Synthesis and characterization of amphiphilic graft copolymers with poly(ethylene glycol) as the hydrophilic backbone and poly(butyl methacrylate) as the hydrophobic graft chain

A series of amphiphilic graft copolymers with hydrophilic polyethylene glycol (PEG) backbone and different densities of hydrophobic poly(butyl methacrylate) (PBMA) side chains were synthesized via a strategy combining polycondensation and through activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) technology. The hydrophilic macro-ATRP initiators having different amounts of active side bromo atoms were first synthesized by reacting the small ATRP initiator which contains two hydroxyl groups with hexamethylene diisocyanate (HDI) and polyethylene glycol (PEG1000). By graft from technology, the amphiphilic graft copolymers were then synthesized via ARGET ATRP of butyl methacrylate (BMA) using the hydrophilic macro-ATRP initiators. The steric shield effects of the macro-initiator lowered the polymerization rate and final conversion of BMA. The amphiphilic graft copolymers in aqueous media had critical micelle concentration (CMC) in the range of 10⁻⁶ to 10⁻⁷ g/mL, which were determined by fluorescence method using pyrene as a probe. The aggregate sizes of the amphiphilic graft copolymers in different solvents changed greatly, which were due to different interactions between the amphiphilic graft copolymers and the solvents and the incompatibility between PEG and PBMA segments.