Molecular Chain Flexibility and Phase Transitions in Polymers

Abstract

The effects linked to the transformation of thermal energy absorbed by a compound into internal rotational energy are analyzed through the CSD (Conformations Statistical Distribution) method.

The application of statistical mechanics to the allowed conformational microstates belonging to the rotational hypersurface of a molecule leads to the calculation of partition function, entropy and thermodynamic potentials of the molecular system. Conformational transitions versus temperature can then be pointed out for representative models of molecular flexible chains and correlated to phase transitions in the corresponding polymeric materials. Other physical quantities such as steric and electronic features affecting packing between molecules are studied for the models and their variations with temperature are calculated in the transition range.

Examples are given of the correspondence between calculated spectra for single polymeric chain models and experimental transition temperatures or DSC curves of some known polymers and thermotropic liquid-crystal polymers.