Zhao Hongxia, Yang Yong, Wang Yanwei, Shu Xin, Wu Shishan, Ran Qianping, Liu Jiaping
State Key Laboratory of High Performance Civil Engineering Materials, Jiangsu Sobute New Materials Co., Ltd., Nanjing, 210008, Jiangsu, China.
School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China.
J Mol Model. 2018 Oct 24;24(11):321. doi: 10.1007/s00894-018-3853-y.
This work investigated interactions between calcium cations (Ca) and three common types of oxygen-based functional groups of concrete superplasticizers using density functional theory (DFT) calculations and all-atom molecular dynamics (MD) simulations. The three common types of oxygen-based functional groups were modeled as three hypothetical, low-molecular-weight organic molecules, each containing a methyl-terminated oxyethylene dimer and an adsorbing head of two oxygen-based functional groups, and are referred to as carboxylate, sulfonate, and phosphate groups, respectively, following the usual terminology in the field of concrete admixtures. Our DFT results show that the binding strength of the three groups with calcium cations follows (from high to low) phosphate>carboxylate>sulfonate, and both the electrophilic attack and the chemical reactivity of the three groups contribute significantly to the binding strength. The MD simulation results indicate that the adsorption of the three small molecules on the calcite (1 0 4) surface in aqueous solution shares a similar pattern in the sense that just two oxygen atoms of two adjacent anchor groups adsorb on the calcium atoms on the top layer of the crystal. The adsorption strength among the three types of functional groups follows the same order as the binding strength obtained from DFT calculations; both results corroborate a similar rule-of-thumb established by experiments. Furthermore, interactions of the three types of groups with water molecules suggest that strong hydrogen-bonding interactions exist in those systems. Graphical abstract Binding of calcium cations with three different types of oxygen-based functional groups of superplasticizersᅟ.
本研究利用密度泛函理论（DFT）计算和全原子分子动力学（MD）模拟，研究了钙阳离子（Ca）与混凝土高效减水剂三种常见类型的氧基官能团之间的相互作用。这三种常见类型的氧基官能团被建模为三种假设的低分子量有机分子，每个分子都含有一个甲基封端的氧乙烯二聚体和一个由两个氧基官能团组成的吸附头，按照混凝土外加剂领域的常用术语，分别称为羧酸盐、磺酸盐和磷酸盐基团。我们的DFT结果表明，这三种基团与钙阳离子的结合强度顺序为（从高到低）磷酸盐>羧酸盐>磺酸盐，并且这三种基团的亲电攻击和化学反应性对结合强度都有显著贡献。MD模拟结果表明，在水溶液中，这三种小分子在方解石（1 0 4）表面的吸附具有相似的模式，即两个相邻锚定基团的仅两个氧原子吸附在晶体顶层的钙原子上。这三种官能团之间的吸附强度遵循与DFT计算得到的结合强度相同的顺序；这两个结果都证实了实验建立的类似经验法则。此外，这三种基团与水分子的相互作用表明，在这些体系中存在强烈的氢键相互作用。图形摘要 钙阳离子与高效减水剂三种不同类型的氧基官能团的结合ᅟ
