Synthesis and properties of organosilicon quaternary salts surfactants

Article abstract of DOI:10.1007/s11743-011-1306-z

Diethyl-benzyl-[3-methyldimethoxyl)]silpropyl ammonium chloride (DEBSAC) was synthesized from N,N-diethyl-aminopropyl-methyldimethoxysilane (DEAP-MDES) and benzyl chloride. Diethyl-2,3-epoxypropyl-[3-methyldimethoxyl)] silpropyl ammonium chloride (DEEPSAC) was synthesized from DEAPMDES and epoxy chloropropane. Trimethyl-[3-methyldimethoxyl)] silpropyl ammonium chloride (TMSAC) was synthesized from tri-methylamine and γ- chloropropylmethyldimethoxysilane (CPMDMS). The products were characterized by ¹H NMR, ¹³C NMR, and IR. The surface tension measurements showed that the organosilicon quaternary salts exhibit a lower surface tension and a lower critical micelle concentration (CMC) than the hydrocarbon counterparts. The plate count method experiments illustrated that DEEPSAC has a better degree of antibacterial activity against Escherichia coli than DEBSAC. The solubilizing effects of the organo-silicon quaternary salts on organosilicone were studied by pseudo-ternary phase diagrams of synthesized products/cosurfactant(n-butanol)/water/octamethylcyclotetrasiloxane. The solubilizing activities decreased in the order of TMSAC>DEBSAC>DEEPSAC.

Full text of DOI:10.1007/s11743-011-1306-z

J Surfact Deterg (2012) 15:339–344
DOI 10.1007/s11743-011-1306-z
ORIGINAL ARTICLE
Synthesis and Properties of Organosilicon Quaternary Salts
Surfactants
•
Junying Li Qingsi Zhang Yan Wang
•
•
•
Wenyu Zhang Tianduo Li
Received: 3 May 2010 / Accepted: 1 September 2011 / Published online: 5 November 2011
Ó AOCS 2011
Abstract Diethyl-benzyl-[3-methyldimethoxyl)]silpropyl
ammonium chloride (DEBSAC) was synthesized from
N,N-diethyl-aminopropyl-methyldimethoxysilane (DEAP-
MDES) and benzyl chloride. Diethyl-2,3-epoxypropyl-
[3-methyldimethoxyl)] silpropyl ammonium chloride
(DEEPSAC) was synthesized from DEAPMDES and epoxy
chloropropane. Trimethyl-[3-methyldimethoxyl)] silpropyl
ammonium chloride (TMSAC) was synthesized from tri-
methylamine and c-chloropropylmethyldimethoxysilane
(CPMDMS). The products were characterized by 1H NMR,
13C NMR, and IR. The surface tension measurements
showed that the organosilicon quaternary salts exhibit a
lower surface tension and a lower critical micelle concen-
tration (CMC) than the hydrocarbon counterparts. The plate
count method experiments illustrated that DEEPSAC has a
better degree of antibacterial activity against Escherichia
coli than DEBSAC. The solubilizing effects of the organo-
silicon quaternary salts on organosilicone were studied by
pseudo-ternary phase diagrams of synthesized products/
cosurfactant(n-butanol)/water/octamethylcyclotetrasiloxane.
The solubilizing activities decreased in the order of
TMSAC [ DEBSAC [ DEEPSAC.
Keywords Organosilicon quaternary salt ꢀ Surface
tension ꢀ Antibacterial activity ꢀ Phase behavior diagram
Introduction
Organosilicon quaternary salts are a novel type of cationic
surfactants with hydrophobic groups containing silicon.
This type of surfactant has, in general, a lower critical
micelle concentration (CMC) and provides lower surface
tensions than surfactants whose hydrophobic portions are
entirely hydrocarbon in nature. Organosilicon quaternary
salts exhibit excellent properties due to the characteristics
of organosilicon, such as thermal stability, low-temperature
flexibility, anti-static properties, water resistance, biologi-
cal and chemical inertness, and very low surface energy.
Quaternary ammonium group structure also lends to novel
antibacterial and surface activities. Thus, silicone-con-
taining cationic surfactants have excellent surface activity,
low toxicity and antimicrobial activity on Gram-positive
and Gram-negative bacteria, yeast, fungi, and mold.
Organosilicon quaternary salts have been used in the textile
industry to provide fabric for antibacterial activity, as well
as improved wicking, softness, elasticity, and anti-static
behavior. The reagents prepared by organosilicon quater-
nary salts can also be used in pesticide formulation [1–7].
Dow Corning first synthesized an organosilicon quater-
nary salt [(CH3O)3Si(CH2)3N?(CH3)2C18H37]Cl-, named
DC-5700. It is not only a novel cationic surfactant, but also
a reactive silane that is able to react with many materials,
such as glass, cotton, or polyester fibers by hydrolyzed
silanol. The treated materials show an antibacterial prop-
erty that is maintained after repeated washings [7]. The
toxicity experiments with this product indicated that the
median lethal dose is LD50 = 12.27 g/kg 0.116 g/kg,
J. Li ꢀ T. Li (&)
Shandong Provincial Key Laboratory of Fine Chemicals,
Shandong Institute of Light Industry, Jinan 250353,
People’s Republic of China
e-mail: litianduo@163.com
J. Li ꢀ Q. Zhang ꢀ W. Zhang
School of Chemical Engineering, Shandong Institute of Light
Industry, Jinan 250353, People’s Republic of China
Y. Wang
School of Food and Bioengineering, Shandong Institute of Light
Industry, Jinan 250353, People’s Republic of China
123

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J Surfact Deterg (2012) 15:339–344
and that it cannot be absorbed into the body through fin-
ished fabric. This essentially shows that the organosilicon
quaternary salt is probably a safe antibacterial agent.
Organosilicon quaternaries were prepared generally by
an Si–H addition reaction to get tertiary amino silicon,
which then reacted with haloalkane [8–10] or by the
Menschutkin reaction of halogenoalkyl silicone unit with
tertiary amines [2, 7, 11].
redistilled under vacuum, N,N-diethyl aminopropyl meth-
yldimethoxysilane (DEAPMDEOS) was provided by
Shandong Provincial Key Laboratory of Fine Chemicals,
epoxy chloropropane and benzyl chloride were purchased
from Shanghai Chemical Reagent Corporation, and redis-
tilled. 30% trimethylammonium alcohol solution was pur-
chased from Shanghai Chemical Reagent Corporation.
Octamethylcyclotetrasiloxane (D4) was purchased from
Dow Corning, and redistilled.
Hazziza-Laskar et al. [12, 13] prepared polysiloxane
quaternaries by the following three steps: the first was the
preparation of 1-(N,N-dimethylaminopropyl)1,1,3,3-tetra-
methyl disiloxane (M02A) by hydrosilylation with platinum
catalysts. The second step was the grafting of M02A onto the
1,2-units of a hydroxytelechelic polybutadiene by hydrosi-
lylation. The last step was the quaternization of the pendant
tertiary amino groups in methanol with alkyl bromides from
C8H17Br to C16H33Br. The final products were characterized
Instruments
Surface tensions were measured by the du Nou¨y ring
method on a Chengde Dingsheng JYW-200 auto interfacial
tensiometer. Fourier transform infrared (FT-IR) spectra
were obtained on a Nicolet NEXUS 470 FT-IR spectrom-
1
eter. H-NMR and 13C-NMR solution spectra were recor-
1
by H-NMR and FT-IR. A series of concentrations of the
ded on a Bruker Avance II 400 MHz NMR spectrometer.
compounds made by Hazziza-Laskar et al. were covered to
form films. It was concluded that the water solution of
1 mmol/g had good germ inhibition to Escherichia coli.
Sauvet et al. [7, 14] and Huang and Huang [11, 15]
synthesized organosilicon containing quaternary ammo-
nium salt groups by reacting polysiloxane-bearing chloro-
hydrocarbon with tertiary amine. Huang and Huang found
that the reaction is almost a second-order reaction when
chloropropyl groups have low reaction yield, and the rate
constant obviously increases when the reaction yield of
chloropropyl groups exceeds 40%. They treated 100%
cotton textiles with this compound and found that this kind
of organosilicon quaternary salt had a novel antibacteri-
cidal activity on E. coil and Staphylococcus aureus when
the mass concentration exceeds 1.5%. Sauvet et al. found
that the compounds have high antibactericidal activity in a
water solution toward E. coli and S. aureus. They also
reported that there is no essential difference in the activity
with different quaternary ammonium unit arrangement in
the compounds.
Synthesis of Trimethyl-[3-methyldimethoxyl)]silpropyl
Ammonium Chloride (TMSAC)
30% trimethylammonium ethanol solution and c-chlor-
opropylmethyldimethoxysilane were mixed in a clean, dry,
and closed reactor, with a mole ratio of the respective sub-
stances of 1.3:1. The reaction temperature was adjusted to
90 °C and the mixture was stirred for 12 h. After the com-
pletion of the reaction, the solvent and excess reactants were
evaporated. The remaining product was washed with ether
several times and dried in a vacuum oven at 40 °C. The yield
of the reaction shown in Scheme 1 was about 90%.
1H-NMR (d,ppm,D2O):
d
0.05(m,SiCH3),
d
3.0[m,N?
(CH3)3], d3.3[m,Si(OCH3)2], d0.95(m,SiCH2CH2CH2N?),
d
1.65(m,SiCH2CH2CH2N?), d2.7(m,SiCH2CH2CH2N?).
13C-NMR [d,ppm,(CD3)2SO]: d-1.3(m,SiCH3), d67[s,N?
(CH3)3], d51.5[s,Si(OCH3)2], d13.5(m,SiCH2CH2CH2N?),
d
25.6(m,SiCH2CH2CH2N?), d47.2(m,SiCH2CH2CH2N?).
In the present work, using organosilicon tertiary amine
and chloroalkane, or c-chloropropylmethyldimethoxysilane
and tertiary amine as the raw materials, a series of
organosilicon cationic surfactants have been successfully
synthesized via the Menschutkin reaction, through a one-
step reaction without catalyst. The surface activity, anti-
bacterial property, and solubilization are reported.
Synthesis of Diethyl-benzyl-[3-methyldimethoxyl)]
silpropyl Ammonium Chloride (DEBSAC)
DEAPMDEOS and anhydrous ethanol were mixed into a
100-mL, four-necked flask equipped with N2 protection,
stirring, thermometer, and reflux condenser. The mixture
temperature was adjusted to reflux and benzyl chloride was
Experimental Procedures
Materials
c-Chloropropylmethyldimethoxysilane was purchased from
Nanjing Yudeheng Coupling Reagent Corporation,
Scheme 1 Synthesis of trimethyl-[3-methyldimethoxyl)] silpropyl
ammonium chloride (TMSAC)
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341
added dropwise. The mole ratio of DEAPMDEOS to
benzyl chloride is 1:1.2. The mixture was refluxed at 80 °C
for 22 h. After the completion of the reaction, the solvent
and excess reactant were evaporated under high vacuum.
The remaining product is light-yellow and water-soluble.
The reaction equation is shown in Scheme 2.
Scheme 3 Synthesis of diethyl-2,3-epoxypropyl-[3-methyldimeth-
oxyl)] silpropyl ammonium chloride (DEEPSAC)
IR (KBr smear): 1,629.12 and 3,196.76 cm-1 are char-
acteristic of benzene, 2,955.90 cm-1(mCH3), 1,456.02 cm-1
(dCH2), 1,397.04 cm-1(dCH3), 2,904.95 cm-1(mN–CH2),
796.78 cm-1(dN–CH2), 1,198.87 cm-1(mN–C), 1,260.30 cm-1
(mSiC), 1,081.51 cm-1(mSiO).
d3.1(m,
), d1.65(m,N?CH2—), d1.15[m,N?(CH2
CH2CH
O
1H-NMR (d,ppm,CD3Cl): d1.38[m,N?(CH2CH3)2], d3.22
[m,N?(CH2CH3)2], d2.0(m,N?CH2CH2CH2Si), d4.60(m,N?
CH2C6H5), d0.61(m,N?CH2CH2CH2Si), d1.05(m,N?CH2CH2
CH3)2], d3.14(m,
).
CH2CH
O
13CNMR
[d,ppm,(CD3)2SO]:
d
-1.43(m,SiCH3),
d0.19(m,SiCH3), d
7.3–7.4(s,s N?CH2C6H5), d3.51
d
6.77(m,SiCH2),
d
53.2(s,SiOCH3),
d
14.76(m,N?CH2CH2
CH2Si),
(m,SiOCH3).
13C-NMR [d,ppm,(CD3)2SO]: d58.85[d,N?(CH2CH3)2],
12.68[m,N?(CH2CH3)2], 60.15(m,N?CH2CH2CH2Si),
45.43(d,N?CH2C6H5), d7.49(m,N?CH2CH2CH2Si), d-1.17
CH2Si), d64.98
d
12.46[m,N?(CH2CH3)2],
58.19[m,N?(CH2CH3)2],
(s,CH2CH
),
d
d
d
O
d
d
59.55(m,N?CH2CH2CH2Si),
d
(m,SiCH3), d15.29(m,N?CH2CH2CH2Si), d132.31[s,N?CH2
C(CH)2(CH)2CH],
d
52.35(s,SiOCH3),
d
129.92[s,N?CH2
63.17(s, N+
), 73.84(s,CH2CH
).
d
CH2CH CH2
C(CH)2(CH)2CH], d128.26[s,N?CH2C(CH)2(CH)2CH], d127.75
[m,N?CH2C(CH)2(CH)2CH].
O
O
Measurements
Synthesis of Diethyl-2,3-epoxypropyl-[3-
methyldimethoxyl)] silpropyl Ammonium Chloride
(DEEPSAC)
Surface tensions of aqueous solutions of the surfactants
were measured with the ring tensiometer technique.
The antibacterial activity of the water-soluble DEBSAC,
DEEPSAC, and TMSAC was determined by testing dif-
ferent concentrations of the compounds against E. coli and
Aspergillus flavus with broth-dilution and spread-plate
methods. Surfactants solutions at a range of concentrations
were prepared with sterile, double-deionized water in
multiwell microtiter plates. The test organisms were added.
The microtiter plates were incubated at 37 °C for 24 h in a
shaker. At the end of this period, a small amount of the
mixture from each sample was withdrawn and spread on
agar plates with a swap, and the plates were incubated at
37 °C for 48 h. The growth of bacterial cells on agar plates
was observed in order to determine the corresponding
activity.
DEAPMDEOS and anhydrous methanol were added into a
100-mL, four-necked flask equipped with N2 protection,
stirring, thermometer, and reflux condenser. The tempera-
ture was adjusted to 60 °C and a mixture of epoxy chlo-
ropropane and anhydrous methanol was added dropwise
(the mole ratio of DEAPMDEOS and epoxy chloropropane
is 1:1.2). The reaction was maintained at 60 °C for 6 h.
After the completion of the reaction, the solvent methanol
was evaporated. The left product was washed four times
with ether and dried in a vacuum oven for 5 h. The reaction
equation is shown in Scheme 3.
IR (KBr smear): 920 and 775 cm-1 are characteristic of
epoxy, 2,955.67 cm-1(mCH3), 2,988.01 cm-1(mCH2), 1,482.55
cm-1(dCH3), 2,904.95 cm-1(mN–CH2), 799.83 cm-1(dN–CH2),
1,201.46 cm-1(mN–C), 1,282.47 cm-1(mSiC), 1,085.47 cm-1
(mSiO).
The phase diagram of the pseudo-ternary systems water-
octamethyl cyclotetrasiloxane(D4)-surfactant-cosurfactant
were obtained with the cloud point technique. Active
mixture (AM) and D4 were added into a bottle with a water
jacket and kept under electromagnetic stirring for 30 min;
1H-NMR (d,ppm,CD3OD),
d0.025(m,SiCH3), d0.45
(m,SiCH2), d0.97(m,N?CH2CH2CH2Si), d3.29(m,SiOCH3),
Scheme 2 Synthesis of diethyl-
benzyl-[3-methyldimethoxyl)]
silpropyl ammonium chloride
(DEBSAC)
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J Surfact Deterg (2012) 15:339–344
then, water was added dropwise in the AM/D4 mixture
until the solution visually turned cloudy.
Results and Discussion
Surface Tension
Organosilicons are very hydrophobic, but their water sol-
ubility is greatly increased by the quaternization. Figure 1
shows that DEBSAC, TMSAC, and DEEPSAC have
typical surface activity. The concentration at which the
surface tension stops dropping is the CMC. Figure 1 shows
that the CMC is about 0.0166 mol/L, 0.0182 mol/L, and
0.0275 mol/L for DEBSAC, DEEPSAC, and TMSAC,
respectively. The minimum of the surface tension is about
30, 36, and 38 mN/m for DEEPSAC, TMSAC, and DEB-
SAC, respectively, which indicates that the ability of the
reduction of the surface tension is in the order of
DEEPSAC [ TMSAC [ DEBSAC.
Fig. 2 Bactericidal activity of DEEPSAC against E. coli
Antibacterial Activity
The bactericidal activity of the aqueous solution of
DEEPSAC and DEBSAC against E. coli was determined
with plate count methods (Figs. 2 and 3). The antibacteri-
cidal activity exceeds 5 orders of magnitude (indicated as a
log reduction) when the weight concentration of DEEP-
SAC in solution is only 0.1%; in comparison with DEB-
SAC, its bactericidal activity is a 1.1 log reduction when
the concentration is 0.12%. TMSAC has no antibacterial
activity against E. coli. Consequently, the structure of the
alkyl chain bonded to N? has a considerable influence on
the antibacterial activity. When the alkyl chain bonded to
N? is an epoxypropyl, it has a very strong antibacterial
Fig. 3 Bactericidal activity of DEBSAC against E. coli
activity against E. coli, whereas benzyl takes the second
place. When the alkyl chain bonded to N? is a simple
methyl, there is no antibacterial activity against E. coli.
Regarding the antibacterial mechanism of DEEPSAC
and DEBSAC, it is generally agreed that the compounds
adsorb onto the bacterial cells surface, diffuse through the
cell wall, bind to the cytoplasmic membrane, and disrupt
the cytoplasmic membrane [16]. DEEPSAC can tightly
bond to the bacterial cell surface by the epoxy group
reacting with the hydroxyl and amino of cells, hence,
resulting in an excellent antibacterial activity against
E. coli compared to DEBSAC.
Phase Diagrams of Pseudo-Ternary Systems
TMSAC, DEBSAC, and DEEPSAC are organosilicon
cationic surfactants. A microemulsion can be obtained by
Fig. 1 Surface tension of the organosilicon quaternary salts
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343
as the oil phase, the solubilizing effects of the surfactants
on organosilicon were studied. Phase diagrams involving
D4, water, and the AM are shown in Figs. 4, 5, and 6. The
concentration of every organosilicon cationic surfactant is
10 wt% in AM. The temperature is 45 °C. In Figs. 4, 5, and
6, the region a is the microemulsion phase zone where the
system remains monophasic. The area of region a is in the
order of TMSAC [ DEBSAC [ DEEPSAC and, thus,
indicates that TMSAC has the strongest ability to form a
microemulsion. The three compounds have the same silane
group, but different cationic groups. TMSAC has the best
water solubilization power due to its more hydrophilic
cationic group.
Fig. 4 Pseudo-ternary phase diagram of AM (10% TMSAC ? 90%
n-butanol)/D4/H2O
Acknowledgments The authors are grateful to the Shandong Pro-
vincial Key Laboratory of Fine Chemicals in China. This project was
supported by the Key Grant Project of Chinese Ministry of Education
(Nr. 208073) and Shandong Province Natural Science Foundation of
China (Nr. Y2008B35).
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Wenyu Zhang is an Associate Professor at the School of Chemical
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Tianduo Li is a Professor at the School of Chemical Engineering and
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Author Biographies
Junying Li received her bachelor’s degree from Tianjin University of
Science and Technology and her master’s degree from Shandong
University in China. She is an associate professor at the School of
Chemical Engineering and Shandong Provincial Key Laboratory of
123