The DSC thermogram (equilibrated with an indium standard; each sample weighed 3–5 mg) was obtained during the heating from 25 to 350 ◦C at a heating rate of 10 ◦Cmin−1 under nitrogen purge (60 ml min−1), while the TGA thermogram was obtained during the heating from 30 to 600 ◦C at a rate of 10 ◦Cmin−1 under nitrogen purge (200 ml min−1)