Effect of molecular weight of Poly(ethylene glycol) on plasticization of Poly(ʟ-lactic acid). (3rd May 2021)

• Record Type: Journal Article
• Authors: Guo, Jianwei; Liu, Xiao; Liu, Ming; Han, Miaomiao; Liu, Yadong; Ji, Shengxiang
• Is Part Of: Polymer. Volume 223(2021)
• Publication Date: 2021-05-03
• Subjects: Polylactide -- Plasticizer -- Nanocrystal -- Phase separation -- α′-to-α transition; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2021.123720
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Poly(ʟ-lactic acid) (PLLA) is a sustainable, biodegradable polymer, but the inherent brittleness impedes its potential application. In this study, we use poly(ethylene glycol) (PEG) to plasticize PLLA and systematically study the effect of molecular weight (MW) and content of PEG on the thermal and mechanical properties of PLLA/PEG blends. We observed a surprisingly big drop of elongation at break ( ε b = 32%) in PLLA/PEG5-15% where PEG5-15% represents 15 wt% of PEG with the MW of 5 kg/mol while ε b s of PLLA/PEG-15% where PEG-15% represents 15 wt% of PEG with other MW PEGs were ~300%. WAXD results confirmed that PLLA in quenched PLLA/PEG-15% blends crystallized into mixtures of α′-form and α-form crystals during heating. DSC analysis showed that two cold crystallization temperature ( T cc s) were observed in PLLA/PEG5-15% while only one T cc was observed in PLLA/PEG2-15% and PLLA/PEG8-15%, indicating that PLLA/PEG5-15% formed separated α′-form and α-form crystals while the other two blends formed mixed α′-form and α-form crystals. The competition between phase separation and PLLA crystallization determined the final structures and physical properties of PLLA/PEG blends. Graphical abstract: Image 1 Highlights: The elongation at break of PLLA/PEG5-15% was only 1/10 of PLLA/PEG-15% with other molecular weight PEGs. Two cold crystallization peaks, corresponding to α and α′ crystal forms, were observed in PLLA/PEG5-15%. PLLA/PEG5 was more prone to phase separation than PLLA/PEG blends with other molecular weight PEGs. The plasticizing mechanism was revealed for PLLA/PEG blends with different molecular weight PEGs.