A simulation model of hard spheres capable of reversible assembly into chains,which then may reversibly cross-link into networks,has been studied through grand canonical Monte Carlo simulation.Effects of varying intra-and interchain bond strengths,chain flexibilities,and restrictions on cross-linking angle were investigated.Observations including chain-length distributions and phase separation could be captured in most cases using a simple model theory.The coupling of chain growth to cross-linking was shown to be highly sensitive to the treatment of cross-linking by chain ends.In some systems,ladderlike domains of several cross-links joining two chains were common,resulting from cooperativity in the cross-linking.Extended to account for this phenomenon,the model theory predicts that such cooperativity will suppress phase separation in weakly polymerizing chains and at high cross-link concentration.In the present model,cross-linking stabilizes the isotropic phase with respect to the nematic phase,causing a shift in the isotropic-nematic transition to higher monomer concentration than in simple equilibrium polymers.
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