In emulsifier-free, emulsion polymerization with ionizable comonomer, the ionization of the comonomer is critical in determining the size of the final polymeric particles at sub-micrometer scale. In this study, polystyrene latex beads with carboxylates on the surface were synthesized using acrylic acid as a comonomer. Specifically, ammonium hydroxide was added to the emulsifier-free polymerization system to promote the ionization of acrylic acid by increasing pH. Smaller polystyrene latex particles were produced by increasing the ammonium hydroxide concentration in the reaction system, due to the enhanced stability promoted by the ionization of acrylic acid during the nucleation step. In addition, the surface morphology of the polystyrene latex particles was controlled by the concentration of acrylic acid, the dissociation of which was influenced by the ammonium hydroxide concentration.

中文翻译：

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无乳化剂聚合反应中通过氢氧化铵控制羧基化聚苯乙烯胶乳颗粒的尺寸和表面形态

在无乳化剂，可电离的共聚单体的乳液聚合中，共聚单体的电离对于确定最终聚合物颗粒的亚微米级尺寸至关重要。在这项研究中，使用丙烯酸作为共聚单体合成了表面具有羧酸盐的聚苯乙烯胶乳珠。具体地，将氢氧化铵加入到无乳化剂的聚合体系中，以通过增加pH来促进丙烯酸的电离。通过增加反应体系中氢氧化铵的浓度，可以生产出较小的聚苯乙烯胶乳颗粒，这是由于成核步骤中丙烯酸的电离促进了稳定性的提高。另外，聚苯乙烯胶乳颗粒的表面形貌由丙烯酸的浓度控制，