Fajalia Ankitkumar I, Alexandridis Paschalis, Tsianou Marina
Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York (SUNY), Buffalo, New York 14260-4200, United States.
Langmuir. 2023 Aug 22;39(33):11529-11544. doi: 10.1021/acs.langmuir.3c00712. Epub 2023 Aug 11.
Polysaccharides and their derivatives are commonly used in pharmaceutical and agricultural formulations as rheology modifiers. Their performance is related to their conformation in solution, which in turn is affected by other ingredients present in the formulation. This study focuses on modulating the conformation of relatively rigid cellulose chains in aqueous solutions. In particular, we have investigated the nonionic cellulose derivative ethyl(hydroxyethyl)cellulose (EHEC) in water in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and/or ethanol acting as modulating agents. We have used small angle neutron scattering (SANS) with contrast variation to determine the EHEC chain conformation in the presence of (but not masked by) ethanol and SDS. In dilute and semidilute aqueous solutions, EHEC exhibits worm-like chain conformation due to the rigid cellulose backbone. Addition of ethanol does not impact the polymer conformation to a great extent. Addition of SDS alters the EHEC chain conformation, resulting in polyelectrolyte-like scattering behavior due to repulsive interactions between bound charged micelles which show similar structure as the free SDS micelles in solution (in the absence of polymers). Ethanol affects the polymer + surfactant system primarily by acting on the surfactant (bound on polymer) which, in turn, affects the polymer conformation. At higher ethanol concentrations (20 wt %), EHEC regains the worm-like chain conformation because of the detachment of the bound SDS micelles. To the best of our knowledge, this is the only study providing details on chain conformation of the rigid polymer EHEC in dilute or semidilute aqueous solutions in the presence of surfactant and alcohol and one of very few papers utilizing SANS for the characterization of polymer + surfactant + water + alcohol interactions. Such fundamental understanding of interactions and structure in multicomponent mixtures supports the design of industrial formulations.
多糖及其衍生物通常作为流变改性剂用于药物和农业配方中。它们的性能与其在溶液中的构象有关，而构象又受到配方中其他成分的影响。本研究聚焦于调节水溶液中相对刚性的纤维素链的构象。具体而言，我们研究了在离子表面活性剂十二烷基硫酸钠（SDS）和/或作为调节剂的乙醇存在下，非离子纤维素衍生物乙基（羟乙基）纤维素（EHEC）在水中的情况。我们使用了具有对比变化的小角中子散射（SANS）来确定在有乙醇和SDS（但未被其掩盖）存在时EHEC链的构象。在稀溶液和半稀溶液中，由于刚性的纤维素主链，EHEC呈现蠕虫状链构象。添加乙醇在很大程度上不会影响聚合物构象。添加SDS会改变EHEC链的构象，由于结合的带电胶束之间的排斥相互作用，导致类似聚电解质的散射行为，这些胶束在溶液中（不存在聚合物时）与游离的SDS胶束具有相似的结构。乙醇主要通过作用于（结合在聚合物上的）表面活性剂来影响聚合物 + 表面活性剂体系，进而影响聚合物构象。在较高乙醇浓度（20 wt%）下，由于结合的SDS胶束的脱离，EHEC恢复了蠕虫状链构象。据我们所知，这是唯一一项提供关于刚性聚合物EHEC在表面活性剂和醇存在下的稀溶液或半稀溶液中链构象细节的研究，也是利用SANS表征聚合物 + 表面活性剂 + 水 + 醇相互作用的极少数论文之一。对多组分混合物中相互作用和结构的这种基本理解有助于工业配方的设计。
