Grand canonical Monte Carlo simulations of a simple model semiflexible equilibrium polymer system,consisting of hard sphere monomers reversibly self-assembling into chains of arbitrary length,have been performed using a novel sampling method to add or remove multiple monomers during a single MC move.Systems with two different persistence lengths and a range of bond association constants have been studied.We find first-order lyotropic phase transitions between isotropic and nematic phases near the concentrations predicted by a statistical thermodynamic theory,but with significantly narrower coexistence regions.A possible contribution to the discrepancy between theory and simulation is that the length distribution of chains in the nematic phase is bi-exponential,differing from the simple exponential distribution found in the isotropic phase and predicted from a mean-field treatment of the nematic.The additional short length-scale characterizing the distribution appears to arise from the lower orientational order of short chains.The dependence of this length-scale on chemical potential,bond association constant,and total monomer concentration has been examined.
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