Interactional Behavior of Polyelectrolyte Poly Sodium 4-Styrene Sulphonate (NaPSS) with

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1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is the Owner Societies 215 Interactional Behavior of Polyelectrolyte Poly Sodium 4-Styrene Sulphonate (NaPSS) with Imidazolium based Surface Active Ionic Liquids in Aqueous Medium Electronic supporting information Renu Sharma, Ajar Kamal, Tejwant Singh Kang*, Rakesh Kumar Mahajan* * Department of Chemistry, UGC-Centre for Advanced Studies-I, Guru Nanak Dev University, Amritsar-1435, India *To whom correspondence should be addressed: rakesh_chem@yahoo.com; tejwantsinghkang@gmail.com; Fax:

2 Annexure SI Methods (Detailed Description) Surface tension measurements were carried out using Kruss (Hamburg, Germany) Easy dyne tensiometer using ring detachment method at K with an accuracy of ±.15 mn m -1. A mixing time of two minutes followed by an equilibration time of 5 minutes was adopted prior to measurement. Steady-state fluorescence measurements were performed using HITACHI F- 16 Fluorescence Spectrophotometer using a 1 mm path length quartz cuvette at K employing ANS as fluorescent probe. ANS (concentration) was excited at an excitation wavelength of 35 nm and emission spectrum was recorded in the wavelength range of 38 nm using an excitation and emission slit width of 2.5 nm, each. The solution was allowed to equilibrate for 5 minutes to reach the thermal equilibrium after each addition prior to measurement. Conductivity was measured at different temperatures using a digital Systronics conductivity meter model 36 with a dip-type conductivity cell having a cell constant of 1.1 cm - 1. Temperature of the measurement cell was controlled using an Escy IC21 thermostatic bath within the accuracy of ±.1 K. The specific conductivity of deionised double distilled water used in this study was measured to be around 2µS cm -1. Cyclic voltammetric (CV) measurements were carried out on a PC controlled CHI66D (Austin, USA) electrochemical workstation equipped with a conventional three electrode system comprising of a working Pt electrode (2 mm in diameter), a counter Pt wire and a reference Ag/AgCl electrode. All the solutions were deoxygenated with N 2 and working electrodes were polished with slurry of alumina powder. The CV measurements were carried out in the presence of.1 M KCl as a supporting electrolyte. In order to study the interactions between NaPSS and SAILs, successive additions of small aliquots of concentrated SAILs to TEMPO solution (2mM) containing polyelectrolyte have been carried out. The potentiometric measurements were carried out by using an Equiptronics digital potentiometer, Model EQ2 employing the following electrochemical cell assembly: 2

3 Ag/AgCl 3M KCl Test Solution PVC Internal Reference 3M KCl Ag/AgCl membrane Solution The neutral ion-pair complexes of SAILs and sodium dodecylsulfate as C n mim+ds were prepared by the procedure earlier described by us [1, 2]. Equimolar aqueous solutions of (C n mimcl) and sodium dodecylsulfate (SDS) were mixed and after continuous stirring for a considerable time, the white precipitates of C n mim+ds were obtain ed. The precipitates so obtained were washed repeatedly with water to remove NaCl and recrystallized thrice from acetone. The PVC (176 mg), ion-pair (5 mg) and plasticizer (55 mg) were mixed and dissolved in minimum quantity of THF. The resulting mixture was poured in 5-mm petri dish after removing the air-bubbles. The solvent THF was allowed to evaporate at room temperature. The resulting membrane was cut to required size and attached to PVC tubes with PVC glue and equilibrated in 1mM of respective SAIL solution. The internal reference solution was 1mM SAIL in 1mM NaCl. The given composition of the components used for membrane formation represents the best system in terms of slope values, correlation coefficient, linear range and detection limit. The EMF measurements were carried out by titration method at K in the presence of 1mM NaCl solution. Turbidity measurements were performed using Systronics Digital Nepheloturbidity Meter model 132 after equilibrating the solution for 5 minutes. All the measurements were repeated thrice. Dynamic light scattering measurements were performed using a Malvern Nano-ZS Zetasizer instrument employing a He-Ne laser (λ = 632 nm) at a scattering angle of 173 using quartz cuvette having path length of 1 cm. The bare autocorrelation function has been analysed by cumulants fit method. The temperature of the measurement was maintained by built-in temperature controller having an accuracy of ±.1 K. Calorimetric measurements were carried out using MicroCal ITC2 microcalorimeter. The titrations were done by adding 2 µl aliquots of stock solutions of SAILs in 24 µl of aqueous polymer solution using Hamilton syringe. All the measurements were repeated twice. The time of addition and interval between each addition are controlled by software equipped with the instrument. 3

