Preparation of hydrophobically modified associating multiblock copolymers a one-pot aqueous RAFT polymerization

We describe an efficient strategy for the preparation of hydrophobically associating multiblock copolymers using the RAFT technique. Polymerization reactions were carried out by a one-pot aqueous RAFT polymerization at 70 °C using a symmetrical trithiocarbonate as a chain transfer agent (CTA) in aqueous media. The macroRAFT polyacrylamide (PAM) was synthetized and chain extended by polymerization of N , N ′-dihexylacrylamide (DHAM) and acrylamide (AM), respectively. The resultant polymers were intensely characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, diffusion-ordered spectroscopy (DOSY), Fourier transform-infrared (FT-IR) spectroscopy and rheology. The structure and insertion of a hydrophobic block (PDHAM) into the backbone were carefully demonstrated. The rheological measurements confirmed the effect of the hydrophobic block number on the viscosity of polymers at different concentrations and the formation of a reversible physical network of entangled polymers in aqueous media. Moreover, the incorporation of the hydrophobic block (PDHAM) was established by the oscillatory measurement. A versatile strategy for synthesizing hydrophobically modified associating multiblock copolymers via a one-pot aqueous RAFT polymerization at 70 °C is described. The resultant copolymers exhibited entanglement networks with excellent rheological properties.