Laboratory of Interfaces and Nanosize Systems, Institute for Chemistry, Eötvös Loránd University, Post Office Box 32, H-1117 Budapest, Hungary.
Langmuir. 2011 Apr 5;27(7):3461-7. doi: 10.1021/la200312g. Epub 2011 Mar 11.
The interaction of cetyl-trimethylammonium bromide (CTAB) with swollen and collapsed poly(N-isopropylacrylamide) (pNIPAM) monodisperse nanogel particles was investigated by electrophoretic mobility, dynamic light scattering, and potentiometric surfactant activity measurements. The surfactant binds to the nanogel particles as monomers in the whole CTAB concentration range and binds in the form of surfactant aggregates as well above a critical concentration (cac) in both the swollen and collapsed state of the pNIPAM. The swollen particle system is a thermodynamically stable solution. The collapsed nanogel particle system is an electrically stabilized colloid dispersion, which coagulates when the particles are near the electrically neutral state. An analytically undetectably small amount of surfactant binding (5 × 10(-7) mol/g of pNIPAM) leads to a dramatic effect on the stability of the pNIPAM nanogel system. The electrokinetic potential versus surfactant concentration functions unexpectedly strongly depend upon the temperature around the lower critical solution temperature (LCST) of the polymer, which was interpreted by the change of the polymer segment density in the surface layer of the collapsing nanogel particles.
十六烷基三甲基溴化铵（CTAB）与溶胀和塌陷的聚（N-异丙基丙烯酰胺）（pNIPAM）单分散纳米凝胶颗粒的相互作用通过电泳迁移率、动态光散射和等电位表面活性剂活性测量进行了研究。在整个 CTAB 浓度范围内，表面活性剂以单体形式结合到纳米凝胶颗粒上，并且在溶胀和塌陷状态下的 pNIPAM 中，在临界浓度（cac）以上也以表面活性剂聚集体的形式结合。溶胀颗粒体系是热力学稳定的溶液。塌陷纳米凝胶颗粒体系是电稳定的胶体分散体，当颗粒接近电中性状态时会凝聚。表面活性剂结合量（pNIPAM 的 5×10(-7) mol/g）非常小，但对 pNIPAM 纳米凝胶体系的稳定性有显著影响。电动电势与表面活性剂浓度函数出乎意料地强烈依赖于聚合物下临界溶液温度（LCST）周围的温度，这可以通过塌陷纳米凝胶颗粒表面层中聚合物链段密度的变化来解释。
