Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, China.
J Phys Chem B. 2010 Mar 25;114(11):3799-803. doi: 10.1021/jp9121694.
In the present study, we have prepared poly(N-isopropylacrylamide-co-vinylbenzyl trimethylammonium chloride) (NIPAM-co-VT) and poly(N-isopropylacrylamide-co-sodium acrylate) (NIPAM-co-SA) thermally sensitive microgels, which are positively and negatively charged, respectively. By use of laser light scattering (LLS), we have investigated the temperature-induced aggregation of microgels in the presence of salts with the same cation but different anions. The studies demonstrate that neither kosmotropic nor chaotropic anions can lead to the aggregation of NIPAM-co-VT microgels. No obvious specific anion effects can be observed in the phase transition of NIPAM-co-VT microgels. However, kosmotropic and chaotropic anions lead to the aggregation of NIPAM-co-SA microgels. The ordering of anions based on the aggregation temperature at the same salt concentration is consistent with the typical Hofmeister series. The aggregation is thought to be determined by the indirect interfacial effects of anions near the microgel surface. Additionally, the aggregate size of microgels increases with salt concentration for the kosmotropic anions.
在本研究中，我们制备了带正电和负电的聚（N-异丙基丙烯酰胺-co-乙烯基苄基三甲基氯化铵）（NIPAM-co-VT）和聚（N-异丙基丙烯酰胺-co-丙烯酸钠）（NIPAM-co-SA）热敏性微凝胶。我们使用激光光散射（LLS）研究了在具有相同阳离子但不同阴离子的盐存在下微凝胶的温度诱导聚集。研究表明，无论是亲核性还是疏核性阴离子都不能导致 NIPAM-co-VT 微凝胶的聚集。在 NIPAM-co-VT 微凝胶的相变中，没有观察到明显的特定阴离子效应。然而，亲核性和疏核性阴离子会导致 NIPAM-co-SA 微凝胶的聚集。根据相同盐浓度下的聚集温度对阴离子进行排序，与典型的 Hofmeister 序列一致。这种聚集被认为是由阴离子在微凝胶表面附近的间接界面效应决定的。此外，对于亲核性阴离子，微凝胶的聚集尺寸随盐浓度的增加而增加。
