疏水改性聚丙烯酰胺溶液的分子模拟

Molecular Simulation Study on Hydrophobically Modified Polyacrylamide Solutions

设计了几种不同的非离子型改性聚丙烯酰胺(HM-PAM)和阴离子型改性聚丙烯酰胺(HM-HPAM).通过分子动力学模拟(MD)方法研究了在聚合物链上加入不同疏水改性单体对提高聚丙烯酰胺耐盐性的影响,考察了盐浓度对疏水改性聚丙烯酰胺的回旋半径(Rg)、特性黏数([η])、径向分布函数(RDF)和均方位移(MSD)的影响以及聚合物的微观结构与特性黏数之间的关系.研究结果表明,引入疏水改性单体后,改性聚丙烯酰胺具有较好的耐盐性.通过研究非键作用与氢键相互作用可知,体系中溶质和溶剂间的相互作用及氢键作用越弱,溶液的特性黏数越大.O—H原子对的RDF结果表明,聚合物链的伸展与聚合物链及官能团间的相互作用有关.当RDF峰较弱时,聚合物链与水的作用越弱,越有利于聚合物链保持舒展状态,溶液的特性黏数也就越大.另外,从聚合物链的MSD曲线发现,聚合链的移动性与特性黏数呈负相关.

Several types of hydrophobically modified polyacrylamide chains （HM-PAM） and hydrophobically modified of partially hydrolytic polyacrylamide （HM-HPAM） were designed. The influence of hydrophobic monomers on the property of salt-resistance of polyacrylamide was studied using molecular dynamics （MD） simulation. The characteristics of the HM-PAM and HM-HPAM [ Such as the radius of gyration（Rg ）, intrinsic viscosity（ [ η] ）, radial distribution function（RDF） and mean square displacement（MSD） ] were studied as well as the relationship between the microstructure of the polymer chain and its intrinsic viscosity. It was shown that the addition of hydrophobic monomers to the polymer chain improved the property of salt-resistance of polyaerylamide. Furthermore, the intrinsic viscosity of the solution increased with the decreasing of nonbonding interaction and hydrogen bonding interaction. The RDF of O-H atomic pairs showed the relationship between the microstructure of the polymer chain and the intrinsic viscosity. The interaction between the polymer chain and water molecules is stronger when the peak of RDF is lower, and the polymer chain can remain stretched so that the intrinsic viscosity of the solution is larger. The curves of MSD exhibited inverse linear relation with the polymer chain mobility and intrinsic viscosity of the solution.