4 Annexure SII. The maximum surface excess concentration (Г max ) and minimum area per molecule [3, 4] at the air-solution interface can be calculated using equation (1) and (2) as follows: d d lnc T nrt max (1) A min =1 2 / (N A. Г max ) (2) The Gibbs free energy of adsorption (ΔG ads ) [5] is calculated using the equation (3) ΔG ads = ΔG mic - П cmc / Г max (3) Annexure SIII The Gibbs free energy of micelle formation, ΔG mic [6] was calculated using the equation (4) ΔG mic = (1+ β) RT ln X cmc (4) Where, β, R, T and X cmc are counter-ion binding, gas constant, temperature on Kelvin scale and cmc expressed in mole fraction. The enthalpy of micelle formation, ΔH mic was calculated by employing Gibbs-Helmholtz equation using free energy of micellization H mic = RT 2 (1 + β) dx cmc dt (5) Then the entropy of micelle formation, ΔS mic is obtained as: S mic H mic G T mic (6) 4

5 Table S1 Interfacial parameters i.e. surface tension at cmc (γ cmc ), effective surface tension reduction (Π cmc ), surface excess (Г max ), minimum area per molecule (A min ), Gibbs free energy of adsorption (ΔG ads ) of SAILs in the absence and presence of polyelectrolyte NaPSS (.2 and ) at K. NaPSS % γ cmc (mn m -1 ) π cmc (mn m -1 ) Γ max 1 6 (mol m -2 ) A min (nm 2 ) ΔG ads kj mol -1 [C 1 mim][cl] [C 12 mim[cl] [C 14 mim][cl] The error estimate in interfacial parameters γ cmc, π cmc, Г max, A min and ΔG ads are ±.1 mn m -1, ±.1 mn m -1, ±.5 mol m -2, ±.5 nm 2 and ±.15 kj mol -1 respectively. 5

6 Table S2 Critical micelle concentration (cmc), counter-ion binding (β), Gibbs free energy of micellization (ΔG m ), enthalpy of micellization (ΔH m ) and entropy of micellization (ΔS m ) of SAILs in aqueous solution at different temperatures. T (K) cmc (mmol dm -3 ) β ΔG m (kj mol -1 ) ΔH m (kj mol -1 ) TΔS m (kj mol -1 ) [C 1 mim][cl] [C 12 mim][cl] [C 14 mim][cl] The error estimate in cmc, β, ΔG m, ΔH m and ΔS m are ±.1 mmol dm -3, ±.2, ±.5 kj mol -1, ±.7 kj mol -1 and ±.13 kj mol -1 respectively. 6

7 Table S3 Critical aggregation concentration (cac), critical micelle concentration (cmc), counterion binding (β), Gibbs free energy of micellization (ΔG m ), enthalpy of micellization (ΔH m ) and entropy of micellization (ΔS m ) of SAILs in NaPSS solution at different temperatures. NaPSS T (K) cac (mmol dm -3 ) cmc β (mmol dm -3 ) [C 1 mim][cl] ΔG m (kj mol -1 ) ΔH m ( kj mol -1 ) TΔS m ( kj mol -1 ) [C 12 mim][cl] [C 14 mim][cl] The error estimate in cac, cmc, β, ΔG m, ΔH m and ΔS m are ±.5 mmol dm -3, ±.1 mmol dm -3, ±.2, ±.5 kj mol -1, ±.7 kj mol -1 and ±.13 kj mol -1 respectively. 7

8 Table S4 Critical aggregation concentration (cac), critical micelle concentration (cmc), counter-ion binding (β), Gibbs free energy of micellization (ΔG m ), enthalpy of micellization (ΔH m ) and entropy of micellization (ΔS m ) of SAILs in NaPSS solution at different temperatures. NaPSS T (K) cac (mmol dm -3 ) cmc β (mmol dm -3 ) [C 1 mim][cl] ΔG m (kj mol -1 ) ΔH m ( kj mol -1 ) TΔS m ( kj mol -1 ) [C 12 mim][cl] [C 14 mim][cl] The error estimate in cac, cmc, β, ΔG m, ΔH m and ΔS m are ±.5 mmol dm -3, ±.1 mmol dm -3, ±.2, ±.5 kj mol -1, ±.7 kj mol -1 and ±.13 kj mol -1 respectively. 8

