Synthesis, characterization and mixed micellization study of benzene sulphonate based gemini surfactant with sodium dodecyl sulphate

Article abstract of DOI:10.1016/j.molliq.2019.04.057

Herein, we have shown the mixed micelle formation between anionic benzene sulphonate (viz., sodium 4,4′-(16,25-dioxo-15,17,24,26-tetraaza-hexatriacontane15,26-diyl)dibenzenesulphonate [BSC14-C6-14CSB]and sodium 4,4′-(18,27-dioxo-17,19,26,28-tetraaza-tetracontane15,26-diyl)dibenzenesulphonate [BSC16-C6-16CSB])with conventional anionic surfactant (sodium dodecyl sulphate [SDS])by conductivity and fluorometry methods. The conductivity measurements were done over a range of mole fractions of SDS at different temperatures to study the mixed micellization and thermodynamic parameters, while fluorescence measurements were performed over entire range of mole fraction of SDS in order to observe the aggregation and micro-polarity. The conductometric study confirms the synergism in all mole fractions of SDS with [BSC14-C6-14CSB]and [BSC16-C6-16CSB]at all temperatures. The Rubinghs regular solution theory (RST)was employed to evaluate micellar mole fraction, X₁, ideal micellar mole fraction, X^ideal, interaction parameter (β), activity coefficients (f₁, and f₂)for both mixed micelles systems and Gibbs excess free energy (G^E). The G^E values are negative for entire mole fraction range suggesting the formation of stable mixed micelles. In addition to this, other thermodynamic parameters like Gibbs free energy change of micellization (ΔG_mic), enthalpy change of micellization (ΔH_mic)and entropy change of micellization (ΔS_mic)were evaluated. Also, the aggregation number (N_agg)in micelles was calculated using pyrene probe fluorescence measurement. The binding constant, dielectric constant and micropolarity of mixed systems of SDS + [BSC14-C6-14CSB]and SDS + [BSC16-C6-16CSB]binary mixtures were obtained from the ratio of peak strength (I₁/I₃)from the pyrene probe fluorescence emission spectra.

