Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway.
J Phys Chem B. 2012 Sep 13;116(36):11386-95. doi: 10.1021/jp306833x. Epub 2012 Aug 29.
Effects of temperature on the association behavior in aqueous solutions of a series of charged thermoresponsive poly(N-isopropylacrylamide)-block-poly((3-acrylamidopropyl) trimethylammonium chloride) (abbreviated as PNIPAAM(n)-b-PAMPTMA(+)(20)) with different lengths of the PNIPAAM block (n = 24, 48, and 65) have been studied with the aid of turbidimetry, zeta sizer, and dynamic light scattering (DLS). The turbidity results show that the transition to high turbidity values is shifted to lower temperatures when the length of the PNIPAAM block increases. It was observed that the value of the cloud point (CP) dropped with increasing polymer concentration, enlarged length of the PNIPAAM block, and augmented salinity. It was found that the decay of the correlation function from DLS is bimodal at temperatures well below CP, where the fast mode represents the motion of the unimers and the slow mode the dynamics of micelles/intermicellar complexes. At higher temperatures, larger particles of the system grow at the expense of the smaller ones in the spirit of Ostwald ripening, and clusters with a narrow size distribution evolve at high temperatures. By adding salt (NaCl), enhanced aggregation occurs at elevated temperatures because of screening of Coulomb repulsions.
温度对一系列带电荷的温敏性聚（N-异丙基丙烯酰胺）-嵌段-聚（（3-丙烯酰胺丙基）三甲基氯化铵）（缩写为 PNIPAAM(n)-b-PAMPTMA(+)(20)）在水溶液中的缔合行为的影响，其中 PNIPAAM 嵌段的长度不同（n = 24、48 和 65），已经通过浊度法、ζ 粒径仪和动态光散射（DLS）进行了研究。浊度结果表明，当 PNIPAAM 嵌段的长度增加时，向高浊度值转变的温度向低温移动。观察到浊点（CP）的值随着聚合物浓度的增加、PNIPAAM 嵌段的长度增大以及盐度的增加而降低。发现 DLS 中相关函数的衰减在低于 CP 的温度下呈双峰模式，其中快模式代表单体的运动，慢模式代表胶束/胶束复合物的动力学。在较高的温度下，系统中的较大颗粒会在奥斯特瓦尔德成熟的作用下消耗较小颗粒而生长，并且在高温下会出现具有较窄粒径分布的聚集体。通过添加盐（NaCl），由于库仑斥力的屏蔽作用，在较高的温度下会发生增强的聚集。
