Physical Chemistry, Kemicentrum, Lund University, Box 124, SE-221 00, Lund, Sweden.
ACS Appl Mater Interfaces. 2011 Jul;3(7):2451-62. doi: 10.1021/am200350z. Epub 2011 Jun 27.
The adsorption from mixed polyelectrolyte-surfactant solutions at hydrophobized silica surfaces was investigated by in situ null-ellipsometry, and compared to similar measurements for hydrophilic silica surfaces. Three synthetic cationic copolymers of varying hydrophobicity and one cationic hydroxyethyl cellulose were compared in mixtures with the anionic surfactant sodium dodecylsulfate (SDS) in the absence or presence of a dilute silicone oil emulsion. The adsorption behavior was mapped while stepwise increasing the concentration of SDS to a polyelectrolyte solution of constant concentration. The effect on the deposition of dilution of the bulk solution in contact with the surface was also investigated by gradual replacement of the bulk solution with 1 mM aqueous NaCl. An adsorbed layer remained after complete exchange of the polyelectrolyte/surfactant solution for aqueous NaCl. In most cases, there was a codeposition of silicone oil droplets, if such droplets were present in the formulation before dilution. The overall features of the deposition were similar at hydrophobic and hydrophilic surfaces, but there were also notable differences. SDS molecules adsorbed selectively at the hydrophobized silica surface, but not at the hydrophilic silica, which influenced the coadsorption of the cationic polymers. The largest amount of deposited material after dilution was found for hydrophilic silica and for the least-hydrophobic cationic polymers. For the least-hydrophobic polyions, no significant codeposition of silicone oil was detected at hydrophobized silica after dilution if the initial SDS concentration was high.
通过原位椭圆偏光法研究了疏水化二氧化硅表面上混合聚电解质-表面活性剂溶液的吸附，并与亲水二氧化硅表面的类似测量进行了比较。在不存在或存在稀硅油乳液的情况下，将三种不同疏水性的合成阳离子共聚物和一种阳离子羟乙基纤维素与阴离子表面活性剂十二烷基硫酸钠（SDS）进行了比较。在逐步增加 SDS 浓度至恒定浓度的聚电解质溶液的过程中，绘制了吸附行为图。还通过逐渐用 1 mM 水溶液 NaCl 替代与表面接触的大量溶液，研究了稀释对大量溶液沉积的影响。在完全用 NaCl 水溶液替换聚电解质/表面活性剂溶液后，仍会留下吸附层。在疏水和亲水表面上，沉积的总体特征相似，但也存在明显的差异。SDS 分子在疏水化二氧化硅表面上选择性吸附，但不在亲水二氧化硅表面上吸附，这影响了阳离子聚合物的共吸附。在稀释后，沉积的材料量最大的是亲水二氧化硅和疏水性最小的阳离子聚合物。对于疏水性最小的聚离子，如果初始 SDS 浓度较高，则在稀释后疏水化二氧化硅上不会检测到硅油的明显共沉积。
