Molecular thermodynamic model of the glass transition temperature: Dependence on molecular weight

A new molecular thermodynamic model to predict the dependency of the glass transition temperature (T_g) of polymer on its molecular weight was developed based on the configurational entropy model and the Flory-Huggins theory. In this model, the disorientation entropy of the polymer (S_dis) has been taken into account. Quantitative descriptions according to the proposed model are consistent with experimental T_g data of several polymers against the number of chain segment (r). At the same T_g.∞ (T_g of polymer at a infinite r value), the degree of polymer disorientation is strongly correlated with the slope of straight line at lower r regions in the T_g versus r plot, which is quantitatively identified by physical parameter (γ_dis) in this model.