Morphology-controlled synthesis of poly (oxyethylene) silicone or alkylsilicone surfactants with explicit, atomically defined, branched, hydrophobic tails

Article abstract of DOI:10.1002/chem.201103093

Silicone surfactants are widely used in commerce because of the unusual surface activity when compared with fluorocarbon or hydrocarbon surfactants. However, most silicone surfactants are comprised of ill-defined mixtures, which preclude the development o

Full text of DOI:10.1002/chem.201103093

DOI: 10.1002/chem.201103093
Morphology-Controlled Synthesis of Poly(oxyethylene)silicone or
Alkylsilicone Surfactants with Explicit, Atomically Defined, Branched,
Hydrophobic Tails
Ferdinand Gonzaga,* John B. Grande, and Michael A. Brook*[a]
Abstract: Silicone surfactants are
widely used in commerce because of
the unusual surface activity when com-
pared with fluorocarbon or hydrocar-
bon surfactants. However, most silicone
surfactants are comprised of ill-defined
mixtures, which preclude the develop-
ment of an understanding of structure–
surface activity relationships. Herein,
we report a synthetic strategy that per-
mits exquisite control over silicone
drophobes were then mated to hydro-
philic poly(oxyethylene)s of three dif-
ferent molecular weights by a metal-
free click cyclization to generate a li-
brary of explicit silicone surfactants.
These compounds were calculated to
have a relatively linear value range of
the hydrophilic–lipophilic balance,
ranging from about 8 to about 15. The
solubility of some of the compounds
was too low to measure a critical mi-
celle concentration (CMC). The others
exhibited a broad range of surface ten-
sion values at the CMC that depend
both on the length of the hydrophilic
tail and, more importantly, the nature
of the hydrophobic head group. Subtle
distinctions in surfactant-related prop-
erties, which can be attributed to the
three-dimensional structures, can be
seen for compounds with comparable
numbers of hydrocarbons and silicon
groups.
Keywords: click chemistry · poly-
(oxyethylene) · silicone · surfac-
tants · borane
structure by using the BACHTNUTRGNE(UNG C6F5)3-cata-
lyzed condensation of hydro- and al-
koxysilanes. Six different, precise hy-
Introduction
Poly(oxyethylene) monoalkyl ethers are the most widely
used nonionic surfactants. These surfactants, both oligomeric
and polymeric, find applications in consumer products, par-
ticularly personal-care products, and a wide variety of indus-
trial processes.[1] For surfactant design for specific purposes,
advantage is taken of the well-established correlation be-
tween surface activity and sizes and structures of both the
alkyl group and the poly(oxyethylene) hydrophile.
Scheme 1. Typical silicone surfactants: A) superwetters and B) rake co-
polymers.
Silicone-based silicone surfactants, which have hydro-
phobes of much lower surface energy than alkanes, have re-
markable surface-activity properties. For example, dilute
aqueous solutions of superwetters (for an example see
Scheme 1A), which are commonly used to disperse agricul-
tural chemicals on leaves, can rapidly spread across waxy
leaves to 50 times the original droplet size.[2,3] With the ex-
ception of some silicone surfactants that are based on small,
well-defined siloxanes, most silicone surfactants involve ill-
defined mixtures of silicone polymers modified by oligo- or
poly(ethylene glycol) (PEG) or propylene glycol (PPG)
chains (Scheme 1B).[4] For the most part, this is because reli-
able syntheses for explicit silicones do not exist.
The nature of surfactant aggregates found in solution
strongly depends on geometric constraints during self-as-
sembly, which derive from structural parameters, such as the
volume and length of the apolar constituent.[5,6] Whereas the
tailoring of the polar head groups of surfactants is a very
widespread and usual feature in surfactant design, the fine-
tuning of the hydrophobic tails has proven considerably
more challenging. In the hydrocarbon series, functionalized-
precursors (such as, iodo or bromo, alkyne or alkene) that
would allow the creation of branching units or the introduc-
tion of aromatic systems (e.g., phenyl groups) or reactive
groups (such as, allyl groups) at precisely defined positions
in the hydrocarbon chain are not always available. The sili-
cone series has a similar problem regarding controlled syn-
thesis of the hydrophobe. In addition, and more problemat-
[a] Dr. F. Gonzaga,+ J. B. Grande,+ Prof. Dr. M. A. Brook
Department of Chemistry and Chemical Biology
McMaster University, 1280 Main Street W.
