Melting and recrystallization behaviour of PVCH-PE-PVCH triblock copolymer in supercritical CO ₂

The melting and recrystallization behaviour of poly (vinylcyclohexane)-b-poly (ethylene)-b-poly (vinylcyclohexane) (PVCH-PE-PVCH) triblock copolymer in supercritical carbon dioxide (CO ₂) was investigated by using of DSC. The effect of the rate of the depressurization of CO ₂ on the crystallization of the samples was also examined. It is found that there are three melting peaks on each DSC curve of the samples treated in supercritical CO ₂ at the temperature above t _m of the untreated PVCH-PE-PVCH. They corresponded to the 'hard' confined crystallization of PE blocks homogeneous nucleation, the 'soft' confined crystallization of PE blocks homogeneous nucleation and the self-seeding nucleation free crystallization of PE blocks respectively. Furthermore, these three kinds of crystallization could be controlled by changing the competition between the crystallization of PE block and the vitrifaction of PVCH block in the samples, which depended on the rate of the depressurization of CO ₂.