阳离子和两性表面活性剂在聚甲基丙烯酸甲酯表面的吸附行为

利用座滴法研究了阳离子表面活性剂十六烷基醚羟丙基季铵盐(C₁₆PC)、十六烷基聚氧乙烯醚羟丙基季铵盐(C₁₆(EO)₃PC)和两性离子表面活性剂十六烷基醚羟丙基羧酸甜菜碱(C₁₆PB)、十六烷基聚氧乙烯醚羟丙基羧酸甜菜碱(C₁₆(EO)₃PB)溶液在聚甲基丙烯酸甲酯(PMMA)表面上的润湿性质, 考察了表面活性剂类型及浓度对接触角的影响趋势. 研究发现: 低浓度条件下表面活性剂分子可能以平躺的方式吸附到固体界面, 且亲水基团靠近固体界面, PMMA表面被轻微疏水化; 在高浓度时则通过Lifshitz-van der Waals 作用吸附, 亲水基团在外, PMMA表面被亲水改性. 聚氧乙烯基团(EO基团)的引入对阳离子表面活性剂的接触角影响不大; 而含有聚氧乙烯基团的两性离子表面活性剂在PMMA界面上以类似半胶束的聚集体吸附, 大幅度降低接触角.

Adsorption Behavior of Cationic and Zwitterionic Surfactants on Poly(methyl methacrylate)

The wetting behavior of poly(methyl methacrylate) (PMMA) surfaces by aqueous solutions of cationic surfactants, hexadecanol glycidyl ether ammonium chloride (C₁₆PC), hexadecanol polyoxyethylene (3) glycidyl ether ammonium chloride (C₁₆(EO)₃PC), and zwitterionic surfactants, hexadecanol glycidyl ether glycine betaine (C₁₆PB) and hexadecanol polyoxyethylene(3) glycidyl ether glycine betaine (C₁₆(EO)₃PB), were investigated by sessile drop analysis. The influence of surfactant type and concentration on contact angle was determined. The PMMA surface is modified hydrophobically only slightly at low bulk concentration because the surfactant molecules are parallel to the substrate surface and the hydrophilic groups are close to the surface. However, at high concentration, the surfactant molecules can adsorb onto the PMMA surface through Lifshitz-van der Waals interactions and hydrophilic groups directed towards the bulk phase of solution, which increases the hydrophilic character of the PMMA surface. The contact angles of cationic surfactants show little variation following the insertion of polyoxyethylene units. However, the presence of polyoxyethylene units in the zwitterionic surfactants leads to an obvious decrease of contact angle because of the formation of hemimicelles on the PMMA surface.