Carbohydrate-based amphiphilic diblock copolymers: Synthesis, characterization, and aqueous properties

Amphophilic poly(ε-caprolactone)-b-poly[(methacrylate-graft- poly(ethylene oxide))-co-6-O-methacryloyl-D-galactopyranose] (PCL-b-P(MAPEO-co-GaMa)) with various compositions and molecular weights were synthesized via a controlled four-step strategy. The first step involves the synthesis of functionalized poly(ε-caprolactone) macroinitiator by ring-opening polymerization (ROP) of ε-caprolactone (CL) as initiated by aluminum triisopropoxide (Al(OⁱPr)₃). After selective bromination of the hydroxyl end-group of the resulting α-isopropoxy, ω-hydroxy poly(ε-caprolactone) by using 2-bromoisobutyryl bromide, the controlled radical copolymerization of α-methoxy, ω-methacrylate poly(ethylene oxide) (MAPEO) with 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene- D-galactopyranose (DIGaMa) was performed by atom transfer radical polymerization (ATRP) in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. In the final step, isopropylidene protective functions were selectively removed using an aqueous formic acid solution leading to the expected amphiphilic graft copolymers. The molecular characterization of those copolymers was performed by ¹H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self-assembly of the copolymers into micellar aggregates as well as the related critical micellization concentration (CMC) in aqueous media were determined by dynamic light scattering (DLS) and fluorescence spectroscopy, respectively. In parallel, the morphology of the solid deposits of micellar aggregates was examined with atomic force microscopy (AFM).