Biaxial nematic ordering of conjugated polymers modeled as ribbon-like chains

The electronic properties of conjugated polymers are intimately linked to the coherence of monomer orientations at the scale of the persistence length. The backbone tangent correlation can be partially captured by uniaxial nematic coupling using the worm-like chain model. The missing orientational correlation involving the normal directions requires the application of the recently developed ribbon-like chain (RLC) model. Here, we show that biaxial nematic ordering emerges from the RLC model containing orientational coupling. The phase diagrams including disordered, uniaxial nematic, and biaxial nematic phases are presented for ribbon-like polymeric chains. The effects of anisotropic bending stiffness, twist stiffness, and backbone length are addressed. This work provides a framework for connecting the monomer chemistry, which underlies the bending and twisting stiffness, and the mesoscale morphologies of polymers adopting ribbon-like conformations.