Contents lists available at ScienceDirect Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett Research paper Investigation of physicochemical properties between poly(ethylene glycol)/ poly(vinylpyrrolidone) and 1-butyl-3-methylimidazolium dodecyl sulfate in aqueous solution Amalendu Pal ⁎ , Sangeeta Yadav Department of Chemistry, Kurukshetra University, Kurukshetra 136119, India HIGHLIGHTS • Ion–dipole, hydrogen bonding and hydrophobic interactions exist amid SAIL and polymers. • Three transition stages occurred due complex formation between SAIL and PEG/PVP. • The surface activity of [C 4 mim][C 12 SO 4 ] decreases in presence of PEG/PVP concentrations. • PVP exhibits stronger interaction with [C 4 mim][C 12 SO 4 ] as compared to PEG. ARTICLE INFO Keywords: Poly(vinylpyrrolidone) Poly(ethylene glycol) 1-Butyl-3-methylimidazolium dodecylsulfate Polymer-surface active ionic liquid (SAIL) complexes Surface tension Conductances ABSTRACT In the present communication, the physicochemical properties between an anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecyl sulfate [C 4 mim][C 12 SO 4 ] and nonionic polymers poly(vi- nylpyrrolidone) (PVP)/poly(ethylene glycol) (PEG) have been investigated by conductance and surface tension measurements. From these measurements the critical aggregation concentration (cac), critical micelle con- centration (cmc), and degree of ionization (α) have been estimated. To understand the aggregation and inter- facial behaviour of [C 4 mim][C 12 SO 4 ] towards PVP and PEG, various thermodynamic and surface parameters have also been derived and discussed. The results exhibit that [C 4 mim][C 12 SO 4 ] interacts strongly with PVP as compared to PEG. 1. Introduction The binding interactions between surfactant and polymer have be- come a vital field in colloidal science over the past few decades [1,2]. The surfactant and polymer (water soluble) systems have received an epochal attention by the cause of their wide variety of industrial utili- zations including detergency, paints, cosmetics, oil recovery, pharma- ceuticals, and formulation of pesticides etc. [3–6]. The understanding of existing interactions between the oppositely charged polymer and ionic surfactants is comparatively easy [7,8]. However, the situation becomes relatively intriguing and complex while discussing ionic surfactant and nonionic polymers such as poly(ethylene glycol) (PEG) and poly- vinylpyrrolidone (PVP). For this type of systems, a variety of factors such as surfactant head group, polar segments on polymer, hydro- phobicity and flexibility [9–13] of surfactant govern the interactions prevailing among ionic surfactant and ionic/nonionic polymer which makes the overall understanding relatively complex. Also, the fact that nonionic polymers have stronger affinity for anionic surfactants as compared to cationic surfactants has been well established [14,15]. Ionic liquids (ILs) are defined as molten salts consisting of large asymmetric organic cation and organic/inorganic anion having melting point less than 100 °C. The unique physicochemical properties of ILs such as low bioaccumulation, low volatility, wide electrochemical window, high thermal stability, high ionic conductivity, designer nature, negligible vapor pressure, remarkable solvation abilities, good recyclability [16,17], extraction and separation, organic synthesis, biocatalysts and lubricants [18–20], exhibit low toxicity, antimicrobial activity [21,22] attracted the attention of many research groups. Fur- ther, most of these ILs possess long hydrophobic/amphiphilic alkyl chain and form micelles with large range of critical micelle con- centration (cmc). These types of ILs are surface active in nature and hence also known as surface active ionic liquids (SAILs). The amphi- philicity of these types of ionic liquids can be tailored by altering the length of the hydrophobic chain. The depictions of SAILs in the https://doi.org/10.1016/j.cplett.2018.10.055 Received 15 July 2018; Received in revised form 21 October 2018; Accepted 22 October 2018 ⁎ Corresponding author. E-mail address: palchem21@gmail.com (A. Pal). Chemical Physics Letters 714 (2019) 45–52 Available online 24 October 2018 0009-2614/ © 2018 Elsevier B.V. All rights reserved. T