Form birefringence of block copolymer melts under oscillatory shear

When block copolymer melts are subjected to an external flow field, such as simple shear flow, composition fluctuations are distorted by the velocity field and take on an anisotropic character. This leads to anisotropy in the macroscopic dielectric tensor, which is manifested in optical experiments as form birefringence or dichroism. 

At temperatures near the microphase separation transition in block copolymer melts, the amplitudes of the fluctuations become very large, giving rise to singular behavior of the birefringence. We employ a mean field theory for the dynamics of homogeneous block copolymer melts to calculate the form birefringence of a diblock melt subjected to low- amplitude oscillatory shear.