Centre for Surface Science, Physical Chemistry Section, Department of Chemistry, Jadavpur University, Kolkata 700032, India.
Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, JD-Block, Sec-III, Salt Lake, Kolkata700106, India.
Langmuir. 2021 May 25;37(20):6168-6177. doi: 10.1021/acs.langmuir.1c00273. Epub 2021 May 8.
Polymer/surfactant composites have emerged as a subject of interest for their diverse applications. The improved solution properties in polymer/surfactant composites have been correlated to the formation of premicellar surfactant aggregate-polymer complexes (PS) at a surfactant concentration well below their critical micelle concentrations. Using different physicochemical and spectroscopic techniques here we have studied PS formed by hydroxypropyl cellulose, a nonionic-biocompatible polymer, and alkyl sulfate surfactants of different tail lengths. Our study shows that an increase in surfactant tail length eases PS formation and enhances PS-induced polymer cross-linking and, correspondingly, solution viscosity. PS consisting of shorter tail surfactants and those with longer tail surfactants differ microscopically as the former offers more polar interior than the later as evidenced from fluorescence measurements. Our study establishes that shorter tail surfactants intend to stay loosely packed inside PS and allow larger water penetration, which creates a relatively polar hydrophobic core compared to the PS with longer tail surfactants. The stronger packing of PS with longer tail surfactants is an outcome of favorable interaction between polymer polar groups and surfactant headgroups, which further creates strongly hydrogen-bonded water in their hydration shell.
聚合物/表面活性剂复合材料因其多样化的应用而成为研究热点。在表面活性剂浓度远低于其临界胶束浓度的情况下，形成预胶束表面活性剂聚集体-聚合物复合物（PS），改善了聚合物/表面活性剂复合材料的溶液性能。本文采用不同的物理化学和光谱技术，研究了羟丙基纤维素（一种非离子型生物相容聚合物）和不同链长的烷基硫酸盐表面活性剂形成的 PS。研究表明，表面活性剂链长的增加有利于 PS 的形成，并增强 PS 诱导的聚合物交联，相应地，也增强了溶液的粘度。由短链表面活性剂和长链表面活性剂组成的 PS 在微观上有所不同，因为前者的极性内部比后者多，这可以从荧光测量中得到证明。本研究表明，较短链表面活性剂倾向于松散地包裹在 PS 内，并允许更大的水渗透，与具有长链表面活性剂的 PS 相比，这会在 PS 内形成相对极性的疏水性核。具有长链表面活性剂的 PS 具有更强的组装性，这是聚合物极性基团和表面活性剂头基之间有利相互作用的结果，这进一步在其水合壳中形成了强氢键结合的水。
