表面活性单体NaAMC14S的胶束化行为对共聚合过程的影响

测定了表面活性单体2-丙烯酰胺基十四烷磺酸钠(NaAMC14S)的Krafft点与不同温度下的临界胶束浓度(cmc), 使NaAMC14S的浓度分别处于cmc上下, 实施了NaAMC14S与丙烯酰胺(AM)的水溶液共聚合. 用复合电导滴定法测定了共聚物的组成, 用差示扫描量热法(DSC)测定了共聚物的热行为, 采用荧光探针芘测定了共聚物水溶液的疏水缔合性, 重点探索了在临界胶束浓度上下NaAMC14S与AM的共聚合机理. 实验结果表明, NaAMC14S的胶束化行为对共聚合过程有很大的影响, 当NaAMC14S在临界胶束浓度以上与AM共聚合时, 遵循的是一种微嵌段共聚合的模式, 聚合过程中共聚物的组成随转化率大幅度地变化；当NaAMC14S在临界胶束浓度以下与AM共聚合时, 进行的是无规共聚合, 聚合过程中聚合物的组成随时间变化比较缓慢; DSC的测试与荧光探针法的测定结果证实了上述机理

Effect of Micellization Behavior of Surface Active Monomer NaAMC14S on Copolymerization Process

The Krafft point and the critical micelle concentrations (cmc) at different temperatures for the surface active monomer, sodium 2-acrylamido-tetradecane (NaAMC14S), were determined. The copolymerizations of NaAMC14S and acrylamide(AM) were carried out in aqueous solution at above and below cmc of NaAMC14S, respectively. The compositions of the copolymers were characterized via conductometric titration method, the thermal behaviors of the copolymers were measured by DSC, and the properties of hydrophobic association of the copolymers were determined by using fluorescence probe technique. By the above investigations, the copolymerization mechanism was explored emphatically. The experiment results show that there are two kinds of copolymerization mechanisms depending on the concentrations of NaAMC14S. When the copolymerization of NaAMC14S and AM is performed above the critical micelle concentration of NaAMC14S, the copolymerization process keeps to be a micro-block copolymerization mechanism, and a large compositional drift occurs during the copolymerization. Whereas when the copolymerization of NaAMC14S and AM is performed below the critical micelle concentration of NaAMC14S, the polymerization process is carried out in agreement with random copolymerization mechanism, and the variation of the copolymer composition with the conversion is slower. The DSC thermograms of the copolymers and the result determined by fluorescence probe technique confirm the above mechanisms.