Advanced synthesis for monodisperse polymer nanoparticles in aqueous media with sub-millimolar surfactants
Advanced synthesis for monodisperse polymer nanoparticles in aqueous media with sub-millimolar surfactants
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DOI：
10.1016/j.polymer.2014.04.011
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发表时间：
2014-06
期刊：
影响因子：
4.6
通讯作者：
H. Ishii;M. Ishii;D. Nagao;M. Konno
中科院分区：
文献类型：
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作者：
H. Ishii;M. Ishii;D. Nagao;M. Konno
以两性引发剂(VA-057)为引发剂，在亚毫摩尔浓度的阴离子表面活性剂存在下，通过水乳液聚合合成了平均粒径小于100 nm的高度单分散聚苯乙烯纳米粒子。由于在中性pH下引发剂上的净电荷几乎为零，所得胶乳颗粒的大小主要由表面活性剂的吸附决定。通过改变表面活性剂、引发剂和单体的浓度以及离子强度，在一系列具有不同临界胶束浓度(CMC)的阴离子表面活性剂存在下进行聚合。十二烷基苯磺酸钠(SDBS)、十六烷基硫酸钠(SHS)和十八烷基硫酸钠(SOS)的CMC相对较低，因此能够在相对较低的(亚毫米级)表面活性剂浓度下形成高度单分散的纳米颗粒，CS(即在每种情况下都低于CMC)。实验发现，颗粒数Np和颗粒大小变异系数Cv强烈依赖于Ccs/CMC比值：Np几乎与这一比值的平方成正比增加，而Cv在CS/CMC=0.20时表现出最小值。较高的离子强度减小了表面活性剂的粒径，这与上述关系是一致的，因为盐的加入降低了离子表面活性剂的cmcs。使用这种配方生产的聚合物乳胶颗粒形成高度规则、紧密堆积的胶体阵列。
Highly monodisperse polystyrene nanoparticles with mean diameters of less than 100 nm are synthesized via aqueous emulsion polymerization using an amphoteric initiator (VA-057) in the presence of sub-millimolar concentrations of anionic surfactant. Since the net charge on the initiator is almost zero at neutral pH, the resultant latex particle size is mainly determined by surfactant adsorption. Polymerizations were performed in the presence of a range of anionic surfactants with differing critical micelle concentrations (CMC) by varying the concentrations of surfactant, initiator and monomer, and also the ionic strength. Sodium dodecyl benzene sulfonate (SDBS), sodium hexadecyl sulfate (SHS), and sodium octadecyl sulfate (SOS) have relatively low CMCs and so enable formation of highly monodisperse nanoparticles at relatively low (sub-millimolar) surfactant concentrations,CS(i.e. below the CMC in each case). Empirically, it was found that the particle number,Np, and coefficient of variation of the particle size,CV, were strongly dependent on theCS/CMC ratio:Npincreased almost in proportion with the square of this ratio, while theCVexhibited a minimum at approximatelyCS/CMC = 0.20. Higher ionic strength reduced the particle size, which is consistent with the above relationship because the addition of salt lowers the CMCs of ionic surfactants. Polymer latex particles produced using such formulations form highly regular, close-packed colloidal arrays.