Medway Sciences, School of Science, University of Greenwich at Medway, Chatham Maritime, Kent ME4 4TB, UK.
Adv Colloid Interface Sci. 2010 Jul 12;158(1-2):15-20. doi: 10.1016/j.cis.2009.07.008. Epub 2009 Aug 5.
A series of cationic poly(N-isopropylacrylamide/4-vinylpyridine) [poly(NIPAM/4-VP)] polyelectrolyte co-polymer microgels have been prepared by surfactant free emulsion polymerization (SFEP) with varying compositions of 4-VP and NIPAM. The compositions of 4-VP were 15, 25, 35, 45, 55wt.% relative to NIPAM. The temperature and pH responsive swelling-deswelling properties of these microgels have been investigated using dynamic light scattering (DLS) and electrophoretic mobility measurements. DLS results have shown that the particle diameter of the poly(NIPAM/4-VP) microgels decreases with increasing concentration (wt.%) of 4-VP over the 20-60 degrees C temperature range due to the increased amount of hydrophobic group. The particle size of all poly(NIPAM/4-VP) microgel series increases with decreasing pH, as the 4-VP units become more protonated at low pH below the pK(a) (5.39) of the monomer 4-VP. Electrophoretic mobility results have shown that electrophoretic mobility increases as the temperature/pH increases at a constant background ionic strength (1x10(-4)mol dm(-3) NaCl). These results are in good agreement with DLS results. The temperature/pH sensitivity of these microgels depends on the ratio of NIPAM/4-VP concentration in the co-polymer microgel systems. The combined temperature/pH responsiveness of these polyelectrolyte microgels can be used in applications where changes in particle size with small change in pH or temperature is of great consequence.
已通过无表面活性剂乳液聚合（SFEP）制备了一系列阳离子聚（N-异丙基丙烯酰胺/4-乙烯基吡啶）[聚（NIPAM/4-VP）]共聚高分子微凝胶，其 4-VP 和 NIPAM 的组成比变化。4-VP 的组成分别为相对于 NIPAM 的 15、25、35、45、55wt％。使用动态光散射（DLS）和电泳迁移率测量研究了这些微凝胶的温敏和 pH 响应溶胀-收缩性质。DLS 结果表明，随着 4-VP 浓度（wt.％）在 20-60°C 温度范围内的增加，聚（NIPAM/4-VP）微凝胶的粒径减小，这是由于疏水性基团的增加。所有聚（NIPAM/4-VP）微凝胶系列的粒径均随 pH 值的降低而增大，因为在低于单体 4-VP 的 pK（a）（5.39）的低 pH 下，4-VP 单元质子化更多。电泳迁移率结果表明，在恒定背景离子强度（1x10（-4）mol dm（-3）NaCl）下，随着温度/ pH 的升高，电泳迁移率增加。这些结果与 DLS 结果吻合良好。这些微凝胶的温度/pH 敏感性取决于共聚微凝胶体系中 NIPAM/4-VP 浓度的比值。这些聚电解质微凝胶的组合温度/pH 响应性可用于颗粒尺寸随 pH 或温度的微小变化而发生重大变化的应用中。
