Fajalia Ankitkumar I, Tsianou Marina
Department of Chemical & Biological Engineering, University at Buffalo, The State University of New York (SUNY) , Buffalo, New York 14260-4200, United States.
J Phys Chem B. 2014 Sep 11;118(36):10725-39. doi: 10.1021/jp5023168. Epub 2014 Sep 2.
Aqueous formulations containing polymers and surfactants find several applications in pharmaceutics, coatings, inks, and home products. The association between polymers and surfactants contributes greatly to the function of these complex fluids, however, the effects of polar organic solvents, ubiquitous in formulations, remain mostly unexplored. We have analyzed small angle neutron scattering (SANS) data to determine the conformation of a "model" nonionic polymer, poly(ethylene oxide) (PEO), in aqueous solutions as affected by the presence of an ionic surfactant, sodium dodecyl sulfate (SDS), and subsequent addition of short-chain alcohol (ethanol or 2-propanol). PEO chains (MW = 90,000) are Gaussian in dilute aqueous solutions, but become polyelectrolyte-like upon the addition of 30 mM SDS, with about 6 SDS micelles bound to each PEO chain. Micelles associated with polymer are similar in structure and interactions to micelles that form in aqueous solutions in the absence of polymer. Addition of alcohol alters both the polymer and micelle structure and interactions, leads to detachment of micelles from the polymer, and the PEO chains regain their Gaussian conformation. 2-Propanol is more effective than ethanol in influencing the polymer conformation and the properties of SDS micelles in aqueous solutions, either in the presence or in the absence of PEO. This study contributes fundamental insights on polymer and surfactant organization in solution, as well as new, quantitative information on systems that are widely used in practice.
含有聚合物和表面活性剂的水性制剂在制药、涂料、油墨和家用产品中有多种应用。聚合物和表面活性剂之间的缔合对这些复杂流体的功能有很大贡献，然而，制剂中普遍存在的极性有机溶剂的影响大多仍未得到探索。我们分析了小角中子散射（SANS）数据，以确定“模型”非离子聚合物聚环氧乙烷（PEO）在水溶液中的构象，该构象受离子表面活性剂十二烷基硫酸钠（SDS）的存在以及随后添加短链醇（乙醇或2-丙醇）的影响。PEO链（分子量=90,000）在稀水溶液中呈高斯分布，但在加入30 mM SDS后变成类似聚电解质的结构，每条PEO链约结合6个SDS胶束。与聚合物缔合的胶束在结构和相互作用上与在无聚合物的水溶液中形成 的胶束相似。添加醇会改变聚合物和胶束的结构及相互作用，导致胶束从聚合物上脱离，PEO链恢复其高斯构象。在有或没有PEO的情况下，2-丙醇在影响聚合物构象和水溶液中SDS胶束性质方面比乙醇更有效。这项研究为溶液中聚合物和表面活性剂的组织提供了基本见解，以及关于实际中广泛使用的体系的新的定量信息。
