Synthesis of brush-like copolymers using carbohydrates as initiators: Benefits of organic catalysts for the ROP of lactones

Abstract

New brush-like copolymers have been synthesized using functional polymethacrylate backbones bearing pendant sugars. Ring-opening polymerization (ROP) of l-lactide and ε-caprolactone have been performed using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) carbohydrate residues on the polymethacrylate chains. The latter have been first synthesized by copolymerization of three methacrylate monomers including methyl methacrylate (MMA), α-methoxy, ω-methacrylate poly(ethylene oxide) (MAPEO), and 1,2:3,4-di-O-isopropylidene-6-O-methacryloyl- d-galactopyranose (MAIGP) by atom transfer radical polymerization (ATRP) in toluene at 80 °C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. The protected sugars have been selectively deprotected using an aqueous solution of formic acid. The molecular characterization of those copolymers was performed by 1H-NMR spectroscopy, FT-IR spectroscopy and gel permeation chromatography (GPC) analysis.