Thermal analysis by differential scanning calorimetry (DSC) was carried out using a TA Instruments Discovery DSC 25. Approximately 10 mg of polymers were placed in sealed aluminum capsules, then analyzed under nitrogen flow (50 mL min -1 ). A three-step procedure with ramps of 10 °C min -1 was applied as follows: (i) heating from 90 °C to 200 °C to erase the thermal history of the samples, (ii) cooling to 90 °C and (iii) heating from 90 °C to 200 °C. Tg values are determined during the second heating step.