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

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.