Aggregation and thermodynamic properties of some cationic gemini surfactants

Article abstract of DOI:10.1007/s11743-011-1270-7

In this study, the gemini surfactants of the alkanediyl-α-ω- bis(alkyl dimethyl ammonium) dibromide type, on the one hand, with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred to as ''m-2-m'' (m = 10, 12 and 16) and, on

Full text of DOI:10.1007/s11743-011-1270-7

J Surfact Deterg (2012) 15:33–40
DOI 10.1007/s11743-011-1270-7
ORIGINAL ARTICLE
Aggregation and Thermodynamic Properties of Some Cationic
Gemini Surfactants
•
Halide Akbas¸ Aylin Elemenli Mesut Boz
•
Received: 24 November 2010 / Accepted: 29 March 2011 / Published online: 20 April 2011
Ó AOCS 2011
Abstract In this study, the gemini surfactants of the al-
kanediyl-a-x-bis(alkyl dimethyl ammonium) dibromide
type, on the one hand, with different alkyl groups contain-
ing m carbon atoms and an ethanediyl spacer, referred to as
‘‘m-2-m’’ (m = 10, 12 and 16) and, on the other hand, with
n-C16 alkyl groups and different spacers containing s carbon
atoms, referred to as ‘‘16-s-16’’ (s = 2, 6, 10 and Ar (8))
have been synthesized, purified and characterized. The
critical micelle concentration (CMC), micelle ionization
Keywords Cationic gemini surfactants ꢀ Spacer group ꢀ
Critical micelle concentration ꢀ Micelle ionization degree
Introduction
Surfactants are widely used in our daily life and in various
industrial productions. For instance, they catalyze some
reactions, act as solubilizers for water insoluble dyes, break
down dye aggregates in order to accelerate adsorption
processes on fibers, are auxiliaries for improving dye
adsorption and are used as leveling agents [1–4]. Gemini or
dimeric surfactants are rather novel surfactants that have
become of considerable interest in the academic and
industrial areas. Due to their different molecular structure
with respect to monomeric surfactants, they have superior
properties for special purposes [5–7]. Gemini surfactants
show bioactivity as disinfectants and are used in skin care
formulations, antipollution protocols, analytical separa-
tions, nanoscale technology and as paint additives.
degree (a) and Gibbs free energy of micellization (DGmic
)
of these surfactants and the monomeric cationic surfactants
DTAB and CTAB have been determined by means of
electric conductivity measurements. In addition, the tem-
perature dependence of the CMC was determined for the
10-2-10 gemini surfactant. The CMCs of the gemini sur-
factants are found to be much lower than those of the cor-
responding monomeric surfactants and the effect of the
hydrophobic alkyl chain length is more important than that
of the spacer. The CMC of 16-s-16 passes through a max-
imum of (or around) s = 6 and then decreases for s = 10.
The presence of a maximum CMC is explained by the
contribution of a change of conformation of the surfactant
with increasing spacer chain length. The changes of a with s
and m are found qualitatively similar to those found for
CMC values. The values of DGmic are more negative for the
dimers than for the monomers and also change with an
increasing spacer carbon number, as CMC values do. The
thermodynamic parameters of micellization indicate that
the micellization of 10-2-10 is enthalpy driven.
Gemini surfactants consist of two amphiphilic moieties
connected at the level of or very close to the head groups
by a ‘‘spacer’’ group of varying nature namely hydropho-
bic, hydrophilic, rigid or flexible [8, 9]. As the spacer and
alkyl groups play an important role in the properties of
gemini surfactants [10–12], we focused on the effect
of those moieties on the aggregation properties of some
cationic gemini surfactants. For this purpose, a series of
quaternary ammonium dimeric surfactants (Cm–s–Cm, 2Br,
s = 2, m = 10, 12 and 16; m = 16, s = 2, 6, and 10) were
synthesized in our laboratory. The characteristic parame-
ters of these compounds and those of monomeric cationic
surfactants (DTAB and CTAB), such as critical micelle
concentration (CMC), micelle ionization degree (a) and
Gibbs free energy of micellization (DGmic) were determined
H. Akbas¸ (&) ꢀ A. Elemenli ꢀ M. Boz
Department of Chemistry, Faculty of Sciences,
Trakya University, Edirne 22030, Turkey
e-mail: hakbas34@yahoo.com.tr
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J Surfact Deterg (2012) 15:33–40
by means of electric conductivity measurements. In addi-
tion, a surfactant with m = 16 containing a p-xylylene
spacer (–CH2–C6H4–CH2–), represented as 16-Ar (8)-16,
was also examined. We compared the aggregation behavior
and micellar properties of all these surfactants to study how
their aggregation in aqueous solution is affected by both
hydrophobic and spacer chain lengths of the surfactants.
It is widely recognized that the CMC is the most
important parameter in studies dealing with the micelli-
zation of surfactants. Because the CMC value of a sur-
factant can be considered as a measure of the stability of
the micellar form with regard to its monomeric form.
Another important aspect is related to the thermodynamic
studies of micellization. To obtain thermodynamic infor-
mation on the micellization process, the CMC values of
surfactants over a temperature range are used. The CMC
values are usually determined from the abrupt change of a
certain physical property over a very small concentration
range.
Fluka), 1-bromohexadecane (97%, Fluka), N,N,N0,N0-tet-
ramethyl ethylene ediamine (98%, Fluka), 1,6-dibromo-
hexane, (97%, Fluka), 1,10-dibromodecane, (95%, Fluka),
N,N-dimethylhexadecylamine (98%, Fluka), were used
without further purification. All solutions were prepared
with double distilled water in an all-glass apparatus. The
specific conductivity of this water was in the range of
(1–2) 9 10-6 S cm-1
.
Synthesis Schemes
The cationic gemini surfactants were synthesized by using
two different methods described by Zana et al. [12]
(Schemes 1, 2). The preferred solvent for both methods
was dry acetone [13]. The yields of the reaction were
almost quantitative 90–97%. Surfactant purity was checked
by nuclear magnetic resonance (NMR) and surface tension,
1
all with excellent results. H-NMR spectra were recorded
in CDCl3 solution with a Varian Mercury Plus 300 MHz
spectrometer. 13C-NMR spectra were recorded at 75 MHz.
Experimental
Conductance Measurements
Materials
The conductance as a function of surfactant concentration
was measured using a conductometer WTW Terminal 740
with a cell constant of 0.433 cm-1. The conductometer was
initially calibrated with standard KCl solutions in the
appropriate concentration range. The experiments were
performed at constant temperature by circulating water
through a jacketed cell holding the solution under study.
The experimental error in the temperature was minimized
to 0.1 °C.
The monomeric cationic surfactants, dodecyl trimethyl
ammonium bromide (DTAB, 98%) and hexadecyl tri-
methyl ammonium bromide (CTAB, 97%) were supplied
by Merck and used without further purification. The ori-
ginal materials for the syntheses of the cationic geminis,
alkanediyl-a-x-bis(alkyldimethylammonium) bromides:
1-bromodecane (97%, Fluka), 1-bromododecane (95%,
Scheme 1 Synthesis procedure
for gemini cationic surfactants
types 10-2-10, 12-2-12 and
16-2-16
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J Surfact Deterg (2012) 15:33–40
35
Scheme 2 Synthesis procedure
for gemini cationic surfactants
types 16-6-16, 16-10-16 and
16-Ar-16
2500
2000
1500
1000
500
increases insignificantly with temperature. The temperature
effect on surfactants CMC in aqueous solution is usually a
consequence of two opposite phenomena [14, 15]. First, as
temperature increases, the degree of hydration of the
hydrophilic groups decreases. This favors the aggregation
process and micellization can occur at lower concentration.
Second, with increasing temperature the breakdown of the
structured water surrounding the hydrophobic group can
occur. This does not favor micellization, as the low entropy
of structured water is the key driving force of the self-
association process. In addition, thermal motion also delays
micellization [15, 16]. Here it seems that the second effect
slightly predominates over the first in the narrow temper-
ature range studied.
323.15 K
318.15 K
313.15 K
308.15 K
303.15 K
298.15 K
293.15 K
The conductivity values for other surfactant solutions
were measured only at 303.15 K and the CMC values are
given in Table 2. These values are in good agreement with
reported values from the literature for 12-2-12, 16-2-16,
16-6-16, DTAB and CTAB. It can be seen from Table 2
that the micellization behavior of gemini surfactants is
significantly different from that of conventional ones.
Gemini surfactants have low CMC values compared with
corresponding conventional surfactants of equivalent chain
length. The CMC of 12-2-12 is about 15 times less than
that of DTAB and that of 16-2-16 about 23 times less than
that of CTAB (Figs. 2, 3). Doubling surfactant molecular
weight decreases CMC values. This indicates that the
studied dimeric species have a much better micelle-form-
ing ability than single tail-single head ones, probably
because the two hydrophobic chains of gemini surfactants
break the water structure earlier and thus increase the
tendency to form micelles.
0
0
4
8
12
16
20
24
10-2-10 concentration (mM)
Fig. 1 Conductivity plots of (10-2-10) in pure water at different
temperatures
Results and Discussion
Critical Micelle Concentration Determination
The CMC values of surfactant solutions were determined at
sharp break points on specific conductivity versus con-
centration curves. Figure 1 depicts representative conduc-
tivity plots of 10-2-10 in pure water at seven temperatures
ranging from 293.15 to 323.15 K. The increase of con-
ductivity with concentration, which is observed for dilute
solutions, is a direct result of the increasing number of free
ions. The CMC values taken from Fig. 1 are given in
Table 1. This table shows that the CMC of 10-2-10
The comparison of the results for the 10-2-10, 12-2-12
and 16-2-16 gemini surfactants shows that, as usually
observed, CMC values decrease for longer alkyl chains
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J Surfact Deterg (2012) 15:33–40
Table 1 Various micellization and thermodynamic parameters of (10-2-10) surfactant solutions at different temperatures
Temperature (K)
CMC (mmol/L)
293.15
6.62
298.15
6.63
303.15
6.65
308.15
6.67
313.15
6.69
318.15
6.70
323.15
6.71
Micelle ionization degree (a)
ꢁDG0mic (kJ/mol)
ꢁDG0m;tail
0.18
0.20
0.22
0.26
0.31
0.34
0.39
58.1
58.2
58.3
57.4
55.9
55.4
53.8
29.1
29.1
29.1
28.7
28.0
27.7
26.9
ꢁDHm0 ic (kJ/mol)
TDS0mic (kJ/mol)
46.6
11.6
48.1
10.1
49.7
8.5
51.3
6.0
53.0
3.0
54.6
0.7
56.3
-2.5
Table 2 Various micellization and thermodynamic parameters of m-s-m (s = 2, m = 10, 12 and 16 and m = 16, s = 2, 6, 10 and Ar(8))
surfactant solutions at 303.15 K
DG0m;tail (kJ/mol)
Surfactant
CMC (M)
Micelle ionization
degree (a)
Gibbs free energy of
micellization DG0mic (kJ/mol)
10-2-10
12-2-12
6.65 9 10-3
9.6 9 10-4
9.3 9 10-4a
8.4 9 10-4b
3.3 9 10-5
3.6 9 10-5c
4.6 9 10-5
4.3 9 10-5b
4.6 9 10-5d
4.1 9 10-5
6.1 9 10-5
1.5 9 10-2
1.6 9 10-2a
1.6 9 10-2e
9.5 9 10-4
9.1 9 10-4e
0.22
0.19
0.19a
0.22b
0.18
0.33c
0.39
0.48b
–
-58.3
-71.4
-29.1
-35.7
16-2-16
16-6-16
-95.4
-55.9
-47.7
-27.9
16-10-16
16-Ar(8)-16
DTAB
0.37
0.47
0.31
0.29a
0.28e
0.32
0.29e
-80.4
-71.2
-35.0
-40.2
-35.6
-35.0
CTAB
-46.5
-46.5
a
Wang Y, Marques EF (2008) Non-ideal behavior of mixed micelles of cationic gemini surfactants with varying spacer length and anionic
surfactants: A conductimetric study. J Mol Liquids 142:136–142
b
From Ref. [12] at 298.15 K
c
Junior PBS, Tiera VAO, Tiera MJ (2007) A fluorescence probe study of gemini surfactants in aqueous solution: a comparison between n-2-n
and n-6-n series of the alkanediyl-a,w-bis (dimethyl alkyl ammonium bromides). Ecletica Quimica 32:47–54
d
Khan IA, Khanam AJ, Khan ZA, Kabir-ud-Din (2010) Mixing behavior of anionic hydrotropes with cationic gemini surfactants. J Chem Eng
Data 55:4775–4779
e
Mata J, Varade D, Bahadur P (2005) Aggregation behavior of quaternary salt based cationic surfactants. Thermochimica Acta 428:147–155
(Table 2). These CMC values are quite different from each
other. The stability of the m-2-m surfactant monolayer
increases with the hydrophobic chain length, in direct
relation to stronger hydrophobic interaction [17]. Due to
their short spacer (–CH2–CH2–), the m-2-m double-headed
dicationic surfactants bear a high charge density on their
polar head (two ammonium cations close to each other).
So, the proximity of alkyl chains in 12-2-12 greatly
strengthens hydrophobic interaction, which results in small
CMC [18]. As seen in Table 2 and Fig. 4, with increasing
spacer length, the hydrophobic interaction is decreased and
thus the CMC increases (here for 16-6-16 compared with
16-2-16), however remaining lower than that of CTAB.
The maximum of CMC indicates a minimum stability of
the surfactant in the micellar state. When the spacer is long
enough (s = 10), it tends to bend towards the micellar core
so as to reduce the Gibbs energy. By this way, the CMC
decreases again. Therefore, the CMC of gemini surfactants
is a non-monotonous function of the spacer length, with a
maximum value around 6 methylene groups [12]. For 16-2-
16 with short inter-charge spacer, the CMC values are only
slightly lower than those of 16-6-16 and 16-10-16. As seen
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J Surfact Deterg (2012) 15:33–40
37
2500
25
20
15
10
5
16-2-16
16-6-16
16-10-16
16-Ar(8)-16
DTAB
12-2-12
2000
1500
1000
500
0
0
0
4
8
12
16
0
5
10
15
20
25
Surfactant concentration (10-5 M)
Surfactant concentration (mM)
Fig. 2 Variation of the specific conductivity with concentration of
12-2-12 and DTAB solutions at 303.15 K
Fig. 4 Variation of the specific conductivity with the surfactant
concentration for (16-s-16), s = 2, 4, 10 and Ar (8) solutions at
303.15 K
160
as 6.1 9 10-5 M, which is about 16 times smaller than that
of CTAB. In fact, as expected, an aryl spacer is less
hydrophobic than the corresponding alkyl one. Alterna-
tively, it may be an indication of the packing arrangement
of the corresponding surfactant at the air–water interface.
That is to say, the interaction between surfactant monomers
and the length and flexibility of spacer chain are the main
factors that account for the behavior of the spacer [19, 20].
Similar observations have been made recently by
researchers, who have examined both acetylenic spacers
and the p-xylylene spacer [10, 13].
120
CTAB
80
16-2-16
40
0
Micelle Ionization Degree (a)
In order to explain the aggregation behavior of gemini
surfactants in aqueous solutions, the electric conductivity
of these solutions was measured. As seen in Fig. 1, a
temperature rise results in a conductivity increase, espe-
cially above the CMC. The pre-micellar slope (S1 = dj/
dCC[CMC) is always higher than the post-micellar one
(S2 = dj/dCC\CMC) and their ratio can be used for a rough
evaluation of the micelle ionization degree (a = S2/S1)
[12, 21, 22].
0
40
80
120
160
200
Surfactant concentration (10- 5 M)
Fig. 3 Variation of the specific conductivity with the surfactant
concentration for 16-2-16 and CTAB solutions at 303.15 K
as Table 2, CMC values depend significantly on the alkyl
chain length and at a less important degree on the spacer
chain length. Similar results have been found by Zana et al.
[12] for a series of 12-s-12 (s = 2–16) at 25 °C.
If one considers that a benzene ring can be approxi-
mated as being equivalent to 3–3.5 methylene units in
length, then the Ar(8) spacer is equivalent to 5–5.5 meth-
ylene units. The CMC of 16-Ar (8)-16 surfactant is found
The micelle ionization degree describes the number of
counterions not bound to the micelle. The values of a for
10-2-10 at different temperatures are also given in Table 1.
It can be seen that a increases from 0.18 to 0.39 as tem-
perature rises from 293.15 to 323.15 K, Thus the degree of
counterion binding to micelles b (b = 1 - a) shows a
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J Surfact Deterg (2012) 15:33–40
trend to decrease with increase in temperature, suggesting
that the binding of counterions to micellar surface is an
exothermic process. Counterion binding is caused by an
electrostatic interaction between opposite charges [23]. a
values calculated for the dimeric and monomeric surfactant
at constant temperature are listed in Table 2. They decrease
gradually with increasing hydrophobic chain length.
According to the a values, we can obtain the b values as
0.72, 0.81 and 0.82 for 10-2-10, 12-2-12 and 16-2-16,
respectively, at 303.15 K. All these values are larger than
those corresponding to DTAB and CTAB (0.69 and 0.68,
respectively). This suggests that, in (m-2-m) type surfac-
tants, the binding ability of the Br- counterion is stronger
than in monomeric surfactants. The spacer may be
responsible for this result. In (m-2-m) type surfactants, the
hydrophilic head groups are closer to each other, resulting
in a higher effective positive charge density on the micelle
surface, thus increasing the attraction of counterions.
As mentioned before, with increasing spacer length,
hydrophobic interaction is reduced: that is why CMC and
micelle ionization degree increase: a is 0.18 for 16-2-16 and
0.39 for 16-6-16 (Table 2). Due to the above mentioned
reason, when the spacer is long enough (s = 10), a decreases
to a value (0.37) closer to that of CTAB (0.29–0.32).
When the spacer is short enough, the free energy of
micellization per chain of dimeric surfactant is the same as
that for monomeric surfactants. This behavior reflects the
fact that a short polymethylene spacer lies at the micelle/
water interface [24], and does not contribute to the free
energy of transfer. A different behavior is expected for a
long spacer which folds into the micelle hydrophobic core.
On the other hand, the standard enthalpy change for the
micellization of 10-2-10, DH0mic can be calculated by
applying the Gibbs–Helmholtz equation to Eq. 2
ꢂ
ꢀ
ꢁ
ꢀ
ꢁ ꢃ
o ln Xcmc
oT
oa
oT
DH0mic ¼ ꢁRT2 ð3 ꢁ 2aÞ
ꢁ ln Xcmc
P
Pð3Þ
The values of ln XCMC were plotted against temperature,
T. As seen in Fig. 5 a linear plot is obtained, whose slope is
d ln XCMC/dT,
The standard entropy values of micelle formation,
DS0mic, were evaluated from the calculated DH0mic and
DG0mic values as follows:
DH0mic ꢁ DG0mic
DS0mic/
¼
ð4Þ
T
The values of DG0mic, DG0mic;tail, DHm0 , and TDSm0 ic
,
obtained by using above equations for 10-2-10 are listed in
Table 1 and also the values of DG0mic, DGm0 ic;tail for all
Thermodynamics of Micellization
surfactants studied here are listed Table 2. The DHm0 ic
values are always negative, indicating that the micelle
formation process is exothermic. Nusselder and Engberts
[25] suggested that for the negative DH0mic, dispersion
forces play a major role in micelle formation. The
The temperature dependent values of CMC and a can be
used to obtain information about the thermodynamics of
micellization. The standard Gibbs free energies of micel-
lization for ionic surfactants (DG0mic) were calculated from
the relation derived for the charged phase separation model
of micellization [22]:
-9.010
-9.015
-9.020
-9.025
-9.030
-9.035
-9.040
-9.045
DG0micðmonomerÞ ¼ ð2 ꢁ aÞ RT ln XCMC
DG0micðdimerÞ ¼ ð3 ꢁ 2aÞRT ln XCMC
where XCMC is the value of CMC expressed in mole frac-
tion units (XCMC = CMC/(CMC ? number of moles of
pure water)). The Gibbs energy of micellization per alkyl
tail of dimeric surfactants (DG0mic;tail), was obtained
ð1Þ
ð2Þ
according to DG0mic;tail = DGm0 ic/2. Table 2 summarizes
both Gibbs energy values obtained by using Eqs. 1 and 2
for surfactants studied. As can be seen, Gibbs energy val-
ues were found to be negative in all the cases. At a constant
temperature (303.15 K), DG0mic decreases as the hydro-
phobic chain length increases, indicating that micellization
is more spontaneous and that its driving force gets stronger
due to hydrophobic interactions. It can be seen from
Table 2 that the free energy value for 16-6-16 is much
smaller than the others studied here. A very large decrease
of—DG0mic is observed in going from 16-2-16 to 16-6-16;
-9.050
290.00 295.00 300.00 305.00 310.00 315.00 320.00 325.00
Temperature (K)
Fig. 5 Plots of ln XCMC versus temperature for 10-2-10 in water
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J Surfact Deterg (2012) 15:33–40
39
DH0mic values do not vary significantly with temperature,
indicating no significant variation in the environment
surrounding the hydrophobic chain of the surfactant
molecule with increasing temperature.
surfactants is exothermic at all the temperatures studied.
Micelle formation process for the 10-2-10 gemini surfac-
tant is enthalpy-driven.
The DH0mic values for the gemini surfactants studied are
more negative than those of the corresponding monomeric
surfactants. These trends are similar to those found for
the hydrophobic gemini surfactant 12-2-12 and the corre-
sponding monomeric surfactant DTAB [12, 26]. In our
previous study, we investigated the thermodynamic para-
meters of hexadecyltrimethylammonium bromide (CTAB)
and dodecylpyridinium chloride (DPC) micellization in pure
water and different cosolvents at different temperatures [27,
28]. The smallest enthalpy values were -13.1 kJ mol-1 for
CTAB and -29.7 kJ mol-1 for DPC at 303.15 K. This dif-
ference in CMC and DH0mic between gemini and the corre-
sponding monomeric surfactants mostly arise from the
number of hydrophobic chains transferred from the aqueous
phase to the micelle core.
References
1. Sulthana SB, Rao PVC, Bhat SGT, Nakana TY, Sugihara G,
Rakshit AK (2000) Solution properties of nonionic surfactants
and their mixtures: polyoxyethylene (10) alkyl ether (CnE10) and
MEGA-10. Langmuir 16:980–987
˙
2. Akbas¸ H, Is¸can M (1994) Effect of added salt on the solubili-
zation of Sudan Red B in surfactant solution. Turk J Chem
18:80–83
3. Ribe J, Cegarra J, Aizgurua L (1983) The influence of ionic
surface-active agents on the dyeing of Hercosett wool with
a-bromoacrylamide dyes. Soc Dyers Colour 99:374–382
4. Sudbeck EA, Dubin PL, Curran ME, Skelton J (1991) Dye
solubilization in polyelectrolyte-micelle complexes. J Colloid
Interface Sci 142:512–517
5. Zana R (1998) Novel surfactants. In: C Holmberg (ed) vol 8,
p 241. Dekker, New York
It can be seen from Table 1 that the entropy values
relative to 10-2-10 are positive over the whole temperature
range studied, except at 323.15 K and that these values
decrease with an increase in temperature. This decrease in
entropy indicates that the tendency of micellization reduces
at higher temperature. Also, the enthalpy of micellization is
negative and becomes more negative with an increase in
temperature. TDSm0 ic values are smaller than DH0mic values.
6. Rosen MJ (1993) Geminis: a new generation of surfactants.
Chemtech 23:30–33
7. Swenson S (2004) Controlling surfactant self-assembly. Curr
Opin Colloid Interface Sci 9:201–212
8. Menger FM, Keiper JS (2000) Gemini surfactants. Angew Chem
Int Ed 39:1906
9. Fletcher PD (1996) Self-assembly of micelles and microemul-
sions. Curr Opin Colloid Interface Sci 1:101–106
10. Wetting SD, Verrall RE (2001) Thermodynamic studies of
aqueous m–s–m gemini surfactant systems. J Colloid Interface
Sci 235:310–316
So, the negative values of DG0mic are mainly due to DHm0 ic
.
¨
11. Akbas H, Boz M, Batıgoc¸ C¸ (2010) Study on cloud points of
With increasing temperature, the contribution of entropy to
micelle formation becomes less with a sign change in the
range from 318.15 to 323.15 K. The micelle formation
process for 10-2-10 is enthalpy—entropy driven at low
temperatures (the enthalpic contribution is 4 times larger
than the entropic contribution) and enthalpy-controlled at
high temperature. In our previous work, the study of the
thermodynamic parameters of DPC indicated that its mic-
ellization is enthalpically controlled [28].
Triton X-100-cationic gemini surfactants mixtures: a spectro-
scopic approach. Spectrochimica Acta A 75:671–677
12. Zana R, Benraou R, Rueff R (1991) Alkanediyl-a,x-bis(dim-
ethylalkylammonium bromide) surfactants. 1. Effect of the spacer
chain length on the critical micelle concentration and micelle
ionization degree. Langmuir 7:1072–1075
13. Menger FM, Keiper JS, Azov V (2000) Gemini surfactants with
acetylenic spacers. Langmuir 16:2062–2067
14. Chen L, Shi-Yow L, Chiung-Chang H, En-Ming C (1998)
Temperature dependence of critical micelle concentration
of polyoxyethylenated non-ionic surfactants. Colloid Surf A
135:175–181
15. Hunter RJ (1989) Foundations of colloid science. Oxford Uni-
versity Press, New York
Conclusions
16. Hiemenz PC, Rajagopalan R (1997) Principles of colloid and
surface chemistry. Marcel Dekker, New York
17. Wang Y, Marques EF, Pereira CM (2008) Monolayers of gemini
surfactants and their catanionic mixtures with sodium dodecyl
sulfate at the air–water interface: chain length and composition
effects. Thin Solid Films 516:7458–7466
18. Danino D, Talmon Y, Zana R (1995) Alkanediyl-a,x-bis(dim-
ethylalkylammonium bromide) surfactants (dimeric surfactants).
5. aggregation and microstructure in aqueous solutions. Langmuir
11:1448–1456
19. Diamant H, Andelman D (1994) Dimeric surfactants: spacer
chain conformation and specific area at the air/water interface.
Langmuir 10:2910–2916
Gemini surfactants are superior in their properties and
show better performance over conventional surfactants.
While the CMC values of gemini surfactants decrease
significantly with increasing alkyl chain length, those val-
ues change to a lesser degree with the spacer chain length
but are still lower than those of the corresponding mono-
meric surfactants. At a constant temperature (303.15 K),
DG0mic decreases as the hydrophobic chain length increases,
indicating that micellization is more spontaneous and that a
profound driving force due to hydrophobic interactions.
The values of DH0mic show that the micellization of gemini
20. Diamant H, Andelman D (1995) Dimeric surfactants: a simplified
model for the spacer chain. Langmuir 11:3605–3606
123

40
J Surfact Deterg (2012) 15:33–40
21. Chlebicki J, Wegrzynska J, Wilk KA (2008) Surface-active,
micellar, and anti electrostatic properties of bis-ammonium salts.
J Colloid Interface Sci 323:372–378
22. Zana R (1996) Critical micellization concentration of surfactants
in aqueous solution and free energy of micellization. Langmuir
12:1208–1211
23. Inoue T, Ebina H, Dong B, Zheng LQ (2007) Electrical con-
ductivity study on micelle formation of long-chain imidazolium
ionic liquids in aqueous solution. J Colloid Interface Sci
314:236–241
24. Alami F, Beinert G, Marie P, Zana R (1993) Alkanediyl-a,x-
bis(dimethyl alkyl ammonium bromide) surfactants. 3. Behavior
at the air-water interface. Langmuir 9:1465–1467
25. Nusselder JJH, Engberts JFN (1992) Toward a better under-
standing of the driving force for micelle formation and micellar
growth. J Colloid Interface Sci 148:353–361
26. Grosmaire L, Chorro M, Chorro C, Partyka S, Zana R (2002)
Alkanediyl-a,x-bis(dimethyl alkyl ammonium bromide) surfac-
tants 9. Effect of the spacer carbon number and temperature on the
enthalpy of micellization. J Colloid Interface Sci 246:175–181
27. Akbas¸ H, Kartal C¸ (2006) Conductometric studies of hex-
adecyltrimethylammonium bromide in aqueous solutions of eth-
anol and ethylene glycol. Colloid J 68:125–130
Author Biographies
Halide Akbas¸ is an associate professor of physical chemistry, in the
chemistry department at Trakya University. She graduated from the
Technical University of Istanbul and received her Ph.D. at Trakya
University in 1993. Her research area focuses on novel surfactants,
their thermodynamic properties and interactions, and surface
chemistry.
Aylin Elemenli was a master student in physical chemistry, in the
chemistry department at Trakya University. She received her master’s
degree in 2010 from this university. Her research focuses on dimeric
surfactants and their interaction with dyes.
Mesut Boz is an assistant professor of organic chemistry, in the
chemistry department at Trakya University. He received his M.Sc. in
1996 and his Ph.D. in 2005 at this University. His main research
interests are in organic synthesis, characterization, spectroscopy, and
recently, dimeric surfactants.
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28. Akbas¸ H, Batıgoc¸ C¸ (2008) Micellization of dodecylpyridinium
chloride in water–ethanol solutions. Colloid J 70:127–133
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