粒径可控阳离子型聚苯乙烯纳米粒子的制备及表征

在采用阳离子型双子（gemini）表面活性剂作为乳化剂，不使用任何助乳化剂的条件下，通过改进微乳液聚合工艺制备了窄分布粒径可控的阳离子型聚苯乙烯（PS）纳米乳液。 改进微乳液聚合的主要特点是：大部分苯乙烯以预乳液的形式恒速滴入引发聚合的微乳液中，使用具有高乳化性能的gemini表面活性剂作为乳化剂能明显降低乳胶粒粒径。 实验结果表明，少量阳离子单体三甲基烯丙基氯化铵作为共聚单体能够明显减小Z均粒径、降低粒度分布，乳化剂用量、引发剂用量和反应温度均能影响制备乳胶粒的粒径及其粒度分布。 乳化剂和引发剂用量分别为苯乙烯质量的5%~10%和1.0%~1.5%、反应温度为70~75 ℃时，能够制备粒径小分布窄的阳离子型聚苯乙烯纳米粒子。 Z均粒径与苯乙烯质量之间的线性关系表明，Z均粒径可以通过苯乙烯用量来控制。 不同聚合工艺下制备的聚合物粒度分布曲线表明，改进微乳液聚合工艺（半连续预乳化工艺）在制备窄分布的聚合物纳米粒子方面具有很强的优越性。

Synthesis and Characterization of Size Controllable Cationic Polystyrene Nanoparticles

Narrowly distributed and size controllable cationic polystyrene(PS) nanoemulsions were prepared through modified microemulsion polymerization with a cationic gemini surfactant as emulsifier without using any cosurfactants.The main feature of the modified microemulsion polymerization is that most of the styrene in the form of preemulsion is post-added gradually into the initiated microemulsion,and the cationic gemini surfactant with high emulsifying property is employed to decrease particle size.The results show that a small amount of trimethylallylammonium chloride used as comonomer can reduce Z-average particle size and size distribution.Emulsifier content,initiator content and reaction temperature can affect particle size and size distribution of obtained colloid particles.The best experimental conditions for preparing the cationic polystyrene nanoparticles with small particle size as well as narrow size distribution are emulsifier content(the mass ratio versus styrene(St) at 5%~10%,initiator content at 1.0%~1.5%,reaction temperature at 70~75 ℃.The linear relationship between the Z-average particle size and St feeding amount demonstrates that Z-average particle size can be controlled by varying the St feeding amount.The result of effects of the polymerization process on the particle size and size distribution of nanoparticles shows that the modified microemulsion polymerization process(semi-continuous and pre-emulsification) possesses great superiority in preparing narrowly distributed polymer nanoparticles.