The confined crystallization of poly(??caprolactone) (PCL) block in poly(??caprolactone)?poly(L?lactide) (PCL?PLLA) copolymers were investigated by differential scanning calorimetry, polarized optical microscope, scanning electronic microscopy and atomic force microscopy. To study the effect of crystallization and molecular chain motion state of PLLA blocks in PCL?PLLA copolymers on PCL crystallization morphology, the high temperature annealing (180 ?C) and low temperature annealing (80 ?C) were applied to treat the samples. It was found that the crystallization morphology of PCL block in PCL?PLLA copolymers is not only related to the block ratio of block components, but also related to the thermal history. After PCL?PLLA copolymers annealed at 180 ?C, the molten PCL blocks are rejected from the front of PLLA crystal growth into the amorphous regions, which will lead to PCL and PLLA blocks occur obvious fractionated crystallization and form various morphologies depending on the length of PLLA segment. On the contrary, PCL blocks are easier to form banded spherulites after PCL?PLLA copolymers annealed at 80 ?C because the preexisting PLLA crystal template and the dangling amorphous PLLA chains on PCL segments are easier to cause unequal stresses at opposite fold surfaces of PCL lamellar during growth process. Besides, it was also found that the growth rate of banded spherulites is smaller than that of the classical spherulites and the growth rate of banded spherulites decreases with decreasing the band spacing.This article is protected by copyright. All rights reserved.

» Author: Weiqiang Han, Shaojie Li, Xia Liao, Bin He, Qi Yang, Guangxian Li

» Reference: doi:10.1002/pi.5911

» Publication Date: 24/08/2019

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