Differential scanning calorimetry (DSC) tests were used to determine glass transition temperatures (Tg) of all materials using a TA DSC Q-2000 instrument (New Castle, DE, USA) under nitrogen
atmosphere (flow rate 50 mL min1). 3 mg samples were heated from 30 to 200 C at 10C min1 (3 min hold), then cooled at 10 C min1 to 30 C (3 min hold) and further heating to 200 C at 10 C min1