Impact of 2,2,2-trifluoroethanol (TFE) on hydrophobicity enhancement in the aggregation of sodium N-dodecanoyl sarcosinate (SDDS) with nonionic hydroxyethyl cellulose

Abstract

An organic solvent has the ability to improve the extent of hydrophobicity in a mixed polymer-surfactant system. The carbohydrate-based polymers, having spacious applications in food and pharmaceutical industries, can interact effectively with anionic surfactants in a hydrophobic fashion. Over the past few decades, such interaction behaviour has been used in surface modification process in the fields of human health care and cosmetics. This article has been highlighted to gain perception about the effect of ‘cosurfactant’ like organic solvent 2,2,2-trifluoroethanol (TFE) on the self-aggregation of anionic surfactant sodium N-dodecanoyl sarcosinate (SDDS), and its interaction with non-ionic biopolymer hydroxyethyl cellulose (HEC). In this work, the interaction behaviour has been detailed by the use of some conventional methods, such as, tensiometry, conductometry, fluorimetry and microcalorimetry in mixed aquo-alcohol solution. Understanding the binding pattern of the HEC-SDDS system, it appears to be dependent on hydrophobic interaction. From tensiometry, TFE exhibits a fair extent of surface activity and thus, it further enhances the hydrophobicity of the medium. An increased alcohol percentage in the water medium has resulted in a significant reduction in the critical micelle concentration (CMC). TFE promotes micellization of the ionic surfactants at a lower concentration by lowering the charge intensity on the polar head groups of the micelles. Thus, the micellization becomes favoured in TFE solvent. The related thermodynamic and surface parameters have been estimated to get an insight into the bulk and interfacial properties of the anionic amphiphile on the polymeric interface in mixed aquo-alcohol solution. The decreasing trend of aggregation number (NAgg) in TFE solvent has been discussed with the aid of steady state fluorescence spectroscopic technique. Dynamic light scattering (DLS) study has been used for the measurement of hydrodynamic size (Dh) and polydispersity index (PDI) of HEC polymer in the presence of varying percentage of TFE. All these observations have been displayed and explored conceptually and in stepwise fashion. Further, HEC-SDDS aggregate has been visualized from field emission scanning electron microscopy (FESEM) imaging. A striking change in the morphology has been seen in the TFE environment. As an additive, TFE is opted because of its unique properties as a solvent and also vast applications in the field of biological and pharmaceutical industry. The system chosen in this study is completely new in the field of surface chemistry and each of the experimental results provided below is distinct. At higher TFE contents, the micellization of SDDS is not feasible.