Computer simulation of end-linked elastomers. II. Bulk cured tetrafunctional networks

Abstract

Sol-gel distributions at high conversions, simulated by computer with spatial constraints on the distribution of chain ends, are reported for end-linked tetrafunctional systems. The composition of the sol is found to be uniquely dependent upon the functionality f of the cross linker: for f = 4, it mainly consists of linear monomers and oligomers containing one saturated cross linker. The molecular weight distribution of the sol exhibits a shoulder at the trimer due to the relative abundance of the "bow-tie" molecule. The populations of various types of dangling ends and loop defects in the gel are given and discussed. Our simulations reveal empirically that the single-loop probability varies with the - 3/8 power of the molecular weight of the prepolymers. The power-law dependence of the loop formation on chain length of the prepolymers and the nonrandom nature of the cross-linking reaction is discussed.