Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

The crystallization activation energy (Delta E) of a polymer comprises the nucleation activation energy Delta F and the transport activation energy Delta E-star. In this paper, the Delta E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p-tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Delta E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Delta E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature (Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Delta E-star. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Delta E-star caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Delta F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Delta E for PLLA/tBC8.