Synthesis by one-pot RAFT polymerization and properties of amphiphilic pentablock copolymers with repeating blocks of poly(2-hydroxyethyl methacrylate) and poly(butyl methacrylate)

Abstract

One-pot successive three-step RAFT polymerization of 2-hydroxyethyl methacrylate (HEMA) and butyl methacrylate (BMA) in the presence of difunctional RAFT CTA is reported demonstrating successful synthesis of pentablock copolymers containing hydrophilic blocks of pHEMA and hydrophobic blocks of pBMA of low dispersity. Searching for the conditions suitable for high conversion of the monomers, polymerization was carried out in several solvents, including dioxane, butanol, dimethyl formamide, and N-methyl-2-pyrrolidone (NMP). It was shown that NMP was the best solvent enabling to achieve near full monomer conversion during building of the blocks. Effect of the solvents was substantiated by FT-IR and NMR spectroscopy of the monomer solutions.Amphiphilic pentablock copolymers were studied by DSC and contact angle measurements, and their solutions by DLS and 1H NMR spectroscopy. These copolymers showed single glass transition and formed the layers which were more hydrophobic than the layers of pBMA and corresponding diblock copolymers. DMSO was a good solvent for both types of the blocks while chloroform promoted formation of macromolecular associates with hydrophobic corona, and water containing solutions formation of macromolecular associates and larger aggregates with hydrophilic corona.