The effect of degree of polymerization on glass‐transition temperatures

Finite‐molecular‐mass homopolymers are modeled as binary random mixtures of high polymers and oligomers or chain ends, in proportions determined by the number‐average degree of polymerization. This leads directly to an entropic equation for the effect of molecular mass on Tq in terms of the glass‐transition temperatures and transition increments of heat capacity of these two components. Predictions of the theory are found to be in satisfactory agreement with calorimetric measurements of Tg over a wide range of molecular mass.