阳离子对聚合物溶液黏度损失的影响机制

研究Na^+、Ca^2+、Mg^2+等阳离子对聚合物溶液黏度的影响机制,考察不同离子质量浓度对聚合物溶液黏度的影响,利用扫描电镜对聚合物微观形貌进行分析,利用凝胶色谱-示差折光检测器对聚合物相对分子质量进行检测,采用分子动力学模拟研究阳离子对聚合物分子构型的影响。结果表明:Na^+质量浓度高于5 g/L、Ca^2+和Mg^2+质量浓度高于0.4 g/L,聚合物黏度损失超过70%;外加阳离子条件下,聚合物相对分子质量变化不大,但均方回转半径降低;阳离子导致聚合物溶液黏度降低的主要原因是阳离子与聚合物分子链内的带负电基团的静电吸引作用造成对聚合物分子链的压缩,从而使聚合物分子链卷曲、收缩。

Mechanism of cation on viscosity loss of polyacrylamide solution

The influence mechanism of Na^+,Ca^2+,and Mg^2+on the viscosity loss of polymer solution was investigated.The effects of different ion concentrations on the viscosity of polymer solution were studied.Scanning electron microscopy was used to analyze the polymer microstructure.Gel chromatography-refractive index detector was used to determine the polymer molecular weight.And molecular dynamics simulation was employed to reveal the influence of cation on the polymer molecular configuration.It is found that the polymer viscosity loss is more than 70%when the concentrations of Na^+,Ca^2+,Mg^2+are above 5g/L,0.4g/L and 0.4g/L,respectively.Under the condition of external cation,the molecular weight of polymer does not change significantly.However,the mean-square radius of gyration is reduced.The main reason of viscosity loss by the cation was the electrostatic attraction between cation and negatively charged groups of polymer molecule chains,which causes compression of polymer molecular chain.The coil and shrinkage of polymer molecular chain lead to the breakage of the spatial network structure of macromolecules.