Penfold J, Staples E, Tucker I, Thompson L, Thomas R K
ISIS Facility, CLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK.
J Colloid Interface Sci. 2002 Mar 15;247(2):404-11. doi: 10.1006/jcis.2001.8042.
Specular neutron reflection has been used to investigate the effects of temperature and added electrolyte on the adsorption of nonionic surfactants and nonionic surfactant mixtures at the air-water interface. For the alkyl poly-oxyethylene oxide nonionic surfactants, C(n)EO(m), the adsorption at the air-water interface is independent of temperature for surfactants with shorter ethylene oxide groups, whereas there is an increasing tendency for increased adsorption with temperature for surfactants with longer ethylene oxide groups. The addition of "salting in" (sodium thiocyanate, NaSCN) and "salting out" (sodium chloride, NaCl, sodium sulphate, Na2SO4) electrolyte results in reduced and enhanced adsorption, respectively, for C12EO8, whereas both types of electrolyte result in enhanced adsorption for C12EO12. The addition of electrolyte does not substantially alter the temperature dependence of the adsorption of the pure monolayers. For the nonionic mixtures of C12EO3/C12EO8 increasing temperature results in a surface richer in the least surface-active component, C12EO8. For the same nonionic mixture, the addition of "salting in" and "salting out" electrolyte results in an reduced and increased adsorption, respectively. The addition of "salting in" electrolyte results in a surface more rich in C12EO3, whereas for the addition of both "salting in" and "salting out" electrolyte the surface composition is essentially unaltered.
镜面中子反射已被用于研究温度和添加电解质对非离子表面活性剂及非离子表面活性剂混合物在气-水界面吸附的影响。对于烷基聚环氧乙烷非离子表面活性剂C(n)EO(m)，环氧乙烷链较短的表面活性剂在气-水界面的吸附与温度无关，而环氧乙烷链较长的表面活性剂的吸附则有随温度升高而增加的趋势。添加“盐溶”（硫氰酸钠，NaSCN）和“盐析”（氯化钠，NaCl，硫酸钠，Na2SO4）电解质，对于C12EO8分别导致吸附减少和增加，而对于C12EO12两种类型的电解质均导致吸附增加。添加电解质基本不会改变纯单分子层吸附的温度依赖性。对于C12EO3/C12EO8的非离子混合物，温度升高会导致表面富含表面活性最低的组分C12EO8。对于相同的非离子混合物，添加“盐溶”和“盐析”电解质分别导致吸附减少和增加。添加“盐溶”电解质会使表面更富含C12EO3，而同时添加“盐溶”和“盐析”电解质时，表面组成基本不变。
