Calculation of the free energy of polymeric systems in terms of compositional and orientational order parameters

We present a general framework for the calculation of the free energy functional of inhomogeneous polymeric systems in terms of the compositional scalar order parameter phi and the orientational order parameters of second-rank tensor Q(ij). Our formalism is a straightforward extension of the density functional theory developed by Tang and Freed [J. Chem. Phys. 94, 1572 (1991)] and the contribution of the conformational entropy is given in terms of the gradient expansion. As a demonstration, we give an exact expression for the free energy of Gaussian chains up to second order in the gradients. (C) 2001 American Institute of Physics.