Differential scanning calorimeter (DSC) measurement was performed using a TA Instruments Q200 analyzer. DSC analysis was carried out under a flow of nitrogen (sample purge flow: N2 40 mL/min.) The sample was sealed in a fume hood using TA Instruments Tzero hermetic aluminum pan and four heating/cooling cycles were performed from 293.15 to 593.15 K in 10 K/min rate.