Riley John K, Matyjaszewski Krzysztof, Tilton Robert D
Center for Complex Fluids Engineering, †Department of Chemical Engineering, ‡Department of Chemistry, and §Department of Biomedical Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
Langmuir. 2014 Apr 15;30(14):4056-65. doi: 10.1021/la500570u. Epub 2014 Apr 2.
Adsorption of 20 nm diameter silica nanoparticles grafted with a high density brush of the weak polymeric base poly(2-(dimethylamino)ethyl methacrylate) (SiO2-g-PDMAEMA) to the silica/aqueous interface was investigated using ellipsometry and streaming potential measurements. We measured SiO2-g-PDMAEMA adsorption to negatively charged silica surfaces in 1-100 mM sodium chloride solutions in the pH range 5-10 to investigate the role of electrostatics in the adsorption mechanism. In this system pH and ionic strength determine not only the charge density of the silica adsorption substrate but also the degree of ionization and swelling of the PDMAEMA brushes on the nanoparticles, resulting in nonmonotonic dependences of the extent of adsorption on pH and ionic strength. SiO2-g-PDMAEMA displays significantly different adsorption behavior from the linear PDMAEMA analogue, most notably in terms of a strongly hysteretic adsorption response to altered pH and a greater tendency to adsorb under weak surface attraction conditions that prevail at high pH.
使用椭偏仪和流动电势测量法研究了接枝有弱聚合物碱聚（甲基丙烯酸 2-（二甲氨基）乙酯）（SiO2-g-PDMAEMA）高密度刷的 20 纳米直径二氧化硅纳米颗粒在二氧化硅/水界面的吸附情况。我们在 pH 范围为 5 - 10 的 1 - 100 mM 氯化钠溶液中测量了 SiO2-g-PDMAEMA 在带负电的二氧化硅表面的吸附，以研究静电作用在吸附机制中的作用。在该体系中，pH 和离子强度不仅决定了二氧化硅吸附底物的电荷密度，还决定了纳米颗粒上 PDMAEMA 刷的电离程度和溶胀程度，导致吸附程度对 pH 和离子强度呈现非单调依赖性。SiO2-g-PDMAEMA 表现出与线性 PDMAEMA 类似物显著不同的吸附行为，最明显的是对 pH 变化有强烈的滞后吸附响应，以及在高 pH 时占主导的弱表面吸引力条件下有更大的吸附倾向。
