Fluctuation-induced orientational correlations in polymer blends and diblock copolymer melts

In this paper we study the possibility of fluctuation-induced orientational correlations in interacting polymer systems. We show how orientational correlations can arise solely from isotropic density fluctuations and the screened monomer potentials in the melt. No direct anisotropic interactions are introduced. The case of homopolymer and diblock copolymer blends are considered. For the diblock copolymers the fluctuation-induced anisotropy has a large effect on the shape of the molecule, whereas for homopolymers it is small and not important at the critical point.