超声均质微悬浮聚合制备亚微米级聚苯乙烯胶粒

以苯乙烯St为代表性单体，以聚乙烯醇PVA为分散剂，以十六烷HD为助稳定剂，以亚硝酸钠NaNO₂为水相阻聚剂，通过基于超声均质化的微悬浮聚合制得了一系列亚微米级聚苯乙烯胶粒。对亚微米级单体液滴的均质化产生及后续聚合过程中分散相尺寸的变化进行了考察。发现超声均质化和高分子分散剂的结合有利于制备粒径小、分布窄的稳定微悬浮液滴，而吸附于液滴表面的高分子分散剂、油相内的助稳定剂及水相中的阻聚剂的协同作用能使聚合过程较好地保持分散相原有的粒径大小及分布。因而通过改变超声均质强度，可较容易地在0.5～3.5 μm范围内自由调节胶粒的平均粒径。相对于常规的剪切均质微悬浮聚合，超声均质微悬浮聚合可更好地填补（细）乳液聚合与悬浮聚合在粒径分布范围上的间隙，有望高效、高容量地微胶囊化包裹亚微米级目标内容物。

Preparation of submicron polystyrene particles by micro-suspension polymerization with ultrasonic homogenization

Using styrene as typical monomer, polyvinyl alcohol PVA as dispersant, hexadecane HD as co-stabilizer, NaNO₂ as water-soluble polymerization inhibitor, a series of submicron polystyrene particles were prepared by micro-suspension polymerization with the help of ultrasonic homogenization. The formation of submicron droplets during homogenization and the variation of particles size and size distribution of disperse phase during polymerization were investigated. It was found that the combination of ultrasonic homogenization and polymer dispersant was conducive to reducing the size of monomer droplet and stabilizing the micro-suspension. The synergistic effect of PVA adsorbed on the surface of droplets, HD dispersed in the droplets phase and NaNO₂ dispersed in the water phase facilitated maintenance of disperse phase size during polymerization. Thus the size of colloidal particles could be controlled by varying ultrasonic intensity. Comparing with the conventional micro-suspension polymerization using shear homogenization, the micro-suspension polymerization using ultrasonic homogenization was more suitable to fill the particle size gap between (mini-)emulsion polymerization and suspension polymerization, and more likely to encapsulate the submicron target contents.