Synthesis and characterization of methacrylate-type hyperbranched glycopolymers via self-condensing atom transfer radical copolymerization

We report the synthesis of hyperbranched glycopolymers by self-condensing vinyl copolymerization (SCVCP) of the methacrylic AB* inimer 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) with 3-O-methacryloyl-1,2:5,6-di-O-isopropylidene-alpha-D-glueofuranose (MAIGlc) via atom transfer radical polymerization, followed by deprotection of the isopropylidene protecting groups. Homopolymerization of MAIGlc with the (PPh3)(2)NiBr2 catalyst system in solution proceeds smoothly, resulting in linear poly(MAIGlc) having controlled molecular weights and narrow molecular weight distribution. The catalyst system could be applied for SCVCP to synthesize hyperbranched poly(MAIGlc)s, as confirmed by GPC and GPC/viscosity analyses and H-1, C-13, and 2D NMR measurements. Depending on the comonomer ratio, gamma = [MAIGlc](0)/[BIEM](0), branched poly(MAIGlc)s with number-average molecular weights between 17500 and 29800 and Mark-Houwink exponents between 0.20 and 0.34 were obtained within reasonable polymerization time (4 h), the polymerization being very much faster than that of the corresponding glycopolyacrylates. Deprotection of the isopropylidene protecting groups of the branched poly(MAIGlc)s resulted in water-soluble glycopolymers with randomly branched architectures, which were characterized by elemental analyses and H-1 NMR and FT-IR measurements.