ABA block copolymers comprising a water soluble poly(N-hydroxyethyl acrylamide) B block form self-assemblies of varied morphologies in an aqueous environment

Abstract

In this study, we apply a combination of SET-LRP and photoinduced LRP techniques to synthesize novel ABA block copolymers comprising poly(N-hydroxyethyl acrylamide) as a water soluble middle B block, flanked by poly(n-butyl acrylate) A blocks: (n-BA)_m-b-(N-HEA)_n-b-(n-BA)_m. NMR analysis of the copolymers in the ‘best performing’ common solvents indicates the presence of partially solvated poly(n-butyl acrylate) blocks and a well-solvated poly(N-hydroxyethyl acrylamide) block in a DMSO-d₆/acetone-d₆ mixture, whilst the inverse occurs in MeOH-d₄. This partial solvation of the constitutive blocks in the best common solvents may be a contributing factor for the formation of self-assembled structures with varied morphologies and broad particle size distribution on the introduction of a solvent (water) selective for the central poly(N-hydroxyethyl acrylamide) block. With the view of potential biomedical applications, toxicity studies show that the copolymers do not cause appreciable damage to the cell membrane leading to undesirable necrotic cell death, often observed for amphipathic polymeric surfactants, even at relatively high concentrations with 24-hour exposure. We envisage that the middle poly(N-hydroxyethyl acrylamide) block offers the potential to further introduce different surface functionalities, including targeting ligands.