Nonisothermal Crystallization Behavior and Crystallization Morphology of Three‐Arm Polylactic Acid With Different Chain Lengths

ABSTRACT To investigate the effects of chain length on the crystallization ability of three‐arm polylactic acid (TA‐PLA), a series of TA‐PLA samples with different chain lengths were synthesized by ring‐opening polymerization of lactide. Differential scanning calorimetry (DSC) was used to study their nonisothermal crystallization behavior, and the polarized optical microscope (POM) was used to observe their isothermal crystallization morphology. The analysis revealed that the increase in chain length reduced the crystallization ability of TA‐PLA. For instance, TA‐PLA 12.1 with the longest chain length only exhibited a crystallinity of 38.21% at a cooling rate of 1°C/min, whereas TA‐PLA 3.9 reached a crystallinity of up to 70.75%. The Mo equation provided an accurate description of nonisothermal crystallization kinetics and was shown to simulate the process of TA‐PLA sample crystallization successfully. From the photographs captured using POM, it was evident that the long chains slowed the growth rate (G) of spherical crystals of TA‐PLA samples. Furthermore, samples with different chain lengths exhibited distinct temperature dependencies in their spherulitic growth rates.