PHASE-BEHAVIOR OF SEMIFLEXIBLE DIBLOCK COPOLYMERS

We examine the phase behavior of diblock copolymers of arbitrary flexibility near their order-disorder transition. Our approach is based on a free energy functional calculated from a microscopic model of rigid rods connected with free joints and depends only on a small set of parameters, including the Flory chi parameter, a Maier-Saupe parameter, and the rod lengths and molecular weights of each block. By analyzing spinodals within this model, we have explored the effect of differences in flexibility between the two blocks, as well as the stiffness of the diblock as a whole, on the phase behavior. We find that nematic and microphase fluctuations can significantly affect transition temperatures and phase boundaries when the difference in stiffness is large.