Synthesis and Characterization of Amphiphilic Biodegradable Hyperbranched-linear-hyperbranched Copolymers Based on PEG, PLA, and BHP

Abstract

A series of biodegradable multifunctional hyperbranched-linear-hyperbranched copolymers (HLHCs) were prepared by poly(ethylene glycol), D,L-lactic acid, and 2,2-Bis(hydroxymethyl)propionic acid (BHP) under bulk condition. The degree of branching of the hyperbranched section was varied by controlling the molar ratio of BHP to hydroxyl-terminal groups of PEG ([BHP]/[OH] = 1, 3, 7, 15). Chemical structure of the copolymers was confirmed by both 1H-NMR and 13C-NMR spectroscopy. The molecular weights were determined by 1H-NMR end-group analysis and gel permeation chromatography, respectively. The resulting copolymers were subsequently characterized via atomic force microscopy, which was utilized in this research to investigate the Langmuir-Blodgett films morphology and the structure of barbell-like copolymers.

Keywords:

• amphiphilic
• biodegradable polymers
• direct polycondensation
• hyperbranched-linear-hyperbranched

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (No. 20174031 and 20474052). We also thank Key Basic Research Pre-projects (2007CCA06000), Ministry of Science and Technology of China, and Key Laboratory of Eco-Environment-Related Polymer Materials (Northwest Normal University), Ministry of Education, for financial support.

Notes

^a According to the definition of Frey et al. [14].

^b Theoretic average molecular weights were calculated with feed ratio of materials, a sum of PEG, PLA, and BHP and the branched ester linkages.

^c Molecular weights were evaluated by ¹H-NMR.

^d,e Molecular weights were determined by GPC with polystyrene standards.