Monte Carlo simulations of free chains in end-linked polymer networks

The structural properties of end-linked polymer networks prepared in the presence of inert linear chain solvent were investigated with Monte Carlo simulations using the three-dimensional bond fluctuation model on a simple cubic lattice. Networks of 50-mer precursor chains were prepared in a solvent of 50-mer inert linear chains with a series of concentrations and two ratios, r, of cross-link sites to chain ends. The networks were formed under both stoichiometric (r=1) and optimal (r=1.2) conditions for minimizing the network imperfections and soluble material and maximizing the elastic material. A maximum is observed in the fraction of elastic material at small degrees of dilution and is explained in terms of entanglement effects. The conformational behavior of a small concentration of linear 50-mer probe chains trapped in end-linked networks of mesh sizes ranging from 10- to 50-mer was also studied. The radius of gyration of the linear chains was found to decrease with decreasing mesh size of the host network, in agreement with a theoretical scaling relationship; but the magnitude of the effect is small.