Colloids and Surfaces A: Physicochem. Eng. Aspects 484 (2015) 547–557 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journa l h om epage: www.elsevier.com/locate/colsurfa Interaction of ionic liquid type cationic surfactants with triton X-100 nonionic micelles Khushbu Thakkar a , Bhavesh Bharatiya b,∗ , Dinesh O. Shah b , Debes Ray c , Vinod K. Aswal c , Pratap Bahadur a a Department of Chemistry, Veer Narmad South Gujarat University, Surat-395007, India b Shah Schulman Center for Surface Science & Nanotechnology, Dharmsinh Desai University, Nadiad-387001, India c Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India h i g h l i g h t s • TX micelles get charged and decrease in size on addition of C n TPPBr. • Strong synergistic interactions depending on alkyl chainlength of cationic surfactant. • Addition of NaBr increases the size of mixed aggregate due to charge neu- tralization. • The mixed micelles transform to extended ellipsoidal shape in aqueous NaBr solutions in 70 mM C 16 TPPBr. • Teflon wettability and foamability of TX-100 solution weakens in presence of C n TPPBr. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 25 June 2015 Received in revised form 19 August 2015 Accepted 21 August 2015 Available online 28 August 2015 Keywords: Interaction parameter Mixed micelles DLS Surface activity Aggregation number a b s t r a c t The aggregation behaviour of alkyl triphenylphosphonium bromide (C n TPPBr, n = 10,12,14,16) in pres- ence of non-ionic Triton X-100 in aqueous solutions is investigated by different analytical techniques viz. surface tensiometry (ST), dye solubilization (DS), cloud point (CP), dynamic light scattering (DLS), zeta potential, small-angle neutron scattering (SANS), contact angle, wettability and foamability measure- ments. The calculated critical micelle concentration (CMC) for aqueous solutions of mixed surfactants is lower than the individual pure surfactants, which confirms the synergistic interactions among the monomers in the formed mixed micelles. On gradual addition of C n TPPBr, the cloud points of TX-100 are shifted to higher temperatures and size of the formed mixed micelles decreases as observed by CP and DLS, respectively. Zeta potential of mixed micelles increases with corresponding increase in the concen- tration of C n TPPBr. Morphological and clouding behaviour of mixed micelles is found to be independent of chainlength for added cationic surfactant, but initial ellipsoidal shape micelles transform to extended ellipsoids in presence of sodium bromide depicting significant increase in the axial ratio. © 2015 Elsevier B.V. All rights reserved. ∗ Corresponding author. Fax: +91 268 2520501. E-mail addresses: khusi1985@yahoo.com (K. Thakkar), bhaveshbharatiya@gmail.com (B. Bharatiya), dineshoshah@yahoo.com (D.O. Shah), debes@barc.gov.in (D. Ray), vkaswal@barc.gov.in (V.K. Aswal), pbahadur2002@yahoo.com (P. Bahadur). http://dx.doi.org/10.1016/j.colsurfa.2015.08.039 0927-7757/© 2015 Elsevier B.V. All rights reserved.