Hamilton ON L8S4 M1 (Canada)
Fax : (+1)905-522-2509
E-mail: mabrook@mcmaster.ca
gonzaga@mcmaster.ca
[+] These two authors contributed equally to this work.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201103093.
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Chem. Eur. J. 2012, 18, 1536 – 1541

FULL PAPER
ic, is the fragility of silicone intermediates and products to
acid- and base-catalyzed redistribution and other degrada-
tion reactions.[7] Even in cases for which it is possible to as-
semble precise, larger silicone fragments, the preservation of
these structures requires that subsequent steps are undertak-
en at neutral pH, which has proven challenging.[8]
Recently, we[9] and others[10,11,12,13] have described the
preparation of silicone polymers by using the Piers–Rubinsz-
tajn reaction.[14,15,16,17] Explicit silicone structures can be the
result of such reactions.[9] We have demonstrated the toler-
ance of BACHTUNGTRENNUNG(C6F5)3 to a variety of organic functional groups,
including allyl, chloro-, and iodoalkanes.[18] Equally impor-
tant, additional functional groups can be incorporated into
these silicones while their structures are preserved. For ex-
ample, appropriately functionalized compounds will undergo
click reactions, including metal-free addition of azides to al-
kynes and the thiolene reaction.[19]
Herein we present a general, efficient, simple, and metal-
free synthetic route to explicit silicone– or silicone–alkyl
poly(oxyethylene) surfactants. The process relies on two
separate, extremely efficient reactions: the Piers–Rubinsz-
tajn reaction[20] to create explicit silicone hydrophobes and
the Huisgen 1,3-dipolar cycloadditions of azides to al-
kynes—metal-free click chemistry—used to link the silicone
to a hydrophile. In addition to the syntheses, the critical mi-
celle concentration (CMC) and the value of surface tension
(ST) at the CMC were determined for the prepared surfac-
tants, and related to the morphologies of the surfactants.
Results and Discussion
The surfactant synthesis required independent preparation
of well-defined azidopropylsilicones and propiolate-termi-
nated PEGs, respectively. The routes to each of these key
intermediates is first outlined, followed by a description of
the coupling process, which involved a low temperature,
metal-free (and catalyst-free) cycloaddition of the hydro-
phobic azides to monopropiolate-terminated poly(oxyethy-
lene)s of various molecular weights under almost solvent-
free conditions (Scheme 2).
The hydrophobic portion of the surfactant was prepared
in two steps by starting from simple, commercially available
chloro- or iodopropylalkoxysilanes. These were coupled
with hydrosilanes by using B
a small library of complex silicones that possessed a single
alkyl halide—the Piers–Rubinsztajn reaction
ACHTNUGTRNEN(NUG C6F5)3 as a catalyst to provide
Scheme 2. a) Synthesis of explicit azidosilicones by using the Piers–Ru-
binsztajn reaction and/or nucleophilic displacement of halogens, followed
by a click ligation. b) The explicit silicone fragments.
(Scheme 2A).[21] With the exception of azide 6-N3, which
was prepared from tris(trimethylsiloxy)silane 6-Cl, all azides
1-N3 to 5-N3 were prepared in high yields (typically ranging
from 77 to 93%) by displacement of the alkyl halide by
azide. It should be noted that the synthesis of such
branched, explicit siloxane structures would be extremely te-
dious and, at the least, difficult with the use of conventional
chlorosilane chemistry. The process permits the introduction
of decreasing bulk and ramifications on the siloxane back-
bone, as shown by the comparison in the structures of azides
1-N3, 3-N3, and 6-N3, with increasing numbers of trimethyl-
silyl groups. Moreover, the functional-group tolerance[18,19]
of the Piers–Rubinsztajn reaction permitted introduction of
reactive groups, such as allyl (azide 5-N3) or a tunable
amount of phenyl moieties (azides 2-N3 and 4-N3;
Scheme 2).