Full text of DOI:10.1016/j.molliq.2019.04.057

Accepted Manuscript
Synthesis, characterization and mixed micellization study of
benzene sulphonate based gemini surfactant with sodium dodecyl
sulphate
Farooq Ahmad Wani, Abbul Bashar Khan, Abdulmohseen Ali
Alshehri, Maqsood Ahmad Malik, Rabia Ahmad, Rajan Patel
PII:
S0167-7322(19)30850-5
DOI:
Reference:
https://doi.org/10.1016/j.molliq.2019.04.057
MOLLIQ 10780
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
13 February 2019
10 April 2019
11 April 2019
Please cite this article as: F.A. Wani, A.B. Khan, A.A. Alshehri, et al., Synthesis,
characterization and mixed micellization study of benzene sulphonate based gemini
surfactant with sodium dodecyl sulphate, Journal of Molecular Liquids, https://doi.org/
10.1016/j.molliq.2019.04.057
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ACCEPTED MANUSCRIPT
Synthesis, characterization and mixed micellization study of benzene sulphonate based
gemini surfactant with sodium dodecyl sulphate
Farooq Ahmad Waniac, Abbul Bashar Khanac, Abdulmohseen Ali Alshehrib, Maqsood Ahmad
Malikb, Rabia Ahmadc*, Rajan Patela*
aBiophysical Chemistry Laboratory, Centre for Interdisciplinary Research in Basic Sciences,
Jamia Millia Islamia (A Central University), New Delhi
bSurface Chemistry and Catalytic Studies group, SCCS, Department of Chemistry, King
Abdulaziz University, Jeddah-21589, Saudi Arabia.
cDepartment of Chemistry Jamia Millia Islamia (A Central University), New Delhi.
*Corresponding author.
Tel.: +91 8860634100; fax: +91 11 26983409.
Email address: rpatel@jmi.ac.in, (Dr. R. Patel), rahmad@jmi.ac.in (Prof. Rabia Ahmad)
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Abstract:
“Herein, we have shown the mixed micelle formation between anionic benzene sulphonate
(viz.,sodium4,4′-(16,25-dioxo-15,17,24,26-tetraaza-hexatriacontane15,26-diyl)
dibenzenesulphonate [BSC14-C6-14CSB] and sodium 4,4′-(18,27-dioxo-17,19,26,28-
tetraaza-tetracontane15,26-diyl)
dibenzenesulphonate
[BSC16-C6-16CSB])
with
conventional anionic surfactant (sodium dodecyl sulphate [SDS]) by conductivity and
fluorometry methods. The conductivity measurements were done over a range of mole
fractions of SDS at different temperatures to study the mixed micellization and
thermodynamic parameters, while fluorescence measurements were performed over entire
range of mole fraction of SDS in order to observe the aggregation and micro-polarity. The
conductometric study confirms the synergism in all mole fractions of SDS with [BSC14-C6-
14CSB] and [BSC16-C6-16CSB] at all temperatures. The Rubinghs regular solution theory
(RST) was employed to evaluate micellar mole fraction, X1, ideal micellar mole fraction, Xideal
,
interaction parameter (β), activity coefficients (f1, and f2) for both mixed micelles systems
and Gibbs excess free energy (GE). The GE values are negative for entire mole fraction range
suggesting the formation of stable mixed micelles. In addition to this, other thermodynamic
parameters like Gibbs free energy change of micellization (∆Gmic), enthalpy change of
micellization (∆Hmic) and entropy change of micellization (∆Smic) were evaluated. Also, the
aggregation number (Nagg) in micelles was calculated using pyrene probe fluorescence
measurement. The binding constant, dielectric constant and micropolarity of mixed systems
of SDS+ [BSC14-C6-14CSB] and SDS+ [BSC16-C6-16CSB] binary mixtures were obtained
from the ratio of peak strength (I1/I3) from the pyrene probe fluorescence emission spectra.
Keywords: Gemini Surfactants; SDS; Fluorescence; Mixed micelles; Synergism;
Aggregation number
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1. Introduction
Amphiphiles having a polar hydrophilic head group and a stretchy hydrophobic hydrocarbon
chain which on impulse forms aggregates in aqueous solution results in a supra-molecular
assemblies simply known as micelles at a definite concentration called critical micelle
concentration (cmc)[1, 2]. This amphiphilic nature of such molecules is accountable for their
distinctive properties like self-aggregation, adsorption at the interfaces and dissolving of
hydrophobic molecules that are responsible for their extensive utilize in the food,
pharmaceutical, petrochemical, agrochemical, textile, paint and coating industries as wetting
and foaming agents, emulsifying and suspension stabilizers[3]. The amphiphilic compounds
have a unique feature of self-aggregation forming micelles that result due to the hydrophobic
attraction by hydrocarbon chains of tail and electrostatic repulsion of hydrophilic groups[2, 4-
7]. They have a unique property such as cmc, a necessary criteria for micelle formation to be
used in drug delivery systems. The surfactants are usual amphiphiles having two core parts
i.e., the hydrophilic part providing a highly polarized environment and other is the
hydrophobic part that provides a low polarity environment[8]. These two regions are able to
encapsulate drugs by improving their solubility, bioavailability and also shields them from
harsh factors on parenteral administration[9]. Some physicochemical properties of gemini
surfactants such as high surface activity, low cmc, better wetting and foaming ability, and
high solubility are much better than conventional surfactants[10]. The two head groups and
two hydrophobic hydrocarbon tails are joined by a rigid or flexible spacer [11, 12] have
attracted great attention due to their unique dimeric structural design that renders their
properties, especially higher effectiveness in reducing surface tension and low cmc values
compared to their monomeric counterparts[13-23]. They can be used as templates for
nanoparticles and biomembrane model systems as capable drug delivery as well as
transfecting agents [12, 24-26]. In recent times, the examination and synthesis of numerous
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new classes of gemini surfactant (cationic/anionic surfactants) has been reported like
imidazolium[27-29], pyridinium[30, 31], pyrrolidinium[32], piperidinium[33], amino acid
based[34], benzene sulphonate based[35] etc. These surfactants were able to interact with
biological (macro) molecules, like serum albumin proteins, membrane lipids and macro
cyclic oligosaccharides [36-45]. Great work has been reported on mixed micellization of
anionic gemini surfactants with different additives like Kazuyuki et al has observed the
interaction between two anionic gemini surfactants having N,N-dialkylamide and carboxylate
groups in the molecule with anionic surfactants in 0.1 M NaCl at pH 5.0 [46]. Luis et al. has
observed the mixed micellization between anionic amino acid based surfactants and bile salts
[47]. Siddiqui et al. studied the mixed micellization of G5 gemini surfactants with
conventional surfactants like SDS, CTAB and Brij35[48].
In this work, we report the synthesis and characterization of two anionic gemini surfactants,
[BSC14-C6-14CSB] and [BSC16-C6-16CSB] having benzene sulphonate head groups with
different chain lengths. Further, this paper highlights the mixed micellization of these gemini
surfactants with conventional surfactant SDS in aqueous solution. The mixed micellization
was studied by employing conductivity measurements and were further supported by
fluorescence studies. The purpose of this study is to get an insight into the relative interaction
of the synthesized gemini surfactants having dissimilar hydrophobic moiety but has same
electrical charged head group with SDS.
2. Materials and Methods
2.1. Materials.
Lauric acid (>99.1% purity) Sigma Aldrich USA, chlorosulphonic acid (>98% purity, AR)
Sigma Aldrich USA, thionyl chloride (>99% purity, AR), aniline (>97.5% purity, AR),
lithium aluminium hydride ( ≥ 96% purity were purchased from Merck India, 1, 6-
hexamethylene diisocyanate (≥99% purity, GC) Sigma Aldrich USA and SDS (≥99% purity,
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AR) Sigma Aldrich USA. All other reagents were used without additional purification. Milli
Q water having specific conductivity < 1.4 µS cm-1 was used in all experiments.
2.2. Synthesis of anionic gemini surfactants
Step I. Synthesis of N-phenyl myristamide
Myristic acid (0.10mol, 22.8g) was added to 100ml of thionyl chloride. The solution was
stirred at 323.15 K for about 40 minutes and then at 363.15 K for another 3 hours. The excess
thionyl chloride was removed by distillation to give myristoyl chloride (0.07mol, 17.2g).
Aniline (0.04mol, 3.7ml) and triethylamine (24 ml) were dissolved in DCM (120ml), the
stirred solution was cooled to 273.15 K in an ice bath and myristoyl chloride (0.07mol, 17g)
was added in drop wise manner to the stirred solution under nitrogen environment. The
reaction was continued for 48 hours at room temperature. Then the reaction mixture was
transferred to a separating funnel followed by washing with water (200ml) and water layer
was extracted twice with DCM. Finally, product was washed with brine and then dried with
sodium sulphate anhydrous. The compound was checked by running column chromatography
and crude product was purifying via recrystallization in hexane to give white solid as N-
phenyl myristamide (yield 85%).
Step II. Synthesis of N- tetradecyl aniline
To a stirred solution of lithium aluminium hydride (0.04 mol, 1.51g) in tetrahydrofuran
anhydrous (35 ml), N- phenyl myristamide (0.02mol, 6.06g) separately dissolved in
tetrahydrofuran (35 ml) were added drop wise under nitrogen environment. The mixture was
heated at reflux for 8 hours followed by cooling to 273.15K. Water was added to quench the
reaction and the mixture was stirred for another 1 hour. The white precipitate was removed
by filtration and filtrate was dried sodium sulphate anhydrous and then filtered and
concentrated. The crude product was purified by running the column chromatography with n-
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hexane ethyl acetate (10:2) as an eluent. The N-tetradecyl aniline was obtained as pale white
solid (yield 78%).
Step III. Synthesis of precursor (hexane1, 6 diyl- bis 3, 3 tetradecyl phenyl urea)
Hexamethylene diisocyanate (0.01mol, 1.68ml) was added to stirred solution of N-
tetradecylaniline (0.017mol, 5.05g) in 25ml DCM. The mixture was stirred over night at
room temperature. After the evaporation of the solvent, the crude product was purified by
running column chromatography with petroleum ether, ethyl acetate as an eluent. The product
was further purified by recrystallization in ether to give greenish white powder (yield 82%).
Step IV. Synthesis of the surfactant I [BSC14-C6-14CSB]
◦
The precursor (0.003mol, 2.24g) was cooled to 0 C. under nitrogen environment and
chlorosulphonic acid (0.0125mol, 1.45ml) was added and mixture was kept undisturbed for 3
hours. Then the mixture was poured in to 25ml ice cold water and pH of solution was
maintained at 7.0 by adding sodium hydroxide (1M). After the solvent evaporation a pale-
yellow residue was desalted in methanol. Finally, the product was purifying through column
chromatography with DCM, methanol (4:1) as an eluent. The Surfactant I was obtained as a
white solid (with yield 81%) shown in schame1.
sodium4,4′-(16,25-dioxo-15,17,24,26-tetraaza-hexatriacontane15,26-diyl)
dibenzenesulphonate
Scheme: 1 Synthesis of [BSC14-C6-14CSB]
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(Synthesis of surfactant II was same but palmic acid is taken in place of myristic acid)
2.3. Methods
2.3.1. Conductivity measurements
Eutech Con 700 conductometer with a cell constant 1.002 ± 0.001 µScm−1 was utilized to
monitor the specific conductance of the surfactant solutions after appropriate mixing. 13 mL
of water (milli Q) was taken in a glass tube in which cell is immersed and glass tube is
immersed in a thermostatic water bath Grant GD120 with temperature constancy of ±0.01 °C
to maintain the temperature. The specific conductivity of milli Q water is 1.80 μS/cm
measured at 25 °C. The reading was noted after every adding of pure anionic gemini
surfactant, and its binary solution with SDS in the mole fractions of 0.1 to 0.9 mol/kg
solution at various temperatures and plots of specific conductivity versus molar concentration
were drawn in origin.
2.3.2. Fluorescence
Cary Eclipse fluorescence spectrometer (Agilent Technologies) with 1cm quartz cuvette path
length has been used to perform fluorescence measurements. The instrument is equipped with
xenon lamp 150W. The excitation wavelength was set at 335nm, and emission wavelength
range was selected from 345 to 600 nm with a slit width of 5nm respectively. The pyrene was
used as external probe and benzoquinone as quencher. Throughout measurements, the pyrene
concentration was constant at 1µM.[49]
3. RESULTS AND DISCUSSION
3.1. Characterization
The two anionic gemini surfactants, i.e. [BSC14-C6-14CSB] and [BSC16-C6-16CSB] were
1
characterized by FT-IR, H NMR and mass spectroscopy (see Figures: S1-S3). The spectral
results are given below
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1.
Sodium
4,4′-(16,25-dioxo-15,17,24,26-tetraaza-hexatriacontane15,26-diyl)
dibenzenesulphonate [BSC14-C6-14CSB].
(i) FT-IR (4000-600cm-1ATR tablet) 3341cm-1 [υ(N-H)], 2907cm-1 [υ(CH3)], 2848cm-1
[υ(CH2)], 1626cm-1[υ(C=O)], 1567cm-1 [υ(N-H bending)], 1442cm-1[υ (C-N bending)],
1397cm-1 [υ (C-C bending)], 1238cm-1 [υAs (SO2)], 1093cm-1[υS (SO2)], and 602 cm-1 [υ (C-H
in plane bending )].
1
(ii) HNMR Bruker Avance II 400 MHz (DMSO) δ= 0.87ppm (t, 6H), 1.25ppm (m, 48H),
2.58ppm (m, 8H), 3ppm (t, 2H attached to nitrogen), 7.6ppm (s, for aromatic hydrogen’s).
(iii) ESI–MS (HP1100LC–MSD): [C48H80N4O8S2Na]+: calcd: 944, found 939.8,
[C35H53N4O8S2Na]: calcd: 767, observed 770, [C37H38N2O4SNa]+: calcd: 435, observed: 441,
[C9H8N2O4SNa].+: calcd: 252, observed: 257, [C7H4NO4SNa]: calcd: 222, observed: 227.3,
[C13H27]: calcd: 181, observed: 179.1.
2.
Sodium
4,4′-(18,27-dioxo-17,19,26,28-tetraaza-tetracontane15,26-diyl)
dibenzenesulphonate [BSC16-C6-16CSB].
(i) FT-IR (4000-600cm-1ATR tablet) 3334cm-1 [ υ(N-H) ], 2907cm-1 [υ(CH3)], 2853cm-1
[υ(CH2)], 1619cm-1[υ(C=O)], 1573cm-1 [υ(N-H bending)], 1476cm-1[υ (C-N bending)],
1370cm-1 [υ( C-C bending)], 1252cm-1[υA (SO2)], 1100cm-1 [υS (SO2)], and 608cm-1 [υ (in
plane C-H bending )].
1
(ii) HNMR Bruker Avance II 400 MHz (DMSO) δ= 0.91ppm (t, 6H), 1.25ppm (m, 52H),
2.59ppm (m, 8H), 2.61ppm (s, 2H attached to nitrogen), 7.39ppm (s, for aromatic
hydrogen’s).
(iii) ESI–MS (HP1100LC–MSD): [C50H84N4O8S2Na]+: calcd: 972, observed: 996,
[C36H55N4O8S2Na]: calcd: 782, observed: 780.5, [C37H38N2O4SNa]+: calcd: 449, observed
450.7, [C9H8N2O4SNa].+: calcd: 251, observed: 249, [C7H4NO4SNa]: calcd: 221, observed:
220.9, [C13H27]: calcd: 211.1, observed: 211.1.
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3.2. Mixed micellization
The mixed micellization of [BSC14-C6-14CSB] and [BSC16-C6-16CSB] with SDS was
observed by conductivity method. The specific conductivity values of gemini surfactant
[BSC14-C6-14CSB] and [BSC16-C6-16CSB] with SDS enhanced linearly with the
increasing concentration of gemini surfactant in the bulk till a split point is reached at the cmc
and then further increases with a reduced slope at higher concentration. The lesser slope
beyond cmc is due to the reduced mobility of the micelles as that of the free surfactant
monomers. The g values of [BSC14-C6-14CSB] are smaller than that of [BSC16-C6-
16CSB], which is due to the more hydration of former ion than the latter, which gets weakly
adsorbed on the micellar surface. The cmc value of both the gemini surfactants and pure SDS
increase slightly with increase in temperature (Figure: 1), that may be ascribed due to the
increased thermal molecular motion, which results from the long-lasting spatial distance and
weak interactions between the hydrophobic chains of the surfactants. Thus, enough surfactant
concentration is required to form the micelles at higher temperature. Moreover, the value of
cmc at a particular temperature lowers with enhance in the gemini surfactant chain length
revealing that the hydrophobic alkyl chain has high effect on the gemini surfactant
micellization and is in good harmony with the results reported previously [50, 51]. The
increase in temperature can speed up the motion of molecules and ions in the solution and
gives favourable environment to the counter ions to separate from the electrostatic repulsion
of the micelles, As a consequence of this, the degree of dissociation (g) increases with the
increase in temperature as given in Table S1. It is also observed that g value of the [BSC14-
C6-14CSB] is slightly smaller than those of [BSC16-C6-16CSB] with the identical spacer
length. Further, the value lowers with the reduction of the chain length, which is mainly due
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to the change in the charged surface density of the micelles. The two anionic head groups of
the gemini surfactant [BSC14-C6-14CSB] and [BSC16-C6-16CSB] are bonded collectively
by the linker by a covalent bond and gets more closely packed when the length of spacer gets
shorter and helps to increase the charge density of hydrophilic head group. Thus, the
electrostatic interaction among the surfactant ions and counter ions gets stronger and the
degree of dissociation (g) is reduced significantly. The micelles are not considered as good
charge carriers due to their low mobility, because they have more weight and hydrodynamic
radius which reflects the degree of counter-ion binding with negatively charged micelle
surface [52, 53]. The values of cmc for each surfactant mixture were evaluated from
breakpoint in the plot of specific conductivity vs. surfactant concentration as reported in
literature [54] (Figure: S4, Figure: S5). The cmc values of all the mole fractions of SDS with
gemini surfactant increases up to certain temperature (308.15 K) and then decreases. The
degree of dissociation (g) has been obtained from the ratio of the slopes in the post and pre-
micellar regions of the specific conductivity vs. concentration of surfactant. The degree of
counter ion binding was evaluated by the following equation [55].
(1)
  (1 g)
where g is degree of dissociation, the exactness of cmc determination of the specific
conductivity vs. concentration of surfactant profile depends upon an unexpected change of
conductivity of the pre and post cmc values[56], that is observed in all binary systems and
also for pure SDS and gemini surfactant [BSC14-C6-14CSB]/ [BSC16-C6-16CSB]. The cmc
generally defines very supportive nature of the aggregation process of both gemini and
conventional amphiphiles determined from conductivity measurements (Table 2) and be in
good agreement with each other. The cmc obtained by conductivity measurements were used
for further calculations like, Xideal, β, X1 etc. Different mole fractions of SDS (α =0.1, 0.3, 0.5,
0.7, 0.9) were taken and gemini surfactant concentrations was kept as 30 µM for all the mole
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fractions. The pseudo phase models were used to examine the properties of ideal or non-ideal
behaviour of mixed micelles of SDS+[BSC14-C6-14CSB] and SDS+[BSC16-C6-16CSB]
accordingly. The micelles are thought to be a macroscopic phase and are in equilibrium
through their subsequent monomers in a solutions[57]. The values of cmc for the binary
systems are found to vary as its ideal mixing behaviour evaluated by the Clint equation[58].
S
(1S )
cmcG
1


(2)
cmc cmcS
where αS represents mole fraction of the SDS in the bulk, cmcG and cmcS are the micellar
concentrations of [BSC14-C6-14CSB]/ [BSC16-C6-16CSB] and SDS correspondingly and
cmc* is the critical micelle concentration of the mixture under ideal mixing states. The Clint
model is reliable through a pseudo phase thermodynamic approach[58], that grants the
calculation of the micellar mole fraction of the gemini surfactants [BSC14-C6-
14CSB]/[BSC16-C6-16CSB] in the ideal state
S cmcG
S cmcG  (1S )cmcS
X ideal

(3)
The cmc ideal (Xideal) values obtained from Clint Model, experimental cmc value and mole
fraction of the SDS in the mixed micelle evaluated by ideal mixing behaviour are given Table
1. The Xideal values of SDS with [BSC14-C6-14CSB]/[BSC16-C6-16CSB] predicted by the
Clint model reveals non-ideal mixing behaviour due to synergism among the dissimilar
amphiphiles in the mixed micelles[59]. These values increase with increasing temperature for
all mole fractions. The Rubingh regular solution theory (RST) [59, 60] was applied to binary
mixtures in non-ideal state in surfactants with great success, because of its simple approach.
The type of interactions in mixed micelle between two surfactant species is confirmed by a
dimensionless parameter β. The β can be calculated from equation: 4.
ln(S cmcmix X1cmcS )
 
(4)
(1 X1 )2
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Here the cmcmix is the experimental cmc of SDS+[BSC14-C6-14CSB] and SDS+[BSC16-C6-
16CSB] mixture and X1 is the mole fraction of the SDS in the mixed micelle and can be
evaluated from equation: 5.
X12 ln(S cmcmix X1cmcS )
 1
(5)
(1 X1 )2 ln (1 X1 )2 ln[(1 X S )cmcmix (1 X1 )cmcG ]
The Gibbs excess free energy (GE) was evaluated from
GE  xS xG RT
(6)
where β represents interaction, parameter obtained by equation: 4, xS and xG stands for the
mole fractions of conventional surfactant (SDS) and gemini surfactants [BSC14-C6-
14CSB]/[BSC16-C6-16CSB] correspondingly, R represents gas constant and T absolute
temperature. The X1, β, GE were calculated by means of regular solution theory for binary
solutions of [BSC14-C6-14CSB]/[BSC16-C6-16CSB] surfactants and are given in Table 1.
The value of X1 increase with rising of mole fraction and shows a uniform trend with
increasing temperature, which suggests formation of mixed micelle between gemini
surfactants and SDS is favoured and additional molecules of SDS put in to the mixed micelle
formation. Also, Xideal enhances with rising of mole fraction at all temperature. The values of
Xideal are greater than X1 revealing that the mixed micelle contains enough SDS monomers as
compared to the mixed ideal state. The type of interaction in mixed micelles among the
components can be studied by using interaction parameter β. The negative value of β reveals
synergism and positive value indicates antagonism, which arises due to the attractive or
repulsive interactions among the amphiphiles in the supra molecular mixed aggregates[60].
Generally β with negative value reveals a synergistic interaction, which means that in mixing
there is a strong attraction among the components than before mixing[54]. Whereas β with
positive value means antagonism is the case of weak interaction and zero value demonstrate
no interaction[61, 62]. The experimental values of β for the mixed systems of SDS with
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[BSC14-C6-14CSB]/[BSC16-C6-16CSB] are negative for entire range of mole fractions at
all temperatures. The synergism in the formation of mixed micelles of [BSC14-C6-
14CSB]/[BSC16-C6-16CSB] gemini surfactant rich composition arises due to a combined
effects of existing hydrophobic interactions between the gemini surfactant chains and the
hydrophobic conventional surfactants chains with some hydrogen bonding in the mixed
micelles[63, 64].
The β have to be constant above a certain composition range as per regular solution theory for
most of the non-ionic surfactants mixtures. Though, for various ionic surfactant binary
combinations, variation of β with composition is repeatedly observed. The huge differences
in surfactant head group size and hydrophobic tail has been reported as composition-
dependent interaction parameter, but RST does not acquire the consideration of size or shape
of the supra molecular aggregates [65-67]. The interaction of the SDS with [BSC14-C6-
14CSB] gemini surfactant mixtures is synergistic type and increases with increasing mole
fraction. This type of result is also reported in the mixtures of CTAB and CPC [66] and also
in NaC−sodium dodecanoate in Tris hydrochloric acid buffer, with negative values of β (for
αCTAB<0.5 or αSDS< 0.5 respectively) [68] and positive β value at elevated mole fractions.
Hence these surfactants have similar head groups but different hydrophobic tails. The
antagonistic interactions in the binary mixtures of different amphiphiles differ either in size
of head group or hydrophobic moieties, that can be due to the geometric packing in supra
molecular aggregates of amphiphilic molecules [69, 70] and is reported in a few binary
mixers of cationic gemini surfactant and the zwitter ionic lipid 1,2-dioleoyl-syn-glycero-3-
phosphoethanolamine (DOPE).[71] In SDS and gemini surfactant mixed systems the values
of X1 (Table 1/ Table 2) indicates that [BSC14-C6-14CSB]/[BSC16-C6-16CSB] participates
in the mixed aggregate formation of gemini surfactants because of same hydrophobicity thus
enhances the incorporation to large extent in the mixed micelles. Hence the mixed micelles of
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SDS and [BSC14-C6-14CSB]/[BSC16-C6-16CSB] at higher mole fractions are more affluent
of SDS surfactant when related to their ideal values obtained from Clint model of ideal
mixing behaviour with X1<Xideal for the entire mole fractions. This type of results has been
reported in mixtures of cationic bis-dodecyldimethylammonium gemini cationic surfactants
of type 12-s-12 with changeable length of spacer and the NaTDC (bile salt sodium
taurodeoxycholate) [72]. The GE values are negative suggesting that the mixed micelle
formation was stable as relevant to those pure components. The value of GE decreases with
increase in micellar mole fraction revealing that mixed micelles formed are not stable due to
packing geometry constraints of hydrophilic head group induced by incompatibility of
hydrophobic core[73].
3.3 Thermodynamics of micellization
The micelle formation can be viewed as an association, dissociation process by which
surfactant molecules and micelles coexist as according to mass action model and show
separation and aggregation constantly to reach dynamic equilibrium finally[74]. The process
of micellization in gemini surfactant can be represented as given below
nG2  2nNa
M2n(1)
(7)
where G2-, Na+, and M2n(1-α)- corresponds to the anionic gemini surfactant, counter ion, and
the aggregation of monomer, respectively, n is the micellar aggregation number and α
represents the degree of counter ion binding. The Gibbs free energy of micellization per mole
of the gemini surfactant (ΔGmic) is given by
1



Gmic  RT  ln 
 ln G2  2nln Na 
(8)
2n(1 )



M
n
where R is ideal gas constant, T is the temperature in Kelvin, and 푎 is an activity of an ion.
As micelles are formed by means of huge number of monomeric units the n value is very
14

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large and the first term in the parentheses will be minute and could be neglected. Further, the
activities of the ions have the following correlation[75].
1
G2  Na   cmc
(9)
2
Ion activities can be replaced by xCMC i.e. cmc expressed in mole fraction of the surfactant in
the aqueous solution at very low concentration. The Gibbs free energy of micellization
(ΔGmic) to each gemini surfactant at a given temperature can be expressed as [74, 76, 77]
Gmic  (3 2)RT ln Xcmc
(10)
(11)
(12)
According to the following Gibbs-Helmholtz equation (11):
 G T 
Hmic
T 2


mic
ꢀ

P  




T



P
the enthalpy changes of micellization, ∆Hmic is evaluated from the subsequent equation:
 ln X
Hmic  (3  2)RT2


p


cmc T
The variation of lnxCMC with temperature has been empirically estimated by a second degree
polynomial and has been reported as[78].
ln Xcmc (T)  gT 2  hT  j
(13)
and
'
d  j'  h'T  g'T2
(14)
where g, h, j are polynomial constants and can be obtained from least squares regression
analysis by fitting lnxCMC as function of the respective temperature (T), after that the value of
∆Hmic is calculated. The entropy change (∆Smic) can be obtained from following expression:
Hmic  Gmic
Smic

(15)
T
15

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The value of cmc, α, ∆Gmic, ∆Hmic and ∆Smic for SDS, pure gemini surfactant [BSC14-C6-
14CSB]/[BSC16-C6-16CSB] are given in Table: S1. The process of micellization is
temperature dependent, thus different thermodynamic parameter has been evaluated from the
values of cmc. The plots of Gibbs free energy (∆Gmic), enthalpy change (∆Hmic), and entropy
change (∆Smic) of micellization against temperature are given in Figure: 2 respectively. The
values of ∆Gmic are negative at various temperatures for both the gemini surfactants
suggesting that the process of micellization is a spontaneous. However, the values of ΔGmic
become more negative with decrease in length of the linker group at a particular temperature.
It has been observed that the ∆Hmic values are negative at various temperatures, which
highlights that the micellization is an exothermic process. The ∆Hmic value enhances with the
rise of temperature. In ionic surfactant, the increase in temperature affects the ∆Hmic generally
by two reasons. (i) Increase in temperature can break the structure of water molecular
aggregation around the alkyl chain, which increases the value of ∆Hmic greatly. (ii) The
micelle is negatively associated by condensation of alkyl chains with increase in temperature
and induces ∆Hmic to decrease negatively[79]. Therefore, for each gemini surfactants [BSC14-
6-14CSB], [BSC16-6-16CSB], the values of ∆Hmic becomes less negative with the rise of
temperature. The values of ΔSmic are observed positive (except 0.7α in [BSC16-C6-16CSB]
and enhance with the rise in temperature, reveals that the icebergs formed by ordering of
water molecules surrounding the hydrophobic tails were destroyed by the micellization, and
the system gets further disordered. Further, the destruction of structure of iceberg is strong as
compared to haphazardly oriented gemini anions by a solvated form to the micelles. Thus
with increase of temperature reduces the number of the ordered water molecules and the
demolition of the iceberg structure relieves less water molecules free when the micellization
process was carried out at higher temperatures[80]. Thus, it is obvious that TΔSmic>ΔHmic
16

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indicating that the micellization of each gemini surfactant and its binary mixtures with SDS
in aqueous solution is an entropy-driven process.
3.4 Fluorescence Measurements.
3.4.1 CMC from fluorescence probe
Fluorescent probes are widely used to determine different micellar parameters like cmc
(Figure: 3a,3c), micro fluidity, aggregation number (Nagg), experimental dielectric constant
(De)[64]. In micellar medium it depends upon the chemical structure of fluorophore and
micellar solution properties. The pyrene solvent polarity is distinct by the I1/I3 intensity
emission ratio, where I1 represents S1 to So transition and I3 corresponds to S1 (v= 0) to S0 (v =
1) intensity transition in pyrene. The I1/I3 increases with increasing dipolarity of solvent and
acts as function of solvent dielectric and refractive index by a dielectric cross term
[f(ε,n2)][81]. The Figure: 3b, 3d shows I1/I3 vs. log concentration of gemini surfactant
[BSC14-C6-14CSB], [BSC16-C6-16CSB] respectively. A moderately drastic change in I1/I3
represents the onset of micelle formation known as cmc. This suggests that hydrophobic
pyrene gets incorporated in to the micellar pseudo phase upon micellar formation. The cmc
evaluated from pyrene fluorescence in presence of [BSC14-C6-14CSB], [BSC16-C6-16CSB]
respectively were 0.45 and 0.31× 10-6M and are in good conformity with the results obtained
from conductance measurements.
3.4.2 Aggregation number and Ksv
The aggregation number of gemini surfactants with different mole fractions of SDS was
obtained from quenching of pyrene probe by benzoquinone (BZQ). The fluorescence of the
different mole fractions using pyrene probe has been done. It is acknowledged that
the quantitative relation of initial and third vibronic peaks (I1/I3) of pyrene spectrum
(Figure: S6, Figure: S7) shows the polarity of the medium in which it is dissolved. The I1/I3
results for all the binary mixtures of the two gemini [BSC14-C6-14CSB]/[BSC16-C6-
17

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16CSB] with SDS over the complete mole fraction range were drained to calculate the
micro polarity. Every spectrum shows one to five vibronic peaks at totally
different wavelengths. The micellar aggregation numbers (Nagg) were measured by
steady state fluorescence measurements at totally different mole fractions. The surfactant
solution (30×10–6M) was added and pyrene concentration was kept constant (1 × 10-6M).
The quencher concentration was varied from zero to a 120 10-6M. It has been
observed that the presence of a quencher within the micelle is more as compared to life
time of fluorescence probe. The pyrene fluorescence quenching by BZQ was accustomed
to verifying the Nagg. The model planned by Turro and Yekta were utilized to determine
the fluorescence quenching and size of micelles. According to this model, the
probability Pn of an existing micelle that contain n quencher molecules[79].
X n
P 
exp(m)
(16)
n
n!
where m is the average number of quencher (Q) per molecule of micelle (M), m = [Q]/[M].
The fluorescence of the probe (pyrene) molecule occurs in absence of quencher in the micelle
(i.e. n = 0) and the probability gets equal to P0 = exp (–m). The intensity I of pyrene emission
is thus directly proportional to P0. If the gemini solution do not have any quencher, the
fluorescence probe intensity becomes equal to I0, and thus probability of fluorescence is equal
to 1. Therefore, following expression can be used for calculating aggregation number (Nagg).
I0
I
([GS]  cmc)
(Nagg [BZQ]
ln

(17)
where Gs is concentration of the mixture and BZQ is the quencher concentration of BZQ as a
quencher. The ratio of ln I0/I verses concentration of the quencher [BZQ] (Figure: S8, Figure:
S9) give a straight-line having slope equal to reciprocal of micellar concentration. Thus,
knowing the total concentration of mixture Gs and the concentration of surfactant non-
associated in micelles, this is nearly equal to the cmc, to calculate the aggregation number.
18

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The aggregation numbers were obtained from steady state measurements in pure and mixed
systems which are given in Table 2. The observed values of Nagg of the various mole fractions
of SDS-[BSC14-C6-14CSB] mixture i.e., 0.1, 0.3 and 0.7 is lower than that for pure gemini
surfactant, in such cases the presence of SDS as co-solvent in aqueous [BSC14-C6-14CSB] is
able to minimize the Nagg to higher extent and may be due to the more repulsive
interactions[82]. However, the overall trend is increasing suggesting that repulsive
interactions among the hydrophilic groups of anionic SDS molecules are dominant. While in
SDS-[BSC16-C6-16CSB] mixture Nagg values of pure gemini surfactant are lower than that of
entire mole fractions used. The increase of Nagg with increasing mole fraction is associated
with the increase in repulsive interactions between the hydrophilic groups of anionic SDS
molecules, which are gradually substituted by gemini surfactants. As a result, the usual
surface optimal area per head group of the surfactant increases. Smaller aggregation number
means higher charge of density. The size of mixed micelles in solution is determined by the
electrostatic repulsions among the hydrophilic groups because of steric hindrance caused by
hydrophobic tails. Thus, the above observed findings can be explained based on quenching
mechanism. The hydrophobic environment strength can be determined by evaluating the first
order quenching constant (KSV), using the relation:
I0
 1 KSV [BZQ]
(18)
I
where KSV is a product of lifetime of the probe and rate constant of quenching process in
absence of bimolecular quenching and shows a bimolecular quenching and unimolecular
decay[83]. Thus, higher the solubility of the quencher and the probe, greater would be the
KSV accordingly. The results observed can also be elaborated in terms of micro polarity
environment of mixed micelles of gemini surfactant. Usually a value less than 1 reveals that
the pyrene is present in non-polar environment where as value more than 1 indicates polar
microenvironment for pyrene[81]. The mean values of I1/I3 ratio at various mole fractions are
19

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given in Table 2. The values are very near to methanol (1.33) that shows resemblance
between the environment of the solubilized pyrene in the system and in methanol[81]. The
experimental dielectric constant (De) of the solution can be evaluated by using the following
relation:
I0
 1.00461 0.01253De
(19)
I
and the theoretical dielectric constant (Did) in the mixed micelles has been calculated from
the subsequent equation:
(20)
Did

D X
i i

where Di is the dielectric constant, Xi is the theoretical micellar value of ith mole fraction. The
data suggested that experimental values differ from the calculated ones suggesting that the
occurrence of attractive interactions among the surfactant in the mixed micelles.
Conclusion
Two novels anionic gemini surfactants i.e., [BSC14-C6-14CSB] and [BSC16-C6-16CSB]
were synthesised and characterised. The physicochemical properties of the SDS with
[BSC14-C6-14CSB] and [BSC16-C6-16CSB] were investigated by various methods. The
Clint model describing ideal mixing behaviour in all the studied binary mixtures and regular
solution theory were used to describe binary systems. The parameters like cmc٭, mole
fraction in ideal mixtures (Xideal), in real mixed micelles (X1) and interaction parameter (β)
were also determined. The synergistic interaction was observed in all the studied mole
fractions of SDS due to the attractive as well as repulsive interactions among the amphiphiles
in the mixed aggregates. The negative value of ∆Gmic in both pure components and for
mixtures indicates micelle formation is thermodynamically favourable as ∆Hmic is also
negative at lower temperature and then becomes positive at higher temperature. Higher
values of ∆Smic than ∆Hmic indicates that process of micellization is entropy driven. The value
20

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of Nagg, (determined by using pyrene probe fluorescence quenching method) increases with
increasing mole fraction. Further, with increasing mole fraction of SDS, KSV also increases.
This indicates the existence of attractive interactions among the surfactant in the mixed
micellar solutions.
Acknowledgements
Dr. Rajan Patel thanks to Science and Engineering Research Board (SERB), New Delhi for
providing research grant with Sanction Order No. (SB/EMEQ-097/2013 and
EEQ/2016/000339). Authors also thank DST for providing the FIST grant with Sanction
Order No. (SR/FIST/LS-541/2012).
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References
[1] H. Schott, Journal of Pharmaceutical Sciences 74 (1985) 1140.
[2] C. Tanford, The hydrophobic effect: formation of micelles and biological membranes 2d ed. J.
Wiley., 1980.
[3] L. Zhou, J. Yue, Y. Fan, Y. Wang, Langmuir. 34 (2018) 12924.
[4] R.H. Müller, Colloidal carriers for controlled drug delivery and targeting: Modification,
characterization and in vivo distribution. Taylor & Francis, 1991.
[5] S. Cohen, H. Bernstein, Microparticulate systems for the delivery of proteins and vaccines. CRC
Press, 1996.
[6] F. Khan, U.S. Siddiqui, M.A. Rub, I.A. Khan, Kabir-ud-Din, Journal of Dispersion Science and
Technology 36 (2015) 83.
[7] N. Azum, M.A. Rub, A.M. Asiri, Journal of Solution Chemistry 45 (2016) 791.
[8] O. Kaczerewska, B. Brycki, I. Ribosa, F. Comelles, M.T. Garcia, Journal of industrial and
engineering chemistry 59 (2018) 141.
[9] V.P. Torchilin, J. Control Release. 73 (2001) 137.
[10] R. Patel, M.U.H. Mir, J.K. Maurya, U.K. Singh, N. Maurya, M.u.d. Parray, A.B. Khan, A. Ali,
Luminescence. 30 (2015) 1233.
[11] F. Menger, C. Littau, J. Am. Chem. Soc. 115 (1993) 10083.
[12] F.M. Menger, J.S. Keiper, Angewandte Chemie International Edition 39 (2000) 1906.
[13] R. Zana, Advances in colloid and interface science 97 (2002) 205.
[14] I.A. Khan, R. Mohammad, M.S. Alam, J. Chem. Eng. Data 55 (2009) 370.
[15] M.S. Alam, V. Nareshkumar, N. Vijayakumar, K. Madhavan, A.B. Mandal, J. Mol. Liq. 194 (2014)
206.
[16] I.A. Khan, R. Mohammad, M.S. Alam, J. surfactants deterg. 13 (2010) 179.
[17] M.S. Alam, N. Kamely, A.M. Siddiq, K. Madhavan, N. Vijayakumar, V. Nareshkumar, A.B. Mandal,
Journal of Dispersion Science and Technology 36 (2015) 1029.
[18] M.S. Alam, A.B. Mandal, J. Mol. Liq. 212 (2015) 237.
[19] A.M. Siddiq, T. Parandhaman, A.F. Begam, S.K. Das, M.S. Alam, Enzyme and microbial
technology 95 (2016) 118.
[20] M.S. Alam, A.M. Siddiq, R. Ragupathy, A.B. Mandal, Journal of Dispersion Science and
Technology 38 (2017) 280.
[21] M.S. Alam, A.M. Siddiq, J. Mol. Liq. 242 (2017) 1075.
[22] M.S. Alam, A.M. Siddiq, D. Natarajan, M.S. Kiran, G. Baskar, J. Mol. Liq. 273 (2019) 16.
[23] R. Srivastava, M.S. Alam, International journal of biological macromolecules 122 (2019) 72.
[24] J. Singh, P. Yang, D. Michel, R. E Verrall, M. Foldvari, I. Badea, Curr. Drug. Deliv. 8 (2011) 299.
[25] S.D. Wettig, R.E. Verrall, M. Foldvari, Current gene therapy 8 (2008) 9.
[26] M. Maslov, N. Morosova, I. Senan, G. Serebrennikova, Russian journal of bioorganic chemistry
35 (2009) 628.
[27] Y.-S. Ding, M. Zha, J. Zhang, S.-S. Wang, Colloids and Surfaces A: Physicochemical and
Engineering Aspects 298 (2007) 201.
[28] Q.Q. Baltazar, J. Chandawalla, K. Sawyer, J.L. Anderson, Colloids and Surfaces A:
Physicochemical and Engineering Aspects 302 (2007) 150.
[29] M. Ao, P. Huang, G. Xu, X. Yang, Y. Wang, Colloid and Polymer Science 287 (2009) 395.
[30] A. Bhadani, S. Singh, Langmuir. 25 (2009) 11703.
[31] E. Fisicaro, C. Compari, M. Biemmi, E. Duce, M. Peroni, N. Barbero, G. Viscardi, P. Quagliotto, J.
Phys. Chem. B. 112 (2008) 12312.
[32] C. Akbay, Y. Hoyos, E. Hooper, H. Arslan, S.A. Rizvi, Journal of Chromatography A 1217 (2010)
5279.
[33] F. Menger, J. Keiper, V. Azov, Langmuir. 16 (2000) 2062.
[34] L. Pérez, A. Pinazo, M.J. Rosen, M.R. Infante, Langmuir. 14 (1998) 2307.
22

ACCEPTED MANUSCRIPT
[35] Y.-S. Ge, S.-X. Tai, Z.-Q. Xu, L. Lai, F.-F. Tian, D.-W. Li, F.-L. Jiang, Y. Liu, Z.-N. Gao, Langmuir. 28
(2012) 5913.
[36] C.M. Faustino, A.R. Calado, L. Garcia-Rio, Biomacromolecules 10 (2009) 2508.
[37] C.M. Faustino, A.R. Calado, L. Garcia-Rio, J. Colloid Interface Sci. 359 (2011) 493.
[38] C.M. Faustino, A.R. Calado, L. Garcia-Rio, J. Colloid Interface Sci. 367 (2012) 286.
[39] I.A. Bhat, B. Roy, Journal of industrial and engineering chemistry 63 (2018) 348.
[40] L.K. Tiwary, A. Mandal, M.S. Alam, S. Thennarasu, A.B. Mandal, Colloids and Surfaces B:
Biointerfaces 82 (2011) 126.
[41] M.S. Alam, A.B. Mandal, J. Mol. Liq. 168 (2012) 75.
[42] M.S. Alam, R. Ragupathy, A.B. Mandal, Journal of Dispersion Science and Technology 37 (2016)
1645.
[43] M.S. Alam, A.M. Siddiq, A.B. Mandal, Journal of Dispersion Science and Technology 38 (2017)
303.
[44] M.S. Alam, B. Ashokkumar, A.M. Siddiq, J. Mol. Liq. 251 (2018) 458.
[45] M.S. Alam, A.M. Siddiq, J. Mol. Liq. 252 (2018) 321.
[46] K. Tsubone, J. Colloid Interface Sci. 261 (2003) 524.
[47] C.l.M. Faustino, C.u.S. Serafim, I.s.N. Ferreira, M.A. Branco, A.n.R. Calado, L. Garcia-Rio,
Industrial & Engineering Chemistry Research 53 (2014) 10112.
[48] M. Kamil, H. Siddiqui, Modeling and Numerical Simulation of Material Science 3 (2013) 17.
[49] Z. Miskolczy, K. Sebők-Nagy, L. Biczók, S. Göktürk, Chemical physics letters 400 (2004) 296.
[50] Z.H. Asadov, S.M. Nasibova, R.A. Rahimov, G.A. Ahmadova, S.M. Huseynova, J. Mol. Liq. 225
(2017) 451.
[51] M.J. Rosen, Surfactants and Interfacial Phenomena, Third Edition (2004) 303.
[52] R. Williams, J. Phillips, K. Mysels, Transactions of the Faraday Society 51 (1955) 728.
[53] J. Phillips, Transactions of the Faraday Society 51 (1955) 561.
[54] A.B. Khan, F.A. Wani, N. Dohare, M.u.d. Parray, P. Singh, R. Patel, J. Chem. Eng. Data 62 (2017)
3064.
[55] R. Kamboj, S. Singh, V. Chauhan, Colloids and Surfaces A: Physicochemical and Engineering
Aspects 441 (2014) 233.
[56] P. Carpena, J. Aguiar, P. Bernaola-Galván, C. Carnero Ruiz, Langmuir. 18 (2002) 6054.
[57] R. Patel, A.B. Khan, N. Dohare, M.M. Ali, H.K. Rajor, J. surfactants deterg. 18 (2015) 719.
[58] J.H. Clint, Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in
Condensed Phases 71 (1975) 1327.
[59] D. Rubingh, Plenum Press: New York, 1979.
[60] P. Holland, D. Rubingh, The Journal of Physical Chemistry 87 (1983) 1984.
[61] A. Ali, U. Farooq, S. Uzair, R. Patel, J. Mol. Liq. 223 (2016) 589.
[62] H. Asano, M. Ueno, Structure-Performance Relationships in Surfactants, CRC Press, 2003, p.
237-294.
[63] B.W. Ninham, V. Yaminsky, Langmuir. 13 (1997) 2097.
[64] Y. Moroi, Micelles: theoretical and applied aspects. Springer Science & Business Media, 1992.
[65] B. Kronberg, Curr. Opin. Colloid Interface Sci. 2 (1997) 456.
[66] M.E. Haque, A.R. Das, A.K. Rakshit, S.P. Moulik, Langmuir. 12 (1996) 4084.
[67] Y. Yunomiya, T. Kunitake, T. Tanaka, G. Sugihara, T. Nakashima, J. Colloid Interface Sci. 208
(1998) 1.
[68] R. Eising, S. Morés, I.C. Bellettini, A.C. Felippe, A.G. Dal-Bó, D. Zanette, Química Nova 31 (2008)
2065.
[69] C. Manohar, J. Narayanan, Colloids and Surfaces A: Physicochemical and Engineering Aspects
403 (2012) 129.
[70] J.N. Israelachvili, D.J. Mitchell, B.W. Ninham, Journal of the Chemical Society, Faraday
Transactions 2: Molecular and Chemical Physics 72 (1976) 1525.
[71] J. Akbar, N. Tavakoli, D.G. Marangoni, S.D. Wettig, J. Colloid Interface Sci. 377 (2012) 237.
23

ACCEPTED MANUSCRIPT
[72] Y. Wang, E.F. Marques, J. Mol. Liq. 142 (2008) 136.
[73] A.B. Khan, N. Dohare, R. Patel, World Academy of Science, Engineering and Technology,
International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering 9
(2015) 490.
[74] R. Mousli, A. Tazerouti, J. surfactants deterg. 14 (2011) 65.
[75] S. Zhang, J. Yu, J. Wu, W. Tong, Q. Lei, W. Fang, J. Chem. Eng. Data 59 (2014) 2891.
[76] S.M. Shaban, I. Aiad, M.M. El-Sukkary, E. Soliman, M.Y. El-Awady, Journal of Industrial and
Engineering Chemistry 20 (2014) 4194.
[77] J. Frahm, S. Diekmann, A. Haase, Berichte der Bunsengesellschaft für physikalische Chemie 84
(1980) 566.
[78] P. Patial, A. Shaheen, I. Ahmad, Journal of Industrial and Engineering Chemistry 20 (2014) 4267.
[79] U. Farooq, R. Patel, A. Ali, Journal of Solution Chemistry (2018) 1.
[80] Z.H. Asadov, R.A. Rahimov, K.A. Mammadova, A.V. Gurbanov, G.A. Ahmadova, J. surfactants
deterg. 19 (2016) 145.
[81] K. Kalyanasundaram, J. Thomas, J. Am. Chem. Soc. 99 (1977) 2039.
[82] K. Behera, H. Om, S. Pandey, J. Phys. Chem. B. 113 (2008) 786.
[83] V. Pimienta, G. Lévy, D. Lavabre, J. Laplante, J. Micheau, Physica A: Statistical Mechanics and its
Applications 188 (1992) 99.
Figure captions:
Figure 1. Plots of specific conductance vs. concentration of (a) BSC14-C6-14CSB, (b)
BSC16-C6-16CSB, and (c) SDS.
Figure 2. Plots of Gibbs free energy, ΔGmic, (a), enthalpy, ΔHmic, (b), and entropy, ΔSmic, (c)
of micellization vs. T (K).
Figure 3. Fluorescence emission spectra and their cmc plots of I1/I3 vs. conc. of [BSC14-C6-
14CSB] and [BSC16-C6-16CSB].
24

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Figure 1. Plots of specific conductance vs. concentration of (a) BSC14-C6-14CSB, (b)
BSC16-C6-16CSB, and (c) SDS.
25

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26

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Figure 2. Plots of Gibbs free energy, ΔGmic, (a), enthalpy, ΔHmic, (b), and entropy, ΔSmic, (c)
of micellization vs. T (K).
Figure 3. Fluorescence emission spectra and their cmc plots of I1/I3 vs. conc. of [BSC14-C6-
14CSB] and [BSC16-C6-16CSB].
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Table: 1 Micellar parameter like values of (cmc), ideal (cmc*), micellar composition (X1,
Xideal), interaction parameter (β), activity coefficients (f1, f2) and excess free energy of mixing
(GE) for SDS + [BS14-C6-14CSB] and SDS + [BS16-C6-16CSB].
cmca
X1
X ideal
β
f1
f2
GE
cmc٭
Mole
fraction
-4
(10-4mM) (10-4 mM)
(
10
)
a
(αSDS
)
SDS+ [BSC14-C6-14CSB]
298.15 K
0.1
4.40
5.70
7.80
14.7
36.9
6.10
7.80
10.9
18.3
54.9
0.126 0.118 -12.56 0.06 0.81
0.131 0.457 -10.96 0.25 0.82
0.140 1.067 -10.17 0.54 0.81
0.115 2.491 -08.11 1.73 0.89
0.165 9.602 -07.95 3.90 0.80
-2.80
-5.70
-6.30
-4.22
-1.77
0.3
0.5
0.7
0.9
303.15 K
0.1
5.60
7.30
7.90
13.7
41.0
6.77
8.71
12.1
20.3
60.9
0.094 0.128 -11.07 0.11 0.90
0.096 0.496 -09.49 0.42 0.91
0.158 0.157 -10.79 0.47 0.76
0.125 02.70 -08.53 1.45 0.87
0.169 10.40 -07.94 4.14 0.79
-2.46
-4.94
-6.68
-4.44
-1.77
0.3
0.5
0.7
0.9
308.15 K
0.1
8.0
8.11
10.4
14.5
24.3
79.9
0.012 0.148 -06.93 1.16 0.99
0.089 0.496 -09.04 0.55 0.93
0.150 1.339 -10.25 0.60 0.79
0.151 3.124 -09.07 1.44 0.81
0.169 12.04 -05.90 9.24 0.93
-1.54
-4.70
-6.35
-4.72
-1.31
0.3
8.90
9.90
17.0
61.0
0.5
0.7
0.9
313.15 K
0.1
5.90
6.70
7.80
14.9
45.1
6.77
8.71
12.1
20.3
60.9
0.076 0.119 -10.41 0.13 0.94
0.118 0.461 -10.42 0.30 0.86
0.161 01.07 -11.02 0.42 0.75
0.147 02.50 -09.25 1.19 0.81
0.139 09.67 -07.08 5.23 0.87
-2.32
-5.42
-6.83
-4.81
-1.58
0.3
0.5
0.7
0.9
28

ACCEPTED MANUSCRIPT
318.15 K
0.1
4.80
5.50
7.50
11.6
43.4
4.88
6.28
8.79
14.6
43.9
0.016 0.079 -07.98 0.47 0.99
0.078 0.305 -09.38 0.34 0.94
0.089 0.711 -08.78 0.68 0.93
0.115 01.66 -08.64 1.14 0.89
0.013 06.40 -03.11 4.81 0.99
-1.76
-4.88
-5.44
-4.50
-0.69
0.3
0.5
0.7
0.9
aUncertainties in αSDS = ± 0.01 and cmc = ± 0.1 (10-3mM).
Table: 2 Micellar parameters like values of (cmc), ideal (cmc*), micellar composition (X1,
Xideal), interaction parameter (β), activity coefficients (f1, f2) and excess free energy of mixing
(GE) for SDS + [BS16-C6-16CSB].
cmca
X1 X ideal
β
f1
f2
GE
cmc٭
Mole
fraction
-4
(10-4mM) (10-4 mM)
(
10
)
a
(αSDS
)
SDS+ [BSC16-C6-16CSB]
298.15 K
0.1
3.80
4.80
6.70
11.0
33.9
3.88
4.99
6.99
11.6
34.9
0.019 0.075 -8.22 3.71 0.996 -1.83
0.032 0.291 -7.54 8.60 0.992 -3.92
0.035 0.679 -6.75 18.5 0.991 -4.18
0.045 01.58 -6.25 33.2 0.987 -3.25
0.028 06.11 -4.09 208 0.996 -0.91
0.3
0.5
0.7
0.9
303.15 K
0.1
4.70
6.0
4.77
6.14
8.59
14.3
42.9
0.014 0.090 -7.63 6.07 0.998 -1.70
0.020 0.349 -6.67 16.5 0.997 -3.47
0.3
0.5
8.30
13.8
41.9
0.029 0.815 -6.3
0.031 01.90 -5.5
26.4 0.994 -3.9
57.6 0.994 -2.86
0.7
0.9
0.028 07.33 -3.66 303 0.997 -0.81
308.15 K
0.1
5.0
5.11
0.019 0.093 -7.93 4.83 0.997 -1.77
29