【摘要】 采用恒流滴定法，以高效液相色谱跟踪聚丙烯酸（PAA）水溶液聚合反应过程，系统研究了单体浓度、体系pH、链转移剂量、加料时间、引发剂量及反应温度等对PAA分子量的影响，获得了低分子量PAA的可控合成方法。以所制的PAA为超分散剂，利用正交试验研究了pH、PAA分子量及其质量分数等因素对纳米二氧化硅颗粒分散性能的影响。研究结果表明：单体丙烯酸浓度不宜过大，控制在小于30%为宜；若要获得低分子聚合物，单体pH应该小于4.5；随着链转移剂异丙醇量的增加，PAA分子量下降，当异丙醇/丙烯酸质量比为2.9∶1时，PAA分子量降为3 000左右；随着加料时间的延长，PAA分子量逐渐下降并趋缓，综合考虑，加料时间控制在120 min为宜；随着引发剂量增大或反应温度增加，PAA的动力学链长减小，分子量相应减小。多因素方差分析表明，pH对分散效果影响最大。同时确定了纳米二氧化硅的最优分散条件为：pH为7,PAA分子量为5 210，质量分数为2.0%。更多还原

【Abstract】 The polymerization process of polyacrylic acid(PAA) aqueous solution was tracked by highperformance liquid chromatography with the constant current titration method. The effects of monomer concentration,system pH value,chain transfer agent amount,feeding time,initiator amount and reaction temperature on the molecular weight of PAA were systematically studied,and the controllable synthesis method for low molecular weight PAA was obtained.The effects of pH value,PAA molecular weight,and its mass fraction on the dispersion performance of nano silica particles were studied by orthogonal experiment with the prepared PAA as hyperdispersant.The research results showed that the concentration of monomer acrylic acid should not be too high and should be controlled at less than 30%.In order to obtain low molecular weight polymer,the monomer pH value should be less than 4.5.As the amount of chain transfer agent isopropanol increased,the molecular weight of PAA decreased.When the mass ratio of isopropanol to acrylic acid was 2.9∶1,the molecular weight of PAA decreased to about 3 000.As the feeding time prolonged,the molecular weight of PAA gradually decreased and slowed down.Overall,it was advisable to control the feeding time at 120 minutes.As the initiator amount or reaction temperature increased,the kinetic chain length of PAA decreased,and the molecular weight correspondingly decreased.Multivariate analysis of variance showed that pH value had the greatest impact on dispersion effect.The optimal dispersion conditions for nano silica were determined as follows:the pH value was 7,the molecular weight of PAA was 5 210,and the mass fraction was 2.0%.更多还原