Chem. Eur. J. 2012, 18, 1536 – 1541
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1537

M. A. Brook, F. Gonzaga et al.
Surfactant polar head groups were prepared from monop-
ropiolate-terminated poly(oxyethylene)s, with average mo-
lecular weights of 350, 750 and 2000. The synthetic route to
such derivatives involves a classical Fischer esterification of
the corresponding monomethoxy-terminated poly(oxyethy-
lene) derivative (Scheme 2B), followed by chromatographic
purification (for the 350- and 750-molecular-weight precur-
sors) or precipitation, for the highest-molecular-weight com-
pounds.
Propiolate esters of poly(oxyethylene) were chosen due to
the electron deficiency. We have shown previously that such
activated alkynes undergo a metal-free click reaction (1,3-di-
polar cycloaddition of azides to alkynes) at moderate
(508C) or even room temperature, without the need of a
copper catalyst.[22,23,24]
The thermal cycloaddition of mono(propiolate) esters of
poly(oxyethylene) proved to be extremely efficient; isolated
yields that ranged from 79–99% were observed (Sche-
me 2aC, Table 1). Moreover, the experimental procedure
was straightforward: simple mixing of the two precursors in
a small amount of toluene followed by mild heating allows
the chemical ligation to proceed and gives the correspond-
ing surfactants. The purification step benefits from two very
interesting factors associated with the procedure. The first is
inherent to this class of thermal cycloadditions; no byprod-
ucts are generated during the reaction. The second relies on
the fact that a small excess of the azido derivative was used.
This not only allowed the reaction to run faster and to
ensure complete conversion of the poly(oxyethylene) pro-
piolate into the surfactant, but also, due to the very large
gap in polarity between the starting azidosiloxane (very non-
polar, running with the solvent front in TLC and chromatog-
raphy) and the cycloaddition product (amphiphilic, thus
more polar), allows easy isolation of the product from the
reaction mixture (i.e., a simple “chromatographic” filtration
over silica gel; elution with CH2Cl2 eluted the azide, fol-
lowed by elution with a methanol:CH2Cl2 mixture to elute
the product). Last but not least, the entire procedure was
designed to respect the integrity of the siloxane hydrophobic
moiety. Siloxane bonds are extremely sensitive to acid- and
base-catalyzed redistribution and other degradation reac-
tions.[7] The isolated surfactants were analyzed by proton,
carbon, and silicon NMR spectroscopy, which all indicate
that the exact silicone structures of the starting azides were
preserved in the corresponding surfactants. 29Si NMR, in
that respect, was essential as it proved, without any ambigui-
À
ty, that every single M (monosiloxane R3SiO ), D (disilox-
À
À
À
ane OSiR2O ), or T (trisiloxane (RO)3Si ) unit was pre-
served during the synthetic process.
The structural diversity of the prepared surfactants is re-
flected in the aggregation properties and calculated hydro-
philic–lipophilic balance (HLB[25] and 3D-HLB)[26] values, as
shown in Table 2 and Figure 1. For example, surfactants
8PEG-6 to 13PEG-6, based on the smallest poly(oxyethy-
lene) 7PEG-6, present HLB values that range from 5.41 to
8.79 (3D-HLB, oil component values that range from 2.18 to
10.48). Such low values indicate a highly hydrophobic char-
acter. Experimentally, the following was observed: these sur-
factants were not measurably soluble in water, and thus the
CMCs could not be determined. However, this lack of aque-
ous solubility does not rule out other applications. These
amphiphilic derivatives are extremely well suited for the de-
velopment of water-in-oil emulsions (typical values of HLB
Table 1. Summary of prepared surfactants.
Table 2. CMC data for the prepared surfactants.
