Fluctuation Effects in Semiflexible Diblock Copolymers

We present a simulation study of the equilibrium thermodynamic behavior of semiflexible diblock copolymer melts. Using discretized wormlike chains and field-theoretic Monte Carlo, we find that concentration fluctuations play a critical role in controlling phase transitions of semiflexible diblock copolymers. Polymer flexibility and aspect ratio control the order–disorder transition Flory–Huggins parameter χODT N. For polymers with low aspect ratios, fluctuations strongly elevate the phase transition χODT N at finite molecular weights. For high aspect-ratio polymers, chain semiflexibility decreases the phase transition χODT N. We find that the simulated phase behavior agrees well with our recently developed fluctuation theory based on wormlike chain configurations and a one-loop treatment of concentration fluctuations.