Anomalous Concentration Effects on Phase Behavior and Nematic Order in Mixtures of Side-Chain Liquid Crystal Polymers and Low-Molecular-Weight Liquid Crystals

We study the anomalous concentration effects in mixtures of side-chain liquid crystalline polymers (SCLCPs) and low-molecular-weight liquid crystals (LMWLCs) by modifying the theory of Brochard, Jouffroy, and Levinson (BJL) to include the effects of the polymer backbone. Our new theory considers both the interaction of the polymer backbone with the global nematic field, as well as the local steric constraints due to the grafting of the side groups onto the polymer backbone. In addition, we consider the enhancement in the coupling between the pedant mesogens and the LMWLC molecules as the SCLCP concentration increases. The resulting phase diagram and nematic order parameters are in qualitative agreement with experimental observations, but drastically different from the predictions by the BJL theory.