of critical conversion B of 100% between the polymerizations with and without FSSE. At high conversion of B, 99%, for example, the DP¯w and DB decrease with increasing of the end-capping molecules AR, but the DP¯w and DB are less influenced by the FSSE.

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