Surfactant
CMC
[mM]
ST at CMC
[mNmÀ1
HLB[a]
3D-HLB[26]
N
]
1
2
3
4
5
6
7
8
8PEG-6
9PEG-6
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
5.41
5.93
6.82
7.10
7.98
8.79
9.12
9.55
10.58
10.88
11.82
12.59
13.92
14.29
15.08
15.30
15.97
16.46
(5.41, 2.18)
(5.93, 10.48)
(6.82, 2.76)
(7.10, 7.71)
(7.98, 6.12)
(8.79, 3.55)
(9.12, 1.70)
(9.55, 7.78)
(10.58, 1.97)
(10.88, 5.45)
(11.82, 4.18)
(12.59, 2.35)
(13.92, 0.95)
(14.29, 4.25)
(15.08, 1.02)
(15.31, 2.80)
(15.97, 2.06)
(16.46, 1.12)
Hydrophobic tail Polar head group
n
Surfactant yield [%][a]
1
2
3
4
5
6
7
8
9
1-N3
2-N3
3-N3
7PEG-6
7PEG-15
7PEG-44
7PEG-6
7PEG-15
7PEG-44
7PEG-6
7PEG-15
7PEG-44
7PEG-6
7PEG-15
7PEG-44
7PEG-6
7PEG-15
7PEG44
7PEG-6
7PEG-15
7PEG-44
6
8PEG-6 (79%)
10PEG-6
11PEG-6
12PEG-6
13PEG-6
8PEG-15
9PEG-15
10PEG-15
11PEG-15
12PEG-15
13PEG-15
8PEG-44
9PEG-44
10PEG-44
11PEG-44
12PEG-44
13PEG-44
15 8PEG-15 (81%)
44 8PEG-44 (83%)
6
15 9PEG-15 (90%)
44 9PEG-44 (78%)
6
15 10PEG-15 (87%)
44 10PEG-44 (84%)
6
15 11PEG-15 (88%)
44 11PEG-44 (93%)
6
15 12PEG-15 (90%)
44 12PEG-44 (87%)
6
15 13PEG-15 (84%)
44 13PEG-44 (93%)
9PEG-6 (89%)
10PEG-6 (99%)
9
na
na
10
11
12
13
14
15
16
17
18
7.2ꢁ10À5
6.1ꢁ10À5
5.7ꢁ10À5
na[b]
32.3
25.0
23.7
na[b]
48.0
23.2
46.7
38.8
29.4
10 4-N3
11PEG-6 (83%)
11
12
8.3ꢁ10À5
0.9ꢁ10À3
4.0ꢁ10À5
2.4ꢁ10À5
1.2ꢁ10À3
13 5-N3
12PEG-6 (91%)
14
15
16 6-N3
13PEG-6 (88%)
17
18
[a] HLB values were calculated using Griffinꢂs method. [b] Attempts to
obtain the CMC value for this surfactant were unsuccessful, despite the
excellent solubility in water.
[a] Isolated yield.
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Silicone Surfactants
FULL PAPER
chain. Indeed, long hydrophilic ethylene-oxide chains are
not completely located in the bulk water, but can penetrate
partially into the surfactant film, thus preventing the forma-
tion of a tightly packed surfactant film. The CMC of a
MDM trisiloxane surfactant with a 16-ethylene-oxide-units
hydrophilic head group was found to be 1 mm. Surfactants
11PEG-15, 12PEG-15, and 13PEG-15 have similar hydro-
philic components, yet their CMCs are more than two
orders-of-magnitude lower than this value. Surfactant
13PEG-15 possesses a purely silicone hydrophobic tail, and
accordingly, presents a ST value (23.7 mNmÀ1) characteristic
of silicone surfactants. The substitution of a methyl group by
an allyl or a phenyl group produced an increase in the ST
value at the CMC to 25.0 (12PEG-15) and 32.3 mNmÀ1
(11PEG-15), respectively. These results indicate that even a
subtle manipulation in the morphology of the surfactants
(e.g., an allyl moiety instead of a methyl) can be used to
tailor the physical properties (Figure 1).
The ability to control the surfactant-related properties
was further highlighted by the study of the aggregation of
surfactants 8PEG-44–13PEG-44, based on the approximate
2000-molecular-weight poly(ethylene oxide) 7PEG-44.
These surfactants presented HLB values in the range 13.92–
16.46 (3D-HLB oil component values range 0.95–4.25), char-
acteristic of surfactants with good aqueous solubility and
high detergency power (i.e., able to strongly stabilize oil-in-
water emulsions). The CMC values for surfactants 10PEG-
44 and 13PEG-44 are in the millimolar range, due to the re-
duced size of the hydrophobic moieties. On the other side,
surfactants with a larger, hyperbranched hydrophobic tail,
such as 9PEG-44, 11PEG-44, and 12PEG-44, have ex-
tremely low CMC values, ranging from 24 mm for 12PEG-44
to 83 mm for 9PEG-44. Interestingly, surfactants 11PEG-44
and 12PEG-44, based on the 2000-molecular-weight poly(-
oxyethylene), exhibits CMC values (40 and 24 mm, respec-
tively) that are approximately half of those of the analogues
based on the 750-molecular-weight polyACHTNUTRGNEUNG(ethylene)oxide
11PEG-15 and 12PEG-15 (72 and 61 mm, respectively). This
behavior is unusual, as in the trisiloxane–oligo(ethylene
oxide) surfactant series it was previously shown that CMC
values increase with increasing hydrophilic chain length.
However, this effect came with a large increase of the inter-
facial tension values at the CMC (from 25.0 to 38.8 mNmÀ1,
for 12PEG-15 and 12PEG-44, respectively). Although ag-
gregation occurs at a lower concentration for higher-molecu-
lar-weight poly(oxyethylene)s, the interfacial stabilization
between water and the surfactant is not as efficient; this
effect could also reflect changes in the type of surfactant ag-
gregates that form (micelles, worm-like micelles). Values of
ST at the CMC are small for 10PEG-44 and 13PEG-44 and
characteristic of silicone surfactants: increased alkyl or aryl
character of the hydrophobic moieties also increases the ST
at the CMC (with values as high as 48.0 mNmÀ1 for 9PEG-
44).
Figure 1. ST data for two series of surfactants with different hydrophilic
tails, 7PEG-15, and 7PEG-44.
range from 4 to 6) or the wetting of powders into oil (HLB
range 7–9).
For the three water-soluble surfactants, 11PEG-15,
12PEG-15, and 13PEG-15, extremely small CMC values
were found, ranging from 57 (13PEG-15) to 72 mm (11PEG-
15). These values easily compete with existing explicit trisi-
loxane surfactants that possess various lengths of poly(oxy-
ethylene) chains. For example, an explicit MDM trisiloxane
surfactant with four ethylene-oxide units as the hydrophilic
head group have a CMC of 79 mm.[2] Moreover, it is well
known that the surface activities of siloxane surfactants de-
crease with increasing length of the poly(oxyethylene)
The surfactants based on the intermediate-chain-length
poly(oxyethylene) 7PEG-15, not surprisingly, presented an
intermediate character. Whereas aqueous solubility and thus
Chem. Eur. J. 2012, 18, 1536 – 1541
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1539

M. A. Brook, F. Gonzaga et al.
The resulting solution was filtered and concentrated under reduced pres-
micellization could be observed for the more hydrophilic
surfactants, such as 11PEG-15, 12PEG-15, and 13PEG-15
(HLB values of 10.88, 11.82, and 12.59, respectively, 3D-
HLB (10.88, 5.45), (11.82, 4.18), (12.59, 2.35)), it was not
possible to determine CMC values for 8PEG-15 to 10PEG-
15, due to the high hydrophobicity of the extended, ramified
hydrophobic tail.
sure
(tris(allyldimethylsiloxy))silane (0.78 g, 92.5% yield). 1H NMR (CDCl3,
500 MHz): d=5.78 (m, 3H; OSi(CH3)2CH2CHCH2), 4.86–4.91 (m, 6H;
OSi(CH3)2CH2CHCH2), 3.23 (t, J=7.5 Hz, 2H; O3SiCH2CH2CH2N3),
1.61–1.66 (m, 2H; O3SiCH2CH2CH2N3), 1.59 (d, J=10.0 Hz, 6H; OSi-
(CH3)2CH2CHCH2), 0.50–0.57 (m, 2H; O3SiCH2CH2CH2N3), 0.12 ppm (s,
(without
heating)
to
yield
3-azidopropyl-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
18H; OSiACHTUNGTRNEUNG
(CH3)2CH2CHCH2); 13C NMR (CDCl3 125 MHz): d=134.13,
113.79, 54.07, 26.24, 23.29, 11.61, À0.19 ppm; 29Si NMR (CDCl3, 99 MHz,
1% w/v Cr
(acac)3): d=4.92 (M), À67.21 (T) ppm. LRMS (ES+): m/z:
calcd for [M+K]+: 496.94; found: 496.3.
Conclusion
Synthesis of 7PEG-15: Propiolic acid (4.2 g, 60.0 mmol), toluene
(90 mL), and
a catalytic amount of p-toluenesulfonic acid (0.5 g,
Taken together, all these results clearly show that this new
class of hyperbranched, explicit silicone–ethylene oxide am-
phiphiles is extremely efficient surfactants. The methodology
developed herein combines two extremely efficient coupling
reactions that should allow the synthesis of tailor-made sur-
factants, at the wish of the experimentalist. This versatility
allows for extensive tuning of surfactant morphology (alkyl
versus silicone, degree of branching, size of the hydrophobic
moiety), which leads to a great control over the aggregation
properties and thus to a wide range of potential applications
as detergents, oil-in-water or water-in-oil stabilizers, and so
forth.
2.6 mmol) was successively added in a round-bottomed flask containing
monomethoxy poly(ethylene oxide) (av mol wt: 750, 15.0 g, 20.0 mmol).
The flask, equipped with a Dean Stark apparatus, was heated with azeo-
tropic removal of water. Completion of the reaction was monitored by
1H NMR spectroscopy, by comparison of the three protons of the termi-
nal methoxy with the appearance of the methylenic ester protons at
4.32 ppm (about 20 h). The solution was then cooled to room tempera-
ture, and washed three times with an aqueous potassium carbonate solu-
tion (50 mL). The organic phase was then dried over magnesium sulfate,
concentrated in vacuo, and the crude product directly loaded onto a
chromatography column packed with silica gel. Elution started with pure
dichloromethane, then increasing amounts of methanol were added to
the eluent (up to 5% v:v). The fractions containing the propiolate ester
were combined, evaporated under reduced pressure to afford pure mo-
nopropiolate, monomethoxy-terminated poly(ethylene oxide) (12.1 g,
1
À
77% yield). H NMR (CDCl3, 600 MHz): d=4.34 (t, J=6.0 Hz, 2H;
À
À
À
COOCH2 ), 3.74 to 3.55 (m, ꢀ60H; OCH2CH2O ), 3.37 (s, 3H;
OCH3), 2.89 (s, broad, 1H; HCCCOO); 13C NMR (CDCl3, 125 MHz):
d=152.68, 75.67, 74.56, 71.94, 70.57, 68.57, 65.24, 59.03. HRMS (ES+):
m/z: calcd for [M+NH4]+: 806.4749; found: 806.4768.
Experimental Section
Representative procedures for the synthesis of each type of building
block used, explicit iodopropyl-modified silicones, the corresponding
azido derivatives, monopropiolate-terminated poly(oxyethylene)s, and
the surfactants prepared by metal-free click ligation, are given above.
Detailed experimental procedures and spectroscopic characterizations of
all synthesized compounds are provided in the Supporting Information.
Synthesis of 12PEG-15:
Synthesis of 3-iodopropylACTHNUTRGNE(UNG tris(allyldimethylsiloxy))silane: Allyldimethyl-
silane (1.55 g, 15.5 mmol) was added to a solution of iodopropyltrime-
thoxysilane (1.00 g, 3.4 mmol) in dry hexane (10 mL). The mixture was
stirred at room temperature for 5 min before the addition of tris(penta-
fluorophenyl)borane (40 mL of a 0.078m solution in toluene, 3.1 mmol).
After a short induction time (about 100 s), rapid evolution of gas and
heat from the solution occurred. The mixture was allowed to cool to
room temperature before the addition of neutral alumina to remove B-
Prepared propiolate-terminated monomethoxy poly(ethylene oxide)
(0.500 g, 0.63 mmol; av mol wt 750, mass calculated by HRMS
788.47 gmolÀ1) and dry toluene (ca. 1 mL) was added to a 5 mL round
bottom flask equipped with a magnetic stir bar and previously prepared
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
azidopropylACTHNUTRGNE(UNG tris(allyldimethylsiloxy))silane (0.37 g, 0.82 mmol). The mix-
AHCTUNGTRENNUNG
ture was then stirred at 458C and monitored by NMR spectroscopy for
completion (typical time required is 64 h). The mixture was then concen-
trated in vacuo, and the crude product directly loaded onto a chromatog-
raphy column packed with silica gel. Elution started with pure dichloro-
methane, then increasing amounts of methanol were added to the eluent
(up to 3% v:v). The fractions containing the desired compound were
then evaporated under reduced pressure to affording pure pale yellow
12PEG-15 as two isomers, with a ratio of roughly 1:4. (0.712 g, 90.2%
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
18H; OSiACHTUNGTRENNUNG
(CH3)2CH2CHCH2); 13C NMR (CDCl3 125 MHz): d=134.15,
113.82, 28.29, 26.25, 16.18, 10.99, À0.16 ppm; 29Si NMR (CDCl3, 99 MHz,
1% w/v Cr
(acac)3): d=4.92 (M), À68.01 (T) ppm. HRMS (ES+): m/z:
calcd for [M+Na]+: 565.0919; found: 565.0917.
Synthesis of 3-azidopropyl(tris(allyldimethylsiloxy))silane (5-N3): A solu-
tion of 3-iodopropyl(tris(allyldimethyl-siloxy))silane (1.00 g, 1.8 mmol) in
AHCTUNGTRENNUNG
1
yield). Major isomer 1,4 (ca. 75%): H NMR (CDCl3, 600 MHz): d=8.05
ACHTUNGTRENNUNG
(s, 1H; g), 5.73–5.78 (m, 3H; j), 4.82–4.88 (m, 6H; k), 4.50 (t, J=6.0 Hz,
2H; d), 4.36 (t, J=7.8 Hz, 2H; c), 3.79 (t, J=6.0 Hz, 2H; e), 3.59–3.68
anhydrous DMF (2 mL) was added to a 10 mL round-bottomed flask
equipped with a magnetic stir bar. Sodium azide (0.24 g, 3.7 mmol) was
added, and the mixture was stirred at room temperature. The reaction
was monitored by 1H NMR spectroscopy; once full substitution of the
iodo group was achieved (reaction was completed within 24 h), water
(20 mL) was added. The desired product was then extracted with hexanes
(25 mL), and the water phase extracted again with hexanes (3ꢁ10 mL).
The organic layers were combined and dried over sodium sulfate (10 g).
À
À
(m, ꢀ60H; OCH2CH2O ), 3.48–3.53 (m, 2H; f), 3.36 (s, 3H; OCH3),
1.92–1.96 (m, 2H; b), 1.56 (d, J=12 Hz, 6H; i), 0.43–0.47 (m, 2H; a),
0.09 ppm (s, 18H; h); 13C NMR (CDCl3 150 MHz): d=160.82, 139.90,
138.22, 133.95, 127.45, 113.93, 72.07, 70.70, 69.08, 64.23, 59.15, 53.08,
26.16, 24.80, 11.34, À0.17 ppm; 29Si NMR (CDCl3, 119 MHz, 1% w/v Cr-
(acac)3): d=5.80 (M), À67.63 (T). HRMS (ES+): m/z: calcd for [M+
1540
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Chem. Eur. J. 2012, 18, 1536 – 1541

Silicone Surfactants
FULL PAPER
NH4]+: 1263.6818; found: 1263.6854; HLB value=20ꢁ(719.925/
1245.79)=11.55. Minor Isomer 1,5 (ca. 25%): 1H NMR (CDCl3,
600 MHz): d=8.15 (s, 1H; g’), 5.73–5.78 (m, 3H; j), 4.82–4.88 (m, 6H;
k), 4.67 (t, J=9.0 Hz, 2H; c’), 4.44 (t, J=6.0 Hz, 2H; d’), 3.72 (t, J=
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À
À
6.0 Hz, 2H; e’), 3.59–3.68 (m, ꢀ24H; OCH2CH2O ), 3.48–3.53 (m, 2H;
f), 3.36 (s, 3H; OCH3), 1.89–1.91 (m, 2H; b’), 1.53 (d, J=12.0 Hz, 6H;
i’), 0.43–0.47 (m, 2H; a), 0.07 ppm (s, 18H; h’); 13C NMR (CDCl3
150 MHz): d=158.49, 139.90, 138.22, 127.45, 134.09, 113.77, 72.07, 70.70,
68.88, 64.70, 59.15, 52.87, 26.16, 24.71, 11.34, À0.23 ppm; 29Si NMR
(CDCl3, 119 MHz, 1% w/v Cr
N
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Acknowledgements
We thank the Natural Sciences and Engineering Research Council of
Canada for financial support of this work.
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Published online: December 27, 2011
Chem. Eur. J. 2012, 18, 1536 – 1541
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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