Molecular dynamics simulation on the interaction mechanism between polymer inhibitors and calcium phosphate

Abstract

Investigation on the microscopic interaction between polymer inhibitors and calcium phosphate contributes to the understanding of their scale inhibition mechanism. The results obtained may provide a theoretical guidance to developing new scale inhibitors. In this study, molecular dynamics simulations have been performed to simulate the interaction between hydrolyzed polymaleic anhydride (HPMA), polyaspartic acid (PASP), polyepoxysuccinic acid (PESA), polyacrylic acid (PAA) and the (001) and (110) surfaces of hydroxyapatite (HA) crystal with and without water. Results show that the simulations of polymer inhibitors and the (001) surface of HA with water is closer to the actual situation. On the same HA (001), binding energy of four polymer inhibitors with water has the order of HPMA > PASP > PESA> PAA. On the different surface of HA, the binding energy does not vary much between the same polymer and the two surfaces of HA. But, deformation energies of the same polymer with and without water vary widely. Pair correlation function of Ca (HA)-O (-C=O) implies that the Ca-O bonds formed between the calcium atoms of HA crystal and oxygen atoms of the carboxyl groups in polymers, and water molecules change the distances between polymer inhibitors and HA crystal. The system of polymer-HA is mainly contributed by the non-bond interaction. Polymer inhibitors do not interact directly with HA crystal, but indirectly through the interactions between inhibitor–H2O and H2O–HA. Water molecules cannot be ignored when the interaction models are constructed, i.e., solvent effect must be considered.