2.7. Differential scanning calorimetry (DSC)
Measurements of the film’s glass transition temperature (Tg)
were performed using a differential scanning calorimeter (Shimadzu,
DSC 60). About 2 mg of film samples was placed in a hermetically
sealed aluminum pan and scanned from 100 to 230 C at
10 C/min. An empty pan was used as a reference. Tg was identified
as the midpoint temperature of the shift in the baseline due to the
change in heat capacity upon glass transition. Before the test, samples
were conditioned at 55% RH, 25 C for 48 h.