  We describe a general implementation of the Fynewever-Yethiraj density
functional theory (DFT) for the investigation of nematic and cholesteric
self-assembly in arbitrary solutions of semi-flexible polymers. The basic
assumptions of the theory are discussed in the context of other generalised
Onsager descriptions for flexible polyatomic systems. The location of the
isotropic-to-nematic phase transition is found to be in good agreement with
molecular simulations for elongated chains up to relatively high polymer
flexibilities, although the predictions of the theory in the nematic regime
lead to gradual underestimations of order parameters with decreasing particle
stiffness. This shortcoming is attributed to increasing overestimations of the
molecular conformational entropy in higher-density phases, which may not be
easily addressed in the formalism of DFT for realistic particle models.
Practical consequences of these limitations are illustrated through the
application of DFT to systems of near-persistence-length DNA duplexes, whose
cholesteric behaviour is found to be strongly contingent on their detailed
accessible conformational space in concentrated solutions.
