Synthesis of poly(ethylene glycol)-b-poly(mercapto ethylacrylamide) diblock copolymer via atom transfer radical polymerization

Abstract

Atom transfer radical polymerization was used to synthesize a well-defined poly(ethylene glycol)-b-poly(mercapto ethylacrylamide) (PEG-b-PMEAAm) diblock copolymer. Poly(ethylene glycol)-b-poly[N-(acryloxysuccinimide)](PEG-b-PNAS) was synthesized at 80 °C using methoxy-poly(ethylene glycol)-2-bromo propanoate (PEG-Br) and CuBr/2,2′-bipyridine as a macroinitiator and catalyst, respectively. The monomer conversion was determined by 1H nuclear magnetic resonance (NMR) spectroscopy. The resulting PEG-b-PNAS diblock copolymer was characterized by gel permeation chromatography, Fourier transform infrared (FT-IR), and 1H NMR spectroscopy. Disulfide groups were introduced by a simple reaction through the N-acryloxysuccinimide (NAS) moieties of the PEG-b-PNAS diblock copolymer with cystamine dihydrochloride in the presence of triethylamine. FT-IR spectroscopy was used to confirm the introduction of disulfide moieties into the polymer repeating units. Subsequently, a thiol-functionalized block copolymer was prepared using DL-dithiothreitol (DTT) as the reducing agent and the reduction step was monitored by 1H NMR spectroscopy. This thiol group was transformed easily to a disulfide bond using FeCl3 as an oxidizing agent. The transformation into disulfide could be visualized easily as insoluble polymeric particles formed from a clear solution of PEG-b-PMEAAm after oxidation.