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. Copyright © 2008 John Wiley & Sons, Ltd.