Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers

Abstract

Electronic and optical properties of conjugated polymers are strongly affected by their solid-state microstructure. In nematic polymers, mesoscopic order and structure can be theoretically understood using Maier-Saupe (MS) models, motivating us to apply them to conjugated macromolecular systems and consider the problem of their material-specific parameterization. MS models represent polymers by worm-like chains (WLC) and can describe collective polymer alignment through anisotropic MS interactions. Their strength is controlled by a phenomenological temperature-dependent parameter, υ(T). We undertake the challenging task of estimating material-specific υ(T), combining experiments and Self-Consistent Field theory (SCFT). Considering three different materials and a spectrum of molecular weights, we cover the cases of rod-like, semi-flexible, and flexible conjugated polymers. The temperature of the isotropic-nematic transition, TIN, is identified via polarized optical microscopy and spectroscopy. The polymers...