Yamamoto Tetsuya, Nakayama Masaki, Kanda Yoichi, Higashitani Ko
Department of Chemical Engineering, Kyoto University-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
J Colloid Interface Sci. 2006 May 1;297(1):112-21. doi: 10.1016/j.jcis.2005.10.025. Epub 2005 Nov 16.
To clarify the growth mechanism of polystyrene (PSL) particles in the soap-free polymerization, characteristics of not only particles but also polymeric materials floating in the bulk were investigated on the molecular scale by using atomic force microscope (AFM), where a cationic initiator V-50 is used to make the formed polymeric materials transfer on the mica plate in sampling. Our main attention here is to know the reason why the particle size increases with increasing initiator concentration in the production of PSL particles. The following are found. (1) As far as the initiators and monomers remain in the bulk solution, the polymeric materials are born in the bulk continuously, because of the slow decomposition rate of initiators. (2) The growth of particles at the early stage of t(r) > or = 0.75 h is considered to be attributable mainly to the particle swelling by absorbing monomers from the bulk. The rapid growth at the intermediate stage is due to the deposition of polymeric materials in the bulk on the particle surface and their simultaneous swelling by monomers in the bulk. (3) The reason why the particle size increases with increasing concentration of initiator is that the growth process is controlled by the deposition rate of polymeric materials in the bulk whose amount increases with the initiator concentration. (4) The particle size and the smoothness of particle surface depend on the relative concentration of initiators and monomers remained.
为阐明无皂聚合中聚苯乙烯（PSL）颗粒的生长机制，通过原子力显微镜（AFM）在分子尺度上研究了颗粒以及本体中漂浮的聚合物材料的特性，其中使用阳离子引发剂V - 50使形成的聚合物材料在取样时转移到云母片上。我们在此主要关注的是了解在PSL颗粒生产中粒径为何随引发剂浓度增加而增大。发现如下：（1）只要引发剂和单体保留在本体溶液中，由于引发剂分解速率缓慢，聚合物材料就会在本体中持续生成。（2）在t(r)≥0.75 h的早期阶段颗粒的生长主要被认为是由于颗粒从本体中吸收单体而发生溶胀。中间阶段的快速生长是由于本体中的聚合物材料沉积在颗粒表面以及它们同时被本体中的单体溶胀。（3）粒径随引发剂浓度增加而增大的原因是生长过程由本体中聚合物材料的沉积速率控制，而聚合物材料的量随引发剂浓度增加。（4）粒径和颗粒表面的光滑度取决于剩余引发剂和单体的相对浓度。
