聚丙烯酸在硅酸二钙表面吸附的分子动力学模拟

Molecular dynamics simulation of adsorption of polyacrylic acid on surface of dicalcium silicate

采用分子动力学(MD)方法,模拟研究了聚合物抑制剂聚丙烯酸与β-硅酸二钙(110)晶面的相互作用行为.结果表明:聚丙烯酸与β-硅酸二钙(110)晶面间结合能为负值,在模拟范围内结合能随聚丙烯酸聚合度的增加而增大,聚丙烯酸分子能较好地吸附在β-硅酸二钙(110)表面.通过体系中各种相互作用、径向分布函数以及吸附构象图分析,发现聚丙烯酸主要是通过库仑静电作用吸附在β-硅酸二钙(110)晶面上.聚丙烯酸中不同位置羧基的分子动力学模拟结果差别也很大,链端羧基波动扭转比链中端羧基强度大得多,表明中端羧基与β-2Ca O·SiO_2晶体的吸附比链端更牢固,因而更能有效地吸附在晶面上,达到抑制熟料二次反应的作用.

The interactions between polyacrylic acid （PAA） and β-dicalcium silicate （110） crystal face were simulated by molecular dynamics （MD）.The results show that the binding energy for the polyacrylic acid polymer with β-dicalcium silicate （110） crystal is negative and increases with the increasing in the degree of polymerization of polyacrylic acid within simulation range, which indicate that the polyacrylic acid can be adsorbed well on the β-dicalcium silicate crystal face. The analysis of various interactions and pair correlation functions of all systems and adsorption conformation chart indicate that binding energies are mainly determined by coulomb interaction. The results of molecular dynamics simulation of carboxyl groups at different positions of polyacrylic acid also differs greatly. The strength of torsion fluctuation of the chain end carboxyl is larger than that of the mid-chain. Both of those indicate that the mid-chain carboxyl＇s adsorption with β-2CaO·SiO2 crystals is firmer than the chain end carboxyl＇s adsorption with β-2CaO·SiO2 crystals, and more effective. Thus, clinker secondary reaction can be inhibited.