Effect of counter-ions on the solution conformation and adsorption behaviors of comb-like polycarboxylates on calcium carbonate

Abstract

Three kinds of polycarboxylate ether (PCE) polymers with the same length of side chains but different backbone length were synthesized by aqueous free radical polymerization. Adding counter-ions (i.e., Na+, Ca2+) to dilute PCE solutions was found to induce a more complicated conformational change, since the screening of the electrostatic intramolecular repulsion and the different complexation behaviors of Ca2+ with carboxylic groups. Further characterization on the adsorption indicated that the differences of the adsorption ability resulted from the difference in the solution conformation of PCE molecule. PCE of a medium backbone length studied herein possesses a more extended polymer backbone due to the intermolecular steric hindrance, which result in more carboxylic groups could be accessible for adsorption. Obviously, the solution conformation of PCE strongly impacts the accessible carboxylic group contribution to adsorption. In this way it may provide a new insight to design the polymer structures of PCE with superior adsorption ability.