Glass transition temperature and molecular parameters of polymer

Abstract

A new relationship, which correlates the glass transition temperature ( T g) with other molecular parameters, is developed by using Flory's lattice statistics of polymer chain and taking the dynamic segment as the basic statistical unit. The dependences of T g on the chain stiffness factor ( σ 2), dynamic stiffness factor ( β = − d ln σ 2 dT ) and molecular weight of polymer are discussed in detail based on the theory. The theory is compared with experimental data for many linear polymers and good agreement is obtained. It is shown that T g is essentially governed by the chain stiffness factor at T g. Moreover, a simple correlation between the parameter K g of the Fox-Flory equation ( T g = T ∞ g − K g M n ) and other molecular parameters is deduced. The agreement between theoretical predictions and experimental measurements of K g has been found to be satisfactory for many polymers.