9 Table S5 Inter-micellar interaction parameter (k d ), self-diffusion coefficient (D m) and diffusion coefficient (D m ) of SAILs in the absence and presence of polyelectrolyte NaPSS (.2 and ). System k d D m D m (M -1 ) (1 5 cm 2 s -1 ) (1 5 cm 2 s -1 ) [C 1 mim][cl] [C 1 mim][cl]+napss () [C 1 mim][cl]+napss () [C 12 mim][cl] [C 12 mim][cl]+napss () [C 12 mim][cl]+napss () [C 14 mim][cl] [C 14 mim][cl]+napss () [C 14 mim][cl]+napss () The error estimate in k d, D m and D m are ±.1 M -1, ± cm 2 s -1 and ± cm 2 s -1 respectively. 9

10 C 1 55 C 1 mn m -1 5 C 3 (C s ) / mn m C 2 (cac) C 3 (C s ) 4 C 4 (cmc) C 2 (cac) 25 C 4 (cmc) log log Fig. S1 Variation of surface tension (γ) as a function of logarithm of concentration of SAILs at.2 and concentrations of NaPSS for [C 12 mim][cl] and [C 14 mim][cl] (c) S cm Fig.S2 Variation of specific conductivity ( ) as a function of concentration of concentration of SAILs in aqueous solution at different temperatures [C 1 mim][cl] [C 12 mim][cl] (c) [C 14 mim][cl]. 1

11 K Fig.S3 Variation of specific conductivity ( ) as a function of concentration of [C 12 mim][cl] in the presence of ; and NaPSS at different temperatures K S cm K Fig. S4 Variation of specific conductivity ( ) as a function of concentration of [C 14 mim][cl] in the presence of ; and NaPSS at different temperatures. 11

12 I/I Turbidity / NTU Turbidity / NTU I/I [C 1 mim][cl] [C 12 mim][cl] [C 14 mim][cl] E-4 1E-3 C / mol dm -3 1E-4 1E-3.1 1E-4 1E-3.1 1E-4 1E-3.1 I/I I/I Turbidity / NTU (c) Fig.S5 Fluorescence intensity of ANS in NaPSS solution as a function of concentration of SAILs. and (c) represents fluorescence intensity of ANS in aqueous and aqueous NaPSS solutions at.2 and concentrations as a function of concentration of [C 12 mim][cl and [C 14 mim][cl]. [C 1 mim][c] [C 12 mim][c] [C 14 mim][c] C 3 (C s ) (c) 3 3 C 3 (C s ) C 2 (cac) C 4 (cmc) 2 C 2 (cac) C 4 (cmc) E Fig.S6. Variation of turbidity versus concentration of three SAILs in polyelectrolyte (NaPSS) solution at a concentration of ; and (c) Variation of turbidity versus concentration of [C 12 mim][cl] and [C 14 mim][cl] at.2 and concentrations of NaPSS. 12

13 % Intensity % Intensity % Intensity 35 5mM 35 5mM mM 4mM 2 2 3mM 3mM mM 2mM 1 14mM 1 14mM 2.2mM 2.2mM 5 5.mM.mM 1 1 D h / nm D h / nm 22 (c) 2 5.mM mM mM 1.5mM 8 1.mM 6.5mM 4 2.mM D h / nm D h / nm 16 (d) [C 1 mim][cl] 1 12 [C 12 mim][cl] [C 14 mim][cl] Fig.S7.Size distribution for concentrations of NaPSS in the presence of increasing concentrations of [C 1 mim][cl], [C 12 mim][cl] and (c) [C 14 mim][cl]. (d) Variation of hydrodynamic diameter (D h ) as a function of concentration of SAILs in NaPSS. 13

14 2 1-2 H / kj mol -1 H / kj mol -1 H / kj mol (c) 1. I II III -4 I II III I II III (d) 6. (e) 11.5 (f) dp / µcal sec dp / µcal sec dp / µcal sec Time / min Time / min Time / min (g) 1. (h) (i) dp / µcal sec dp / µcal sec -1. dp / µcal sec Time / min Time / min Time / min Fig.S8. Calorimetric profiles of SAILs as a function of concentration of [C 1 mim][cl]; [C 12 mim][cl] and (c) [C 14 mim][cl] in the absence and presence of polyelectrolyte, NaPSS (.2 and ) at K. Variation of differential power (dp) versus time for aqueous solution of (d) [C 1 mim][cl] (e) [C 12 mim][cl] (f) [C 14 mim][cl] and for the interaction of NaPSS with SAILs at a concentration of (g) [C 1 mim][cl] (h) [C 12 mim][cl] (i) [C 14 mim][cl]. 14

15 v v EMF / mv EMF / mv.1. C 3 (C 2 ) C 4 (cmc) C 3 (C s ) C 4 (cmc) C 2 (cac) log -.2 C 2 (cac) log Fig.S9 EMF as a function of logarithm of concentration of SAILs in the absence and presence of.2 and NaPSS for [C 12 mim][cl] and [C 14 mim][cl]. 2.x x1 9 3x x x1 9 2x x1 9 I II III 1.x1 9 I II III x log log Fig.S1 Binding isotherms of v versus logarithm of concentration of SAILs in the presence of.2 and NaPSS for [C 12 mim][cl] and [C 14 mim][cl]. 15

16 3.x1 2.5x1 3 i 1 / A P 1.x1 2 2.x1. ip / A 1 1. ip 1 /A ip / A 5.x1 1.5x1 1.x1 5.x C / mol dm x v1/2 / (V s-1)1/ Potential / V Potential / V Fig.S11 Reversible cyclic voltammograms of TEMPO in supporting electrolyte KCl in micellar solution of [C12mim][Cl] at different scan rates in the presence of NaPSS. [Inset of plot shows the variation of ip (A) versus v1/2 for TEMPO ion in aqueous [C12mim][Cl] solution and in the presence of NaPSS Differential pulse voltammograms (DPV) of TEMPO (2mM) in supporting electrolyte KCl (.1 M) for varying concentrations of [C12mim][Cl] in the presence of NaPSS [Inset of plot shows the variation of ip as a function of [C12mim][Cl] in aqueous and aqueous NaPSS solution (.2 and ). 1.2x1 3.x1 2.5x1 3. i 1 / A P 8.x x ip / A ip / A 4.x1 1.5x x1-8.x1 ip 1 /A x1 5.x1.5.1 C / mol dm-3.3 v1/2 / (V s-1)1/ Potential / V Potential / V Fig.S12 Reversible cyclic voltammograms TEMPO (2 mm) in supporting electrolyte KCl (.1 M) in micellar solution of [C14mim][Cl] at different scan rates in the presence of NaPSS [Inset of plot shows the variation of ip (A) versus v1/2 (V s-1)1/2 for TEMPO ion in aqueous [C12mim][Cl] solution and in the presence of NaPSS Differential pulse voltammograms (DPV) of TEMPO (2mM) in supporting electrolyte KCl (.1 M) for varying concentrations of [C14mim][Cl] in the presence of NaPSS [Inset of plot shows the variation of ip as a function of [C14mim][Cl] in aqueous and aqueous NaPSS solution (.2 and ). 16

17 References 1. A. Shaheen, I. Kaur, R.K. Mahajan, Ind. Eng. Chem. Res., 27, 46, R.K. Mahajan, A. Shaheen, J. Colloid Interface Sci., 28, 326, D.K. Chattoraj, K.S. Birdi, Adsorption and Gibbs Surface Excess, Plenum, New York, 1984 (Chapter 3). 4. K. Anand, O.P. Yadav, P.P. Singh, Colloids Surf. A, 1991, 55, P. Mukherjee, Adv. Colloid Interface Sci., 1967, 1, M.J. Rosen, Surfactant and Interfacial Phenomenon, 2 nd edn; John Wiley and Sons: New York,

PCCP PAPER. 1. Introduction. Renu Sharma, Ajar Kamal, Tejwant Singh Kang* and Rakesh Kumar Mahajan* View Article Online View Journal View Issue

PCCP PAPER. 1. Introduction. Renu Sharma, Ajar Kamal, Tejwant Singh Kang* and Rakesh Kumar Mahajan* View Article Online View Journal View Issue PAPER View Article Online View Journal View Issue Cite this: Phys. Chem. Chem. Phys., 2015, 17, 23582 Received 7th May 2015, Accepted 6th August 2015 DOI: 10.1039/c5cp02642c www.rsc.org/pccp 1. Introduction