Tailoring the solution conformation of polycarboxylate superplasticizer toward the improvement of dispersing performance in cement paste

Abstract

Two groups of comb-like polycarboxylate ether (PCE) polymers were synthesized by aqueous free radical polymerization from acrylic acid (AA), methacrylic acid (MAA), and poly(ethylene glycol) monomethyl ether methacrylate. The variation of monomer ratios enabled the tuning of content of methyl group substituted on the polymer backbone and therefore the backbone stiffness and hydrophobicity. As demonstrated by molecular dynamics simulation (COMPASS force field), the solution conformation differences were derived from the backbone methyl group content. PCE containing high backbone methyl group content exhibited a more extended polymer backbone in pore solution due to the hindered free rotation of polymer backbone and more carboxylic groups could be accessible for adsorption. However, the size after adsorption should be smaller possibly due to the hydrophobicity and hindered free rotation of polymer side chain. This paper revealed that the adsorption process was greatly affected with the solution conformation of PCE and offered a new strategy—tailoring the PCE solution conformation, for the tuning of performance of PCE molecules.