Crystallization behavior of stereoblock polylactide with high sequence regularity structure

• Published in: Polymers for advanced technologies Vol. 33; no. 12; pp. 4381 - 4390
• Main Authors: Wuyou, Ye, Qi, Xia, Dongyang, Liu, Shida, Gao, Zhongyong, Fan, Qing, Liu
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.12.2022; Wiley Subscription Services, Inc
• Subjects: Crystal structure; Crystallization; Free energy; Melting points; Molecular structure; NMR; Nuclear magnetic resonance; Nucleation; nucleation parameters; Optical microscopy; Polylactic acid; Polylactide; Ring opening polymerization; sequence structure; stereocomplex crystallization
• ISSN: 1042-7147; 1099-1581
• DOI: 10.1002/pat.5867

Stereoblock polylactide (Sb‐PLA) was prepared via a consecutive method by ring‐opening polymerization and its stereocomplex crystallization behavior was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM). The molecular weight, sequence structure of anisotropic segments of Sb‐PLA and crystals structure were characterized by using GPC, 1H NMR, 13C NMR and XRD. The Sb‐PLA with bonding a higher stereoregularity chains prepared by the synthesis route exhibited a higher melting point and uniquely stereocomplex crystallization behavior compared with the Sb‐PLA prepared by commonly reported method. The isothermal crystallization results indicated that the crystallization temperature of Sb‐PLA's increased about 20°C higher than reported Sc‐PLA materials. Moreover, crystallization rate constant (K) and crystallization activation energy (ΔE) expressed by the Arrhenius equation demonstrated that Sb‐PLA presents a higher crystallization rate. The data of isothermal crystallization experiments were analyzed based on Lauritzen–Hoffman (LH) theory, crystallization rate constant (G0), nucleation constant (Kg), fold surface free energy (σe), and folding work (q) were estimated to be 1.5 × 1027 μm/min, 1.2 × 106 K2, 113.0 erg/cm2 and 8.20 × 10−21 J, respectively. These results indicated that Sb‐PLA chains with a higher stereoregularity suggested to be the main factor accounting for the formation unique stereocomplex crystals.