Statistical thermodynamics of polyalkane-like chains in a uniaxial environment

We have studied the statistical thermodynamics of polyalkane-like chains in a uniaxial environment, assuming quadrupolar coupling between the monomers and the external field. Using the rotational isomeric state model, we have investigated the temperature, the coupling strength, and the conformational energy dependence of the uniaxial ordering of monomers and chain stretching as well as the entropy and the specific heat of the system. In the case of polymers for which the collapsed conformation is energetically favored over the extended one, we have demonstrated the existence of a "critical" coupling strength at which this tendency is balanced by the stretching influence of the external field and have shown that the system becomes truly critical in the low temperature limit. The relevance of this work to possible experimental situations is also discussed.