Nakano Takanori, Saito Naohiko, Minami Hideto
Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Rokko, Nada, Kobe 657-8501, Japan.
General Center of R&D, Toagosei Co., Ltd., 8 Showacho, Minato-ku, Nagoya, Aichi 455-0026, Japan.
Langmuir. 2020 Oct 13;36(40):11957-11962. doi: 10.1021/acs.langmuir.0c02060. Epub 2020 Sep 29.
Water-soluble polymers such as poly(acrylic acid) (PAA) are widely applied in dispersants, thickeners, flocculants, and superabsorbent polymers. Here, submicrometer-sized monodisperse PAA particles were successfully prepared by precipitation polymerization in acetonitrile at 55 °C with 2,2'-azobis(2,4-dimethylvaleronitrile) as an initiator. In a medium with a high dielectric constant, the particles were stabilized by electrostatic repulsion without a colloidal stabilizer during the polymerization. Moreover, the obtained PAA particles were spontaneously cross-linked in the absence of a cross-linker. The degree of the cross-linking was strongly dependent on the amount of water (500-10,000 ppm) in the polymerization medium. The PAA particles swelled more with acrylic acid with an increase in the amount of water. Thus, in the case of high water content, the particles would become the main polymerization loci, which in turn results in the cross-linking structures owing to the α-hydrogen abstraction of PAA chains during the polymerization.
水溶性聚合物，如聚丙烯酸（PAA），广泛应用于分散剂、增稠剂、絮凝剂和高吸水性聚合物中。在此，以2,2'-偶氮二（2,4-二甲基戊腈）为引发剂，通过在55℃的乙腈中进行沉淀聚合，成功制备了亚微米级单分散PAA颗粒。在高介电常数的介质中，聚合过程中颗粒通过静电排斥作用得以稳定，无需胶体稳定剂。此外，所制备的PAA颗粒在没有交联剂的情况下会自发交联。交联程度强烈依赖于聚合介质中的水量（500 - 10,000 ppm）。随着水量增加，PAA颗粒与丙烯酸的溶胀程度更大。因此，在高含水量的情况下，颗粒会成为主要的聚合位点，这进而由于聚合过程中PAA链的α-氢提取而导致交联结构的形成。
