Effect of polymer molecular weight and solution pH on the surface properties of sodium dodecylsulfate-poly(ethyleneimine) mixtures.
Effect of polymer molecular weight and solution pH on the surface properties of sodium dodecylsulfate-poly(ethyleneimine) mixtures.
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DOI：
10.1021/la302444b
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
S. Halacheva;J. Penfold;R. Thomas;J. Webster
中科院分区：
文献类型：
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作者：
S. Halacheva;J. Penfold;R. Thomas;J. Webster
通过空气-溶液界面的表面张力 ST 和中子反射率 NR，研究了聚合物分子量和溶液 pH 对阴离子表面活性剂十二烷基硫酸钠、SDS 和一系列不同分子量的小型线性聚（乙烯亚胺）、PEI、聚电解质的表面性质的影响。强烈的 SDS-PEI 相互作用产生了复杂的 ST 行为模式，该模式很大程度上取决于溶液 pH 值和 PEI 分子量。 ST 数据与使用 NR 获得的表面吸附和表面结构的更直接测定广泛相关。在 pH 3、7 和 10 时，强烈的 SDS-PEI 相互作用导致在相对较低的 SDS 和 PEI 浓度下明显的 SDS 吸附，并且在很大程度上与 pH 和 PEI 分子量无关（对于 PEI 分子量约为 320、640 和 2000 Da）。在 pH 7 和 10 下，SDS 和 PEI 浓度的组合可形成表面多层结构。对于分子量为 320 和 640 Da 的 PEI，这些表面多层结构在 pH 10 时最为发达，而在 pH 7 时则较差。在分子量为 2000 Da 时，它们在 pH 7 和 10 下均较差。表面结构随分子量的变化与之前的研究一致，(1) 对于分子量为 25,000 Da 的线性 PEI，没有观察到多层结构。结果表明，由于聚合物在控制表面多层形成方面的灵活性，熵贡献随着聚合物分子量的增加而变得重要。
The effect of polymer molecular weight and solution pH on the surface properties of the anionic surfactant sodium dodecylsulfate, SDS, and a range of small linear poly(ethyleneimine), PEI, polyelectrolytes of different molecular weights has been studied by surface tension, ST, and neutron reflectivity, NR, at the air-solution interface. The strong SDS-PEI interaction gives rise to a complex pattern of ST behavior which depends significantly on solution pH and PEI molecular weight. The ST data correlate broadly with the more direct determination of the surface adsorption and surface structure obtained using NR. At pH 3, 7, and 10, the strong SDS-PEI interaction results in a pronounced SDS adsorption at relatively low SDS and PEI concentrations, and is largely independent of pH and PEI molecular weight (for PEI molecular weights on the order of 320, 640, and 2000 Da). At pH 7 and 10, there are combinations of SDS and PEI concentrations for which surface multilayer structures form. For the PEI molecular weights of 320 and 640 Da, these surface multilayer structures are most well-developed at pH 10 and less so at pH 7. At the molecular weight of 2000 Da, they are poorly developed at both pH 7 and 10. This evolution in the surface structure with molecular weight is consistent with previous studies, (1) where for a molecular weight of 25,000 Da no multilayer structures were observed for the linear PEI. The results show the importance with increasing polymer molecular weight of the entropic contribution due to the polymer flexibility in control of the surface multilayer formation.