Helix-coil and solvation-induced reentrant nematic-smectic A transitions in a polypeptide solution

A simple model is introduced to describe re-entrant isotropic-nematic and nematic-smectic A phase transitions mediated helix-coil transition and solvation within individual liquid crystalline semiflexible polymers in a solution. We consider hydrogen bonding between the polymer and solvent molecules (solvation) as an intermolecular interaction and helix-coil transformations of the polymer as an intramolecular interaction. The helix part is rigid and can form nematic and smectic A phases. On the other hand, the solvation prevents liquid crystalline ordering of the polymer chains. At high temperatures, a polymer is in a coiled state without solvation. With decreasing temperatures, solvation and helix-coil transitions compete in the individual semiflexible polymers, and the re-entrant phase transitions occur. We also discuss the chain conformation by calculating Kuhn length.