Influence of polyethylene glycol on the aggregation/clouding phenomena of cationic and non-ionic surfactants in attendance of electrolytes (NaCl & Na 2 SO 4 ): An experimental and theoretical analysis Shahina Aktar a , Mousumi Saha b , Shamim Mahbub a,c , Mohammad A. Halim b,d , Malik Abdul Rub e,f , Md. Anamul Hoque a, ⁎, D.M. Shafiqul Islam a, ⁎, Dileep Kumar g,h, ⁎⁎, Yousef G. Alghamdi e , Abdullah M. Asiri e,f a Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh b Division of Quantum Chemistry, The Red-Green Research Centre, BICCB, 16, Tejkunipara, Tejgaon, Dhaka 1215, Bangladesh c Department of Chemistry & Physics, Gono Bishwabidyalay, Savar, Dhaka 1344, Bangladesh d Department of Physical Sciences, University of Arkansas-Fort Smith, Fort Smith, AR 72903, USA e Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia f Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia g Division of Computational Physics, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Viet Nam h Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Viet Nam abstract article info Article history: Received 20 January 2020 Received in revised form 9 March 2020 Accepted 10 March 2020 Available online 13 March 2020 Keywords: Polyethylene glycol 400 Surfactants Cloud point cmc Thermodynamic parameters Herein, multiple techniques were employed to gain an accurate and deep understanding for the interaction be- tween synthetic polymer polyethylene glycol 400 (PEG 400) and surfactant (TTAB/Triton X-100 (TX-100)) in electrolytes or electrolytes free medium. Critical micelle concentration (cmc) and extent of counterion binding (β) over the 298.15 to 318.15 K temperature range were determined and thereby the degree of interaction be- tween PEG 400 and TTAB has been estimated. The cmc of pure TTAB in H 2 O exhibits U-like variation with the es- calation of temperature. Assessed cmc values of TTAB/TTAB + PEG 400 mixture in water as well as in NaCl solution enhance monotonically with temperature. The cmc values of TTAB + PEG 400 mixture in Na 2 SO 4 solu- tion exhibit reversed U-shaped variation with escalation of temperature. Estimated cmc values of TTAB + PEG 400 mixture in occurrence of NaCl/Na 2 SO 4 were decreased in comparison to aqueous medium while at a fixed concentration of salts and particular temperature the magnitudes follow the order: cmc NaCl N cmc Na2SO4 . The es- timated values of Gibbs free energy (ΔG m o ) & enthalpy (ΔH m o ) of micellization were negative almost in each case. The values of ΔH m o and ΔS m o indicate the presence of both hydrophobic & electrostatic interactions between PEG 400 and TTAB. Executed CP of TX-100 was reduced in the existence of PEG 400 almost in each case. The values of Gibbs free energy of clouding (ΔG c o ) were positive in all cases. The entropy-enthalpy compensation was observed both for aggregation of TTAB and clouding of TX-100. The atomic level interacting mechanism of PEG 400- surfactant system in salt and aqueous environment was disclosed by means of molecular dynamics simulation, which showed a good agreement with the experimental results. © 2020 Published by Elsevier B.V. 1. Introduction The inspection of the interaction of dyes/drugs/polymers with am- phiphilic substance became interesting to the researchers in last few de- cades due to having large applications of amphiphilic substances fundamental as well as in technical areas. The presence of both polar and apolar parts in the molecular structure of amphiphilic substances is responsible for self-assembled structure of the amphiphilic substance which is outcome of balanced interaction of opposite parts of the surfac- tants with the solvent [1–3]. The aforementioned self-assembled struc- ture of the amphiphilic substance is termed as micelles and micelles appear when surfactant concentration reaches to a certain value called cmc [1–3]. The micelles of surfactants can be assumed as model biolog- ical membranes due to having similar structure. The application of sur- factants/amphiphiles critically depend on their complex formation through different solutes like drugs, polymers, dyes and other micro-/ macro-molecules [1–7]. Micelles incorporate the feebly soluble organic entities (polymer/drug) in the hydrophobic core of the micelles conse- quently increase the solubility/bioavailability of these organic species [8,9]. The inclusion of any second solute to the surfactant solutions Journal of Molecular Liquids 306 (2020) 112880 ⁎ Corresponding authors. ⁎⁎ Correspondence to: D. Kumar, Division of Computational Physics, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Viet Nam. E-mail addresses: ahoque_ju@yahoo.com (M.A. Hoque), dmshafiq@yahoo.com (D.M.S. Islam), dileepkumar@tdtu.edu.vn (D. Kumar). https://doi.org/10.1016/j.molliq.2020.112880 0167-7322/© 2020 Published by Elsevier B.V. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq