MOLECULAR DYNAMICS SIMULATION THE HYDROXYAPATITE SCALE INHIBITION MECHANISM OF WATER-SOLUBLE POLYMERS

Abstract

Molecular dynamics (MD) method was used to simulate the interaction between water-soluble polymers, such as polyacrylic acid (PAA), polymethylacrylic acid (PMAA), acrylic acid-methylacrylate copolymer (AA-MAE), acrylic acid-hydroxypropyl acrylate copolymer (AA-HPA), hydrolyzed polymaleic anhydride (HPMA), acrylic acid-maleic acid copolymer (AA-MA), and hydroxyapatite crystal. The sequence of binding energies of polymers binding with the (100) crystal surface of hydroxyapatite was as follows: AA-HPA > AA-MA > HPMA > PAA > AA-MAE > PMAA. After analyzing various energy components and pair correlation functions of all systems, it could be concluded that binding energies were mainly determined by Coulomb interaction. Polymers deformed during their combining with the hydroxyapatite crystal, but all the deformation energies were far less than respective nonbond energies. The dynamics behavior of carboxyls located at different positions of the polymer chains manifested different features during the processes of MD runs. Carboxyls at the ends of the polymer chains oscillated more acutely than those in the middle of the chains; therefore, the latter ones inhibited scale crystal growth more effectively than the former ones because they combined with hydroxyapatite crystal more firmly.