Temperature dependence of a glass transition cooperativity

The size of glass transition cooperativity for 11 polymers and glycerol is determined from heat capacity spectroscopy (HCS) and differential scanning calorimetry (DSC) by using a calorimetric fluctuation formula. The data cover in total the 0.25 ≤ x ≤ 0.95 part of the reduced temperature interval between the Vogel temperature and a cooperativity onset temperature. A steep cooperativity increase at lower temperature is observed. The data are consistent with the hypothesis that the temperature dependence can be described by the enlargement of a minimal cooperativity at the onset.