Fluorine-containing dialkoxysilanes. the formation of complexes with aminopropyltriethoxysilane and production of transparent films

Article abstract of DOI:10.1007/s11172-009-0130-3

Three dialkoxysilanes with fluorine-containing groups were synthesized: methyl(3, 3, 3-tri-fluoropropyl)dimethoxysilane, methyl(3, 3, 3-trifluoropropyl)bis(2, 2, 2-trifluoroethoxy)silane, and methyl(2, 2, 2-trifluoro-1-trifluoromethylethoxymethyl)bis(2, 2, 2-trifluoro-1-trifluoro- methylethoxy)silane. It was found by IR and 29Si NMR spectroscopies that (3-aminopropyl)-triethoxysilane forms complexes with the indicated compounds, which are hydrolyzed in the presence of air moisture to form films of high optical quality.

Full text of DOI:10.1007/s11172-009-0130-3

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 1015—1022, May, 2009
1015
Fluorineꢀcontaining dialkoxysilanes. The formation of complexes
with aminopropyltriethoxysilane and production of transparent films
E. Yu. Ladilina, T. S. Lyubova, V. V. Semenov, Yu. A. Kurskii, and O. V. Kuznetsova
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831 2) 627497. Eꢀmail: llena@iomc.ras.ru
Three dialkoxysilanes with fluorineꢀcontaining groups were synthesized: methyl(3,3,3ꢀtriꢀ
fluoropropyl)dimethoxysilane, methyl(3,3,3ꢀtrifluoropropyl)bis(2,2,2ꢀtrifluoroethoxy)silane,
and methyl(2,2,2ꢀtrifluoroꢀ1ꢀtrifluoromethylethoxymethyl)bis(2,2,2ꢀtrifluoroꢀ1ꢀtrifluoroꢀ
methylethoxy)silane. It was found by IR and 29Si NMR spectroscopies that (3ꢀaminopropyl)ꢀ
triethoxysilane forms complexes with the indicated compounds, which are hydrolyzed in the
presence of air moisture to form films of high optical quality.
Key words: organosilicon compounds, organofluorine compounds, aminopropyltriethoxyꢀ
silane, films, thermostability, IR spectroscopy, 29Si NMR spectroscopy.
Intensive search for new protective antireflecting
coatings for optical lenses, laser crystals, fiber optical
waveguides, and units of optical integral schemes is being
performed at present. Materials of this type should
possess high transparent and low absorption in a wide
wavelength interval. Organosilicon oligomers and polyꢀ
mers with 3,3,3ꢀtrifluoropropyl and other more branched
organofluorine substituents are actively used for the
production of the above materials.1 Such polymers
are synthesized from diorganyldichlorosilanes1 by the
multistage method. The method includes the hydrolysis
of dichlorosilane, formation of a mixture of cyclic and
linear siloxanes, isolation of cyclotrisiloxanes of the highest
activity,2 and polymerization or copolymerization of the
latter with vinylꢀcontaining organosilicon compounds.1,2
The oligomers formed with vinyl terminal groups interact
with oligoorganohydrosiloxanes in the presence of the
Spier catalyst on heating to form a polymer. Hybrid
silicones containing polyfluoroalkane fragments between
the silicon atoms are also used to obtain protecting coatꢀ
ings with high transmission and relatively low refractive
index (~1.4).3,4 To prepare such polymers, terminal
organosilicon substituents are introduced into the preꢀ
liminarily synthesized fluorineꢀcontaining diene by the
hydrosilylation reaction involving diorganochlorosilane.
Then the chlorine atoms are subjected to hydrolysis and
the silanols formed are used in homoꢀ and copolyꢀ
condensation reactions.3,4 The solꢀgel method5 is simpler
in use and provides polymer coatings in one stage due to
the hydrolysis of organylalkoxysilanes.
we synthesized three dialkoxysilanes with organofluorine
substituents, namely, methyl(3,3,3ꢀtrifluoropropyl)ꢀ
dimethoxysilane (1), methyl(3,3,3ꢀtrifluoropropyl)bisꢀ
(2,2,2ꢀtrifluoroethoxy)silane (2), and methyl(2,2,2ꢀtriꢀ
fluoroꢀ1ꢀtrifluoromethylethoxymethyl)bis(2,2,2ꢀtrifluoroꢀ
1ꢀtrifluoromethylethoxy)silane (3).
Compounds 1 and 2 were synthesized from methylꢀ
(3,3,3ꢀtrifluoropropyl)dichlorosilane and corresponding
alcohols. The reaction of (chloromethyl)methyldichloroꢀ
silane with sodium alkoxide was used for the synthesis of
alkoxysilane 3. Sodium alkoxide was prepared by the reꢀ
action of hexafluoroisopropyl alcohol with NaH in THF
(Scheme 1).
For the purpose of using in processes of hydrolytic
polycondensation and production of transparent films,
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 990—997, May, 2009.
1066ꢀ5285/09/5805ꢀ1015 © 2009 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Ladilina et al.
Scheme 1
based on alkoxysilanes 1—3. It is organosilicon amine
and, hence, can act as a nucleophile favoring the hydroꢀ
lysis and condensation reactions to occur. The quaternary
ammonium salt formed with the participation of APTES
should be soluble in alkoxysilane. In addition, APTES has
three hydrolyzed ethoxy groups at the silicon atom, due
to which it can provide spatial crossꢀlinking of the oligoꢀ
mers formed.
To check whether the amino group of APTES (its
basicity is somewhat lower than that of usual alkylamines)
can interact with the silicon atom of nonfluorinated
alkoxysilanes, we mixed APTES and methyltrimethoxyꢀ
silane in an equimolar ratio. The IR spectrum of this
mixture (Fig. 1, curve 2) contains only absorption bands
corresponding to the uncharged primary amino group NH2
(νN—H 3367, 3296 cm–1). Thus, the organosilicon amine
forms no complex with methyltrimethoxysilane. Neverꢀ
theless, in air a mixture of MeSi(OMe)3 with APTES
(1 : 1) is solidified for 2 h. In this case, the hydrolysis can
be favored by hydroxide ions formed upon the interaction
of a molecule of the primary organosilicon amine with
air moisture (RNH3+OH–) after the composition was
deposited on the support.
The hydrolysis of diorganyldialkoxysilanes without
catalysts affords a mixture of liquid products: linear oligoꢀ
and polysiloxanes and sixꢀtoꢀeightꢀmembered cyclic
compounds.6,7 The hydrolysis of alkoxysilanes catalyzed
by acids and bases3,8,9 occurs most rapidly and completely
to yield elastic polymers. To prepare solid transparent
coatings, triꢀ or tetrafunctional compounds capable of
spatial crossꢀlinking of siloxanes should be added to
compositions based on diorganodialkoxysilanes.
Organosilicon compounds with fluorinated alkoxy
groups are stable to hydrolysis in an acidic medium.6
Organic amines (nucleophilic or basic) can be the
catalysts of this process. The kinetics of hydrolysis of
organylalkoxyꢀ and organylchlorosilanes in the presence
of various nucleophiles was studied.10,11 It was shown that
the formation of a complex of the organosilicon comꢀ
pound with a nucleophile favors racemization. However,
the direct existence of an intermolecular complex was not
detected by spectral methods. There were studied only
the initial and final products as well as the kinetics of the
substitution reaction. Nevertheless, it was convincingly
proved that the intermediate formed by the interaction
with the nucleophile was more reactive toward water. It
was also mentioned12 that halides of the pentacoordinated
(due to intramolecular interaction) silicon atom are much
more reactive in substitution reactions.
We studied the effect of basic additives on the
hydrolysis of alkoxysilanes 1—3 followed by the condenꢀ
sation of formed silanols for the series of aliphatic amines:
secꢀbutylamine, cyclohexylamine, diethylamine, and
triethylamine. The mixing of compound 1 with secꢀBuNH2
in an equimolar ratio resulted in warming of the mixture
and formation of a finely dispersed white precipitate. Its
IR spectrum contains absorption bands in the region of
2800—2400 cm–1 and 1512 cm–1, which indicates that the
precipitate can be a quaternary ammonium salt. The forꢀ
mation of similar precipitates was also observed when
compounds 1—3 were mixed with other aliphatic amines.
We assumed that the precipitation occurs due to the forꢀ
mation of a complex of the organosilicon compound with
the nucleophile.
To obtain transparent polymers based on compounds
1—3, it is necessary for the complex to dissolve in
alkoxysilane. The finely dispersed precipitate formed at
the moment of mixing of organic amine with compound 1
turned out insoluble in an excess of the latter. (3ꢀAminoꢀ
propyl)triethoxysilane (APTES) seems to be very promisꢀ
ing for the use as the second component of compositions
In the IR spectra of equimolar mixtures of APTES
with each alkoxysilane 1—3, the absorption bands of
bending vibrations of the N—H bonds of organosilicon
amine are shifted to lower wave numbers by 15 cm–1
compared to individual APTES. The spectra also contain
absorption bands corresponding to stretching vibrations
of the N—H bonds in the fragment
(broad band
in the region 2670—2390 cm–1) (Fig. 1, curves 3—5).
Their relative intensity increases in the series of comꢀ
pounds 1 < 2 < 3, i.e., with the accumulation of electronꢀ
withdrawing fluorineꢀcontaining alkylꢀ and alkoxyl subꢀ
stituents at the silicon atom. Probably, this is due to
the value of the positive charge on the silicon atom. The
chemical shift of the signal of protons of the methyl group
bound to the silicon atom depends directly on the positive
charge value on this atom. A comparative analysis of the
1Н NMR spectra of compounds 1—3 and methyltriꢀ
methoxysilane MeSi(OMe)3 (Table 1) shows that with an
increase in the number of fluorine atoms in the substituꢀ
ents at the Si atom the signal of protons of the methyl group
bound to this atom undergoes the downfield shift. Thus,
in the series MeSi(OMe)3, CF3CH2CH2SiMe(OMe)2,
CF3CH2CH2SiMe(OCH2CF3)2, and (CF3)2CHOCH2Siꢀ
Me(OCH(CF3)2)2 the positive charge on the silicon atom
increases. Therefore, the strongest complex with APTES
should yield compound 3. This conclusion agrees well
with the observed highest relative intensity of the IR
absorption bands corresponding to stretching vibrations
of the N—H bonds in the complex formed by APTES
with compound 3.
The spectra of all three mixtures (see Fig. 1) also
exhibit absorption bands attributed to stretching vibraꢀ

Fluorineꢀcontaining dialkoxysilanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1017
T
Table 1. Chemical shifts in the 1H NMR spectra of the signal of
protons of the methyl group at the silicon atom for compounds
1—3 compared to MeSi(OMe)3
1
2
Compound
δ (CH3Si)
MeSi(OMe)3
0.12
0.15
0.30
0.55
3
CF3CH2CH2SiMe(OMe)2 (1)
CF3CH2CH2SiMe(OCH2CF3)2 (2)
(CF3)2CHOCH2SiMe(OCH(CF3)2)2 (3)
4
of the starting alkoxysilane is a little higher. Therefore,
compound 3 forms somewhat more stable complex with
APTES.
5
In both cases, these closely lying signals can be asꢀ
signed to the pentacoordinated silicon atom13,14 in the 1 :
1 complexes with different spatial arrangement of subꢀ
stituents.14
4000
3000
ν/cm–1
Fig. 1. IR spectra of APTES (1) and its equimolar mixtures with
MeSi(OMe)3 (2), CF3CH2CH2SiMe(OMe)2 (3), CF3CH2CH2ꢀ
SiMe(OCH2CF3)2 (4), and (CF3)2CHOCH2SiMe(OCHꢀ
(CF3)2)2 (5).
tions of the N—H bonds of the primary amine (3369 and
3301 cm–1). In this connection, we believe that the
system studied are equilibrated (Scheme 2).
In these complexes five substituents are arranged
in space as a trigonal bipyramid. Since four of them
are different, they can be arranged via two modes. In the
first case, the groups at the vertices of the bipyramid are
different, and two of three substituents in the plane of the
silicon atom are the same. In another case, the ligands in
the vertices of the bipyramid and all three substituents
occupying the equatorial plane are different. That is why,
the complexes become chiral.
Scheme 2
In this connection, it was mentioned in several publiꢀ
cations15,16 that coordination N→Si can be accompanied
R = CH CH CH Si(OEt)
3
2
2
2
R´ = CH (1), CH СF (2), CH(CF ) (3)
3
2
3
3 2
T
F
R = CH CF (1, 2), CH OCH(CF ) (3)
2
3
2
3 2
1
The IR spectra of mixtures of compound 3 with APTES
in various mole ratios 1 : 1, 2 : 1, and 1 : 2 are shown in
Fig. 2. An increase in the relative content of both APTES
and fluorineꢀcontaining organosilicon compound inꢀ
creases the relative intensity of the absorption bands
of stretching vibrations of the N—H bonds of coordiꢀ
nated amine, i.e., shifts the equilibrium toward complex
formation.
2
3
The reactions of alkoxysilanes 2 and 3 with APTES
were also studied by 29Si NMR spectroscopy. The spectra
of two mixtures (2 + APTES and 3 + APTES) exhibit
three signals: one signal from the organosilicon amine
(–45.8 ppm) and two signals of approximately equal
intensity (–9.9 and –10.7 ppm for a mixture with comꢀ
pound 2 and –16.5 and –17.5 ppm for a mixture with
compound 3). In the latter case, Δδ relative to the signal
4000
3000
ν/cm–1
Fig. 2. IR spectra of mixtures of compound 3 and APTES in the
mole ratios 1 : 1 (1), 2 : 1 (2), and 1 : 2 (3).

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Ladilina et al.
Table 2. Change in the chemical shifts of protons of compound 2
and APTES in the 1H NMR spectra (mole ratio 1 : 1, solvent
(CD3)2C=O)
Table 3. Change in the chemical shifts of the carbon atoms
in compound 2 and APTES in the 13С NMR spectra (mole ratio
1 : 1, solvent (CD3)2C=O)
Fragment
δ
Δ
Fragment
δ
Δ
before mixing
in mixture
before mixing
Compound 2
–4.6 s
in mixture
Compound 2
0.38 s
1.00 m
2.27 m
4.32 q
Si—Me
CH2Si
–0.1 br.s
–2.3 s
10.5 br.s
9.0 s
4.5
Si—Me
0.27 m
0.87 m
2.19 m
3.87 q
–0.11
–0.13
–0.08
–0.45
2.3
3.1
1.6
CH2Si
CF3CH2
CF3CH2O
7.4 s
CF3CH2CH2
CF3CH2CH2
CF3CH2O
28.5 q
129.8 q
126.4 q
62.8 q
29.0 m
129.8 q
127.2 q
61.6 q
0.5
0.0
0.8
–1.2
APTES
SiCH2
CH2CH2CH2
CH2N
0.58 m
1.48 m
2.59 t
0.60 m
1.69 m
3.24 t
0.02
0.21
0.65
CF3CH2O
APTES
NH2
1.73 br.s
1.84,
SiCH2
CH2CH2CH2
CH2N
9.8 s
25.8 s
55.4 s
9.9 s
25.7 s
55.4 s
58.6 s
59.8 s
19.7 s
0.1
–0.1
0.0
3.3
0.2
1.95 both br.s
3.81 q
1.19 t
OCH2CH3
OCH2CH3
3.79 q
1.18 t
0.02
0.01
OCH2CH3
OCH2CH3
59.6 s
19.6 s
by changes in the 1H NMR spectra when the substituents
at the nitrogen and silicon atoms become nonequivalent.
This is mainly detected only on cooling (from –40 to
–120 °С). However, there are examples when nonꢀ
equivalence of substituents at the nitrogen atom in the
1H NMR spectra appