Synthesis and properties of novel alkyl sulfonate gemini surfactants

Article abstract of DOI:10.1007/s11743-010-1188-5

A series of novel dialkyl disulfonate gemini surfactants (2C _n-SCT where n is the carbon number of the hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by ¹H NMR, ¹³C NMR, IR spectra, and ESI-MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25 °C were determined by surface tension and electrical conductivity methods. With the increasing length of the carbon chain, the values of their CMC initially decreased, and then increased with an alkyl chain length of 14. The surface tension measurements of 2C_n-SCT (except for n - 14) determined that there is a low CMC, a great efficiency in lowering the surface tension, and a strong adsorption at the air-water interface. In addition, adsorption and micellization behavior of 2C_n-SCT were estimated from pC20, the minimum average area per surfactant molecule (A_min), and standard free energy micellization and adsorption (ΔG°c and ΔG°_ds). These properties are significantly influenced by the chain length n, and the adsorption is promoted more than the micellization. AOCS 2010.

Full text of DOI:10.1007/s11743-010-1188-5

J Surfact Deterg (2010) 13:353–359
DOI 10.1007/s11743-010-1188-5
ORIGINAL ARTICLE
Synthesis and Properties of Novel Alkyl Sulfonate Gemini
Surfactants
Xin Li
Duanlin Cao
•
Zhiyong Hu
•
Hailin Zhu
•
Sufen Zhao
•
Received: 10 July 2009 / Accepted: 8 February 2010 / Published online: 12 March 2010
Ó AOCS 2010
Abstract A series of novel dialkyl disulfonate gemini
surfactants (2C -SCT where n is the carbon number of the
Introduction
n
hydrophobic chain) were synthesized from cyanuric chlo-
ride, aliphatic amine and taurine. The chemical structures
Gemini surfactants represent a class of surfactants made up
of two amphiphilic moieties connected at the level of, or
very close to, the head groups by a spacer group [1]. The
current interest in such surfactants arises from three
essential properties [1, 2]. First, their CMC values are
generally one to two orders of magnitude lower than for the
corresponding conventional (monomeric) surfactants.
Secondly, they are more efficient than the corresponding
conventional surfactants in decreasing the surface tension
of water. Thirdly, aqueous solutions of some gemini sur-
factants with short spacers can have a very high viscosity
even at a relatively low surfactant concentration, whereas
the viscosity of the corresponding monomeric surfactant
solution is always low.
1
of the prepared compounds were confirmed by H NMR,
1
3
C NMR, IR spectra, and ESI–MS. Their critical micelle
concentrations (CMC) in the aqueous solutions at 25 °C
were determined by surface tension and electrical con-
ductivity methods. With the increasing length of the carbon
chain, the values of their CMC initially decreased, and then
increased with an alkyl chain length of 14. The surface
tension measurements of 2C -SCT (except for n = 14)
n
determined that there is a low CMC, a great efficiency in
lowering the surface tension, and a strong adsorption at the
air–water interface. In addition, adsorption and micelliza-
tion behavior of 2C -SCT were estimated from pC ,
n
20
the minimum average area per surfactant molecule (Amin),
and standard free energy micellization and adsorption
Most reports on cationic gemini surfactants focus on
quaternary ammonium gemini surfactants. There are rela-
tively few reports concerning anionic gemini surfactants
[3–6]. There is not enough data to establish the relationship
between the structures of anionic gemini surfactants and
their properties [6]. Thus, it is also important to synthesize
novel anionic gemini surfactants with different structures
and study their properties.
ꢀ
ꢀ
(
DG and DG ). These properties are significantly influ-
mic ads
enced by the chain length n, and the adsorption is promoted
more than the micellization.
Keywords Gemini surfactants ꢁ Synthesis ꢁ
Surface tension ꢁ Electrical conductivity
In this paper, we synthesized novel dialkyl disulfonate
gemini surfactants 2C -SCT by three-step reactions,
n
and investigated their surface properties by measuring the
surface tension (ccmc), critical micelle concentrations
(CMC), the minimum average area per surfactant molecule
(
Amin), and then calculated the standard free energy of
ꢀ
mic
ꢀ
ads
micellization and adsorption (DG ; DG ). In addition,
X. Li ꢁ Z. Hu (&) ꢁ H. Zhu ꢁ S. Zhao ꢁ D. Cao
School of Chemical Engineering and Environment,
North University of China, Taiyuan 030051,
People’s Republic of China
we discussed the effect of the chain length on the proper-
ties. The gemini surfactants possess a novel structure, as
shown in Scheme 1. The design makes use of a well-
established idea, that is, triazine works as a linkage which
e-mail: huzhiyong@nuc.edu.cn
1
23

3
54
J Surfact Deterg (2010) 13:353–359
Cl
Cl
N
Cl
N
N
N
N
N
N
CH3(CH2)nNH2
NH2CH2CH2SO3Na
CH3(CH2)nNH
N
Cl
CH3(CH2)nNH
N
NHCH2CH2SO3Na
Cl
Cl
CH3(CH2)nNH
N
NH(CH2)nCH3
N
N
N
N
N
NH2CH2CH2NH2
NHCH2CH2NH
NaSO3CH2CH2NH
NHCH2CH2SO3Na
n=5, 7, 11, 13
n n
Scheme 1 Synthesis of the C -SCT and 2C -SCT
links the hydrophilic head group, the hydrophobic tail and
a spacer group. The three chlorines of the cyanuric chloride
aliphatic amine, and recrystallized twice from heptane for
purification.
react with -NH step by step at high yield, so the reaction
2
is quite simple [7, 8].
Synthesis of Sodium 2-(4-Chloro-6-(Alkylamino)-1,3,
5-Triazine- 2-ylamino) Ethane Sulfonate (C -SCT)
n
Experimental
According to the literature [10], this class of monomeric
surfactants C -SCT was synthesized by mixing an aqueous
n
Materials and Equipment
solution of 0.1 mol of taurine and 150 mL acetone solution
of 0.11 mol of CT. The temperature was maintained at
45 °C and pH = 8, by adding 10% Na CO . The process
2
-Aliphatic amino-4,6-dichloro-1,3,5-triazine (CT) was
2
3
prepared as in previous work [9]. Taurine (ex Johnson
Matthey Corporation), ethylenediamine, acetone, heptane,
ethanol, sodium carbonate, hydrochloric acid (all from the
third reagent plant, Tianjin) were of analytical grade.
Doubly distilled water was used to prepare the solutions in
all experiments.
was monitored by TLC on silica gel plates and eluent
system acetone: toluene: water = 6:1:0.5 (by volume).
When the reaction was completed, the mixture was con-
centrated in vacuo, refrigerated and precipitated, then fil-
tered. The filter cake was washed three times with acetone.
The white solid was collected.
The solution surface tensions were measured by using a
K12 automatic tensiometer (Kr u¨ ss Corporation, Germany)
using the du Nouy ring method. The conductivity of the
surfactant solutions was measured by using a low-frequency
conductivity analyzer (Model DDS-307, Shanghai Precision
The structures and purities of prepared surfactants were
1
confirmed by H-NMR, IR spectrum and Elementary Anal-
ysis. Table 1 shows the results. When the carbon number of
hydrocarbon chains are 6, 8, 12 and 14, the monomeric
surfactants are represented by C -SCT, C -SCT, C -SCT
6
8
12
&
Scientific Instrument Corporation). Bruker ARX400
and C -SCT, respectively.
14
NMR Spectrometer (Bruker BioSpin Corporation, Switzer-
land), FTIR-8400S Spectrometer (Shimadzu Corporation,
Japan), Vario EL Spectrometer (Elementer Corporation,
Germany), and Bruker Apex IV FTMS (Bruker BioSpin
Corporation, Switzerland) were used to identify the struc-
tures and purities of the compounds.
0
0
Synthesis of Sodium 2,2 -(6,6 -(Ethane-1,2-
Diylbis(azanediyl) bis (4-(Alkylamino) -1,3,5-Triazine -6,
2-diyl)) bis (azanediyl))diethane Sulfonate (2C -SCT)
n
An aqueous solution of 0.055 mol of ethylenediamine was
added to 100 mL of an aqueous solution of 0.1 mol of Cn-
SCT. The temperature was maintained at 90 °C and
pH = 8, by adding 10% Na CO . The process was moni-
Synthesis
2
3
The four surfactants were synthesized in just three steps
following Scheme 1.
tored by TLC on silica gel plates and eluent system
methanol: toluene = 6:1 (by vol). When the reaction was
completed, the mixture was cooled to room temperature
and acidified to pH = 2 by addition of concentrated HCl.
The resulting precipitate was filtered, washed with water
Synthesis of 2-Aliphaticamino-4,6-Dichloro-1,3,5-Triazine
(
CT)
(to remove unreacted ethylenediamine and inorganic salts),
2
-Aliphaticamino-4,6-dichloro-1,3,5-triazine (CT) was
and neutralized with sodium hydroxide solution. A clear
aqueous solution was obtained, and this was concentrated
prepared in our lab by a reaction of cyanuric chloride with
1
23

J Surfact Deterg (2010) 13:353–359
355
1
Table 1 The assignment of H-NMR, IR spectra and the element analysis results of C
n
-SCT
1
-1
Compound
yield)
H NMR (400 MHz, DMSO) d/ppm
IR (KBr) m/cm
Elementary analysis
(found/calculated)/%
(
C
H
N
C
C
C
C
6
-SCT
85%)
0.83 * 0.86(t,3H), 1.25(s,6H),
1.46(s,2H),2.63 * 2.67(m,2H), 3.15 * 3.25(s,2H),
3,386, 3,261, 2,930, 2,857, 1,635, 1,573, 36.47/
1,438, 1,199, 1,049, 798, 725 36.72
5.28/ 19.05/
5.33 19.47
(
3
.45 * 3.49(m,2H), 6.10(s,1H), 6.50(s,1H)
8
-SCT
82%)
0.82 * 0.84(t,3H), 1.23(s,10H), 1.44(s,2H),
2.62 * 2.66(m,2H), 3.15 * 3.26(s,2H)
3,386, 3,259, 2,923, 2,854, 1,635, 1,573, 39.87/
1,438, 1,199, 1,049, 798, 725 40.26
5.91/ 17.69/
5.98 18.06
(
3
.45 * 3.49(m,2H), 6.10(s,1H), 6.50(s,1H)
12-SCT
81%)
0.82 * 0.86(t,3H), 1.22(s,18H), 1.44(s,2H),
2.62 * 2.64((m,2H), 3.15 * 3.24(s,2H),
3,249, 3,386, 2,920, 2,850, 1,620, 1,573, 45.64/
1,435, 1,199, 1,049, 798, 725 45.99
6.99/ 15.52/
7.04 15.77
(
3
.45 * 3.49(m,2H), 6.10(s,1H), 6.50(s,1H)
14-SCT
78%)
0.82 * 0.84(t,3H), 1.22(s,22H), 1.44(s,2H),
2.62 * 2.64((m,2H), 3.15 * 3.24(s,2H),
3,249, 3,386, 2,920, 2,851, 1,632, 1,573, 48.01/
1,438, 1,199, 1,049, 798, 725 48.35
7.42/ 14.61/
7.47 14.84
(
3
.45 * 3.47(m,2H), 6.10(s,1H), 6.60(s,1H)
in vacuo and refrigerated to obtain the solid products. The
products were recrystallized twice from ethanol and kept
for use.
solutions were measured at 25 °C. The curves of surface
tension versus log of surfactant concentrations (c * logC)
were plotted and their CMC values were determined from the
break points. At the same time the surface tensions corre-
sponding to CMC, ccmc, were also obtained on the curves of
c * logC.
The structures and purities of prepared surfactants were
1
13
confirmed by H NMR, C NMR, IR spectra and ESI–MS.
Table 2 shows the results. When the carbon number of
hydrocarbon chains are 6, 8, 12 and 14, the surfactants are
referred to as 2C -SCT, 2C -SCT, 2C -SCT and 2C -
Conductivity Measurement
6
8
12
14
SCT, respectively.
CMC values were also determined using the electrical
conductivity method. Conductivity of the surfactant solu-
tions was measured as a function of concentration with by
using a low-frequency conductivity analyzer at 25 °C, and
the measurement was repeated twice. The error of electri-
cal conductivity value is ± 0.2 ls/cm. The CMC was
determined as the concentration at the intersection of the
liner portions of the plots.
Surface Tension Measurements
CMC values were determined by the surface-tension
method. Measurements were taken until constant surface
tension values indicated that equilibrium with an experi-
mental error within 0.2 mN/m had been reached. For the four
gemini surfactants, the surface tensions of their aqueous
1 13
Table 2 The assignment of H NMR, C NMR, IR spectra and ESI–MS results of 2C
n
-SCT
1
13
-1
Compound H NMR (400 MHz, DMSO) d/ppm
yield)
C NMR (400 MHz, DMSO) d/ppm
IR (KBr) m/cm
ESI–MS
(positive)
m/z
(
2
2
2
2
C
6
-SCT
0.84 * 0.86(t,6H), 1.25(s,12H), 1.44(s,4H),
2.63(m,4H), 3.14(s,4H) 3.18 * 3.37(m,4H),
14.08(q), 22.25(t), 26.29(t), 29.46(t),
31.24(t), 36.86(t), 50.78(t), 165.48(s),
165.73(s)
3,399, 2,927, 2,856,
1,576, 1,522, 1,448,
1,184, 1,050, 752
707.28229
[M ? H]
?
?
?
?
(
64%)
3
.47(m,4H), 6.27 * 6.52 (s,6H)
C
8
-SCT
0.83 * 0.85(t,6H), 1.24(s,20H), 1.44(s,4H),
2.63(m,4H), 3.13(s,4H), 3.18 * 3.35(m,4H),
3
14.09(q), 22.23(t), 26.63(t), 28.87(t),
29.48(t), 31.39(t), 36.86(t), 50.75(t),
165.48(s), 165.77(s)
3,412, 2,925, 2,853,
1,576, 1,517, 1,448,
1,192, 1,051, 752
763.34352
[M ? H]
(
67%)
.46(m,4H), 6.26 * 6.51 (s,6H)
12-SCT 0.83 * 0.86(t,6H), 1.23(s,36H), 1.43(s,4H),
73%) 2.61((m,4H), 3.12(s,4H), 3.19 * 3.36(s,4H)
.46(m,4H), 6.26 * 6.50(s,6H)
14-SCT 0.83 * 0.86(t,6H), 1.23(s,44H), 1.42(s,4H),
2.60(m,4H), 3.12(s,4H), 3.20 * 3.35(s,4H)
.45(m,4H), 6.26 * 6.50(s,6H)
C
(
14.08(q), 22.23(t), 26.64(t), 28.87(t),
29.05(t), 29.49(t), 31.44(t), 36.85(t),
50.77(t), 165.47(s), 165.70(s)
3,408, 2,919, 2,851,
1,582, 1,521, 1,452,
1,186, 1,051, 755
875.46772
[M ? H]
3
C
14.05(q), 22.24(t), 26.67(t), 28.88(t),
29.08(t), 29.51(t), 31.46(t), 36.83(t),
50.78(t), 165.48(s), 165.69(s)
3,400, 2,917, 2,850,
1,577, 1,513, 1,468,
1,185, 1,050, 753
931.53022
[M ? H]
(
90%)
3
1
23

3
56
J Surfact Deterg (2010) 13:353–359
Result and Discussion
Table 3 lists the values of the CMC, ccmc, pC , Cmax,
20
Amin of 2C -SCT, along with the data of corresponding
n
Critical Micellar Concentration (CMC) and Surface
monomeric surfactants C -SCT [10] and sodium dodecyl
n
Tension (ccmc
)
sulfate (SDS) [11]. These results indicate that the CMC
values of gemini surfactants 2C -SCT and 2C -SCT are
8
12
The surface tensions of aqueous solutions of gemini sur-
about one or two orders of magnitude lower than those of
the corresponding monomeric surfactants. The low CMC
values of dimeric surfactants with respect to the corre-
sponding conventional surfactants arise mainly because
two alkyl chains, rather than one, are transferred at a
time to the water in the micelle pseudo-phase [12],
whereas the gemini surfactant 2C -SCT gives higher
factants 2C -SCT were measured at 25 °C. The results of
n
surface tension measurements are shown in Fig. 1. The
surface tensions decrease with increasing concentrations
and then reach clear break points, which are taken as CMC.
The maximum surface excess, Cmax, at the air–water
interface was calculated by applying the Gibbs adsorption
isotherm equation [11],
1
4
CMC and inferior efficiency in reducing the surface
tension than the corresponding monomeric surfactant
C -SCT.
ꢀ
ꢁ
1
dc
:303nRT d log C
Cmax ¼ ꢂ2
ð1Þ
1
4
T
The CMC of the conventional ionic surfactant is known to
-
1
where c is the equilibrium surface tension in mN m , Cmax
is the saturation adsorbed amount in mol/1,000 m , R is
decrease with increasing number of carbon atoms in the
2
hydrophobic groups up to about a hexadecyl group [6]. In this
-4
-
1
-1
the gas constant (8.314 J mol
K
), T is the absolute
work, the CMC of 2C -SCT decrease from 8.92 9 10 to
n
-
5
-1
temperature, C is the surfactant concentration, and (dc/
d logC) is the slope in the surface tension isotherm when
the concentration is near the CMC. The value of n is taken
as three for a dimeric surfactant made up of a divalent
surfactant ion and two univalent counterions in the absence
of a swamping electrolyte. In order to extract the minimum
3.34 9 10 mol L with increasing the hydrocarbon chain
from 6 to 12, which is similar to those common surfactants in
a homologous serious. However, when the carbon number
-
5
is up to 14, the CMC increases form 3.34 9 10 to 1.32 9
-1
-
10 mol L
4
.
It may be resulted from the conformation of the sur-
factants at the interface or the curling of the two hydro-
phobic chain during dissolution. The formation of the
micelle is the joint result of the hydrophobic effect and
intermolecular force between surfactants. On the view of
2
surface area occupied by a surfactant molecule, Amin (nm ),
at the air–water interface when the surface adsorption was
saturated, Eq. 2 was used,
014
NACmax
1
Amin ¼
ð2Þ
the conformation of 2C -SCT, two hydrophobic carbon
n
chains are not parallel due to the presence of several
nitrogen atoms in their structures. The interaction, such as
curling, between the hydrophobic carbon chains of the two
surfactants may hinder the formation of the micelle. This
interaction appears be stronger when the carbon number is
where N is Avogadro’s number. When C
is in
A
max
-
mol cm , Amin is in nm .
2
2
1
4, thus 2C -SCT gives higher CMC.
14
80
70
60
50
40
30
The ccmc of 2C -SCT is lower than that of the corre-
8
2
2
2
2
C -SCT
6
sponding monomeric surfactant C -SCT. This shows that
8
C -SCT
8
the gemini surfactant adsorbs strongly at the air–water
interface, and orients itself so as to cause effective surface
activity. The increase in the hydrophobic chain length
form 12 to 14 renders them slight less surface active,
probably due to a strong cohesion by two long hydrocar-
bon chains [6].
C -SCT
1
2
C -SCT
1
4
Efficiency (pC ) and Minimum Surface Area (Amin)
2
0
The efficiency can be characterized by the value of loga-
rithm of the surfactant concentration C20 at which the
-7
-6
-5
-4
-3
-2
-1
-
surface tension of water is reduced by 20 mN m . The
1
-1
logC/ (mol L )
pC20 (-logC ) value measures the efficiency of adsorption
20
of surfactant at the air–water interface; the larger the value
n
Fig. 1 Evaluation of the CMC values of 2C -SCT solutions by means
of a surface-tension method
of pC , the greater the tendency of the surfactant to adsorb
2
0
1
23

J Surfact Deterg (2010) 13:353–359
357
Table 3 Surfactant data for the eight surfactants solution at 25 °C
-
1
)
-1
-10
max/(10
-2
)
2
Surfactant
CMC/(mmol L
c
cmc/(mN m
)
pC20
C
mol cm
A
min/(nm )
Reference
2
2
2
2
C
C
C
C
6
-SCT
-SCT
0.892
0.0842
0.0334
0.132
6.19
35.64
33.57
43.87
49.39
39.21
38.48
32.53
32.5
3.99
5.04
4.72
3.98
2.81
4.37
5.01
2.5
1.02
1.11
1.97
1.16
1.89
1.94
3.07
3.16
1.63
1.50
0.84
1.44
0.88
0.86
0.54
0.53
This paper
This paper
This paper
This paper
[10]
8
12-SCT
14-SCT
-SCT
C
C
C
8
12-SCT
14-SCT
0.177
0.0358
8.2
[10]
[10]
SDS
[11]
at the air–water interface, relative to its tendency to form
micelles, and the more efficiently it reduces the surface
2C -SCT with the n of 6–12 are much larger. This indicates
n
that the anionic gemini surfactants are superior in their
efficiency at reducing surface tension.
tension [11]. The values of pC20 of 2C -SCT are also listed
n
in Table 3. The values of pC20 of 2C -SCT decrease with
n
The minimum surface area (Amin) is the surface area
demand per molecule on the air–water interface. Both Cmax
and Amin values are listed in Table 3. The Amin values of
increasing hydrocarbon chain length from 8 to 14, This
result suggests that the longer the hydrocarbon chains of
the anionic gemini surfactants, the weaker the adsorption at
the air–water interface. Compared with the corresponding
monomeric surfactants and SDS, the values of pC20 of
2C -SCT decrease with increasing hydrocarbon chain
n
length from 8 to12, and then increase when the carbon
number is up to 14. This result suggests that the gemini
5
4
3
2
1
00
00
00
00
00
0
8
7
6
0
0
0
2
C -SCT
6
2C -SCT
8
50
40
30
20
10
0
cmc conductance
cmc conductance
0
.0
0.1
0.2
0.3
0.4
0.5
0
1
2
3
4
5
-
1
-1
C / (mmol L )
C / (mmol L )
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
2
C12-SCT
2C14-SCT
200
150
1
00
50
cmc conductance
cmc conductance
0
0
.0
0.1
0.2
0.3
0.4
0.5
0.0
0.5
1.0
1.5
2.0
-
1
-1
C / (mmol L )
C / (mmol L )
Fig. 2 Electrical conductivity against molality of 2C
n
-SCT at 25 °C
1
23

3
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J Surfact Deterg (2010) 13:353–359
ꢀ
mic
ꢀ
ads
Table 4 Standard free energy of micellization and adsorption of
-SCT
The values of DG and DG of the anionic gemini
2C
n
surfactants 2C -SCT with n of 6–14 are listed in Table 4.
n
ꢀ
mic
ꢀ
ads
ꢀ
mic
ꢀ
ads
The negative values of DG and DG
anionic gemini surfactants have great ability to form
mean that the
Surfactant
CMC/
mmol L
a
DG
/
DG
/
-
1
)
-1
)
-1
(
(kJꢁmol
(kJꢁmol
)
micelles in solution and to adsorb at the air–water inter-
2C
2C
2C
2C
6
-SCT
-SCT
0.906
0.61
0.45
0.40
0.52
-23.64
-33.77
-37.53
-30.35
-59.29
-68.39
-51.81
-49.84
ꢀ
mic
face. The values of DG are also smaller than the values
8
0.0892
0.0399
0.148
ꢀ
ads
of DG in all the series, indicating that the adsorption is
promoted more than the micellization. This result is sup-
12-SCT
14-SCT
ported by the values of large pC as described above. In
2
0
ꢀ
mic
addition, the values of DG (expect for n = 14) increase
with increasing hydrocarbon chain length of the gemini
surfactants, suggesting that a driving force of micellization
is derived from the hydrophobic moieties due to the
interaction between hydrocarbon tails.
surfactant 2C -SCT packs loosely at the air–water inter-
1
4
face. A possible explanation is that the longer hydrophobic
chains are more prone to bend and thus make the Amin
value larger [14].
Acknowledgments This work was financially supported by the
Natural Science Foundation of the North University of China.
Degree of Counterion Binding to Micelles (b)
In order to study the aggregation behavior of 2C -SCT in
n
aqueous solutions, the electrical conductivity (j) of these
solutions was measured. The changes in j as a function of
concentration are shown in Fig. 2. The CMC of 2C -SCT
References
1
2
3
. Zana R, Xia J (2004) Gemini surfactants: synthesis, interfacial
and solution-phase behavior, and applications. Marcel Dekker,
New York
. Zana R (2002) Dimeric (Gemini) surfactants: effect of spacer
group on the association behavior in aqueous solution. J Colloid
Interface Sci 248:203–220
. Zhu YP, Masuyama A, Okahara M (1990) Preparation and
properties of double or triple chain surfactants with two sulfonate
groups derived from N-acyldicthanolamines. J Am Oil Chem Soc
67:459–463
n
estimated from electrical conductivity plots are listed in
Table 4. It can be seen that the values of CMC measured
from electrical conductivity at 25 °C are in agreement with
those obtained from surface tension. The degree of ioni-
zation of the micelle (a) can be obtained from the ratio of
the slopes of the linear segments above and below CMC
from conductivity versus molality plots. The values of a
are listed in Table 4. According to a values, we can obtain
b (b = 1 - a) values of 0.39, 0.55, 0.60, and 0.48 for 2C6-
4
. Magdassi S, Ben Moshe M, Talmon Y, Danino D (2003) Micro-
emulsions based on anionic gemini surfactant. Colloids Surf A
2
12:1–7
SCT, 2C -SCT, 2C -SCT and 2C -SCT, respectively.
8
12
14
5. Du X, Lu Y, Li L, Wang J, Yang Z (2007) Synthesis and unusual
properties of novel alkylbenzene sulfonate gemini surfactants.
Colloids Surf A 290:132–137
6. Yoshimura T, Esumi K (2004) Synthesis and surface properties of
anionic gemini surfactants with amide groups. J Colloid Interface
Sci 276:231–238
7. Petrova M, Konstantinova TN (2005) On the synthesis of some
reactive triazine azo dyes containing tetramethylpiperidine frag-
ment. Dyes Pigm 67:63–69
Standard Free Energy of Micellization and Adsorption
ꢀ
mic
ꢀ
ads
(
DG and DG
)
ꢀ
The standard free energy of micellization, DGmic, for ionic
Gemini surfactants can be calculated by using the equation
proposed by Zana [12]
ꢀ
8
. Konstantionova TN, Petrova P (2002) On the synthesis of some
bifunctional reactive triazine dyes. Dyes Pigm 52:115–120
. Chen L, Hu Z, Zhu H, Xue Z (2008) Synthesis of cleavable aryl
sulfonate anionic surfactants and study on their surface activity.
J Surfact Deterg 11:97–102
DG ¼ RTð1=2 þ bÞ ln cmc ꢂ ðRT=2Þ ln 2:
ð3Þ
mic
9
ꢀ
mic
-
2
-1
When the CMC is less than 10 mol L , DG can be
approximated without a significant error by Eq. 4
ꢀ
1
0. Xue Z, Hu Z, Zhu H, Chen L (2008) Synthesis and surface
activity properties of cleavable s-triazine fatty sulfonate surfac-
tants. China Surfactant Detergent Cosmet 3:151–155
1. Rosen MJ (1989) Surfactants and interfacial phenomena, 2nd
edn. Wiley, New York
DG ¼ RTð1=2 þ bÞ lnðcmc=55:3Þ ꢂ ðRT=2Þ ln 2:
ð4Þ
mic
ꢀ
ads
1
1
The standard free energy of adsorption, DG , at the
air–water interface is calculated by Eq. 5 [13]
ꢀ
2. Zana R (1996) Critical micellization concentration of surfactants
in aqueous solution and free energy of micellization. Langmuir
ꢀ
DG ¼ DG ꢂ pcmc=Ccmc
ð5Þ
ads
mic
1
2:1208–1211
1
3. Yoshimura T, Sakato A, Tsuchiya K, Ohkubo T, Sakai H, Abe
M, Esumi K (2007) Adsorption and aggregation properties of
amino acid-based N-alkyl cysteine monomeric and N, N’-dial-
kyl cysteine gemini surfactants. J Colloid Interface Sci 308:
466–473
where pcmc represents the surface pressure at the CMC
(
pcmc = c - c , c and c represent the surface tension
0
cmc
0
cmc
of water and the surfactant solution at the CMC,
respectively).
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J Surfact Deterg (2010) 13:353–359
359
1
4. Ao M, Xu G, Zhu Y, Bai Y (2008) Synthesis and properties of
ionic liquid-type gemini imidazolium surfactant. J Colloid
Interface Sci 326:490–495
Hailin Zhu is currently an assistant teacher at the School of Chemical
Engineering and Environment, North University of China. She
received her M.Sc. in Chemical Technology at School of Chemical
Engineering of Zhengzhou University—China. Her research interest
is in the synthesis and properties of fine chemicals.
Author Biographies
Sufen Zhao is a Master’s student at the School of Chemical
Engineering and Environment, North University of China. Her
research interests deal with the synthesis and properties of surfactants.
Xin Li is a Master’s student at the School of Chemical Engineering
and Environment,North University of China. Her research deals with
the synthesis and the properties of surfactants.
Duanlin Cao is currently a Professor at the School of Chemical
Engineering and Environment, North University of China. He
received his M.Sc. in Organic Chemistry at Nanjing University of
Technology and his Ph.D. in Applied Chemistry at Tianjin University.
His research interests include green chemistry, supramolecules
chemistry, and organic synthesis.
Zhiyong Hu is currently a teacher at the School of Chemical
Engineering and Environment, North University of China. He received
his M.Sc. in Organic Chemical Technology at Taiyuan University of
Technology and his Ph.D. in Applied Chemistry at State Key
Laboratory of Fine Chemicals, Dalian University of Technology—
China. His research interests include synthesis and application of green
surfactants, chemically modified natural polysaccharides.
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