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 χ ODT N . For polymers with low aspect ratios, fluctuations strongly elevate the phase transition χ ODT N at finite molecular weights. For high aspect-ratio polymers, chain semiflexibility decreases the phase transition χ ODT 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.