Understanding the influence of chemical structure and length of hydrophobic blocks on the rheological properties of associative copolymers

•HAWSPs were prepared via a surfactant free, aqueous and sequential RAFT polymerization.•The number of the hydrophobic segments within a main hydrophilic block affected polymer entanglement.•Chemical structure of the hydrophobic segments has an influence on rheological properties.•Size of formed nanoparticles depends on the structure of the hydrophobic segments.•Viscosity of HAWSPs aqueous solutions can reach values of ca. 100 Pa.s. [Display omitted] Structure-property relationships of hydrophobic associative water soluble (co)polymers (HAWSPs) were investigated. Different HAWSPs were prepared using a polyacrylamide precursor synthesized by a reversible addition-fragmentation chain transfer polymerization process (macroRAFT-PAM). Subsequently, several chain extension polymerization reactions were performed in a one-pot process by sequentially incorporating N,N'-diphenylacrylamide (DPAM), N'-dodecylacrylamide (DDAM) or dodecyl acrylate (DDA) into the macroRAFT-PAM to systematically prepare different series of multi-block copolymer materials. The utilized acrylamido monomers, DPAM and DDAM, were synthesized and characterized by Nuclear Magnetic Resonance (1H and 13C NMR) and X-Ray Diffraction (XRD). Moreover, Size Exclusion Chromatography (SEC), Diffusion Ordered Spectroscopy (DOSY), Dynamic Light Scattering (DLS) and Transmission Electronic Microscope (TEM) investigations performed on the obtained HAWSPs corroborated the successful insertion of the hydrophobic monomeric units throughout the polymeric chains of the different HAWSPs multi-block copolymers. These investigations also allowed evaluating the influence of the chemical structure and the length of the hydrophobic blocks on the properties of the synthetized HAWSPs. Rheological measurements of different HAWSPs aqueous dispersions at different concentrations demonstrated the effect of the hydrophobic blocks on the formation of chain entanglements and thickening properties of the investigated HAWSPs, which may represent interesting candidates for preparing fracturing fluids in enhanced oil recovery (EOR) applications.