Direct polycondensation of l-lactic acid in hydrophobic bis(trifluoromethanesulfonyl)imide-anionic ionic liquids: A kinetic study. (5th September 2021)

• Record Type: Journal Article
• Authors: Peng, Qiaohong; Wei, Li; Zhang, Xiaoyan; Wu, Ying; Mahmood, Khalid; Liu, Zhengping; Zhang, Lisha
• Is Part Of: European polymer journal. Volume 158(2021)
• Publication Date: 2021-09-05
• Subjects: Hydrophobic ionic liquids -- Polycondensation kinetics -- Bio-based polymer -- Poly(lactic acid) -- Hildebrand solubility parameter; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2021.110692
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Bio-based poly(l -lactic acid) with molecular weight as high as 132 kDa was synthesized by solution polycondensation of l -lactic acid in hydrophobic bis(trifluoromethanesulfonyl)imide-anionic ionic liquids. The effects of the solvent property and structure of the ionic liquids on the direct polycondensation of l -lactic acid were investigated comprehensively. Highlights: High molecular weight PLLA was synthesized by solution polycondensation of LLA in ILs. Both solubility parameter and structure of IL have impact on the polycondensations. Kinetics of the solution polycondensations demonstrates the acceleration effect of IL. Lactide does not show significant influence on the polycondensations in ILs. Abstract: Ionic liquids (ILs), instead of the classical organic solvents, have shown great improvements in chemical processes. Herein, Water-insoluble alkyl- and benzyl-substituted imidazolium bis(trifluoromethanesulfonyl)imides as non-volatile and thermostable solvents were employed in the direct polycondensation of l -lactic acid (LLA). The effects of monomer concentration, reaction temperature and miscibility between the ILs and poly(l -lactic acid) (PLLA) were comprehensively investigated. Biodegradable PLLA with weight-average molecular weight as high as 132 kDa was synthesized. Compared to melt-polycondensation of LLA, far higher molecular weight could be achieved via the solution polycondensation of LLA in ILs since the viscosity of the polymer melt could be significantly reduced based on the dilution effect of ILs. Polycondensation kinetics of LLA in bulk and in an IL demonstrated that the IL could accelerate the polycondensation of LLA. Influence of lactide, the main by-product, on the polycondensations of LLA was also studied kinetically.