TEMPERATURE-DEPENDENCE OF ALPHA-GLASS-TRANSITION COOPERATIVITY

The size of glass transition cooperativity for 11 polymers and glycero l is determined from heat capacity spectroscopy (HCS) and differential scanning calorimetry (DSC) by using a calorimetric fluctuation formul a. The data cover in total the 0.25 less than or equal to x less than or equal to 0.95 part of the reduced temperature interval between the Vogel temperature and a cooperativity onset temperature. A steep coope rativity increase at lower temperature is observed. The data are consi stent with the hypothesis that the temperature dependence can be descr ibed by the enlargement of a minimal cooperativity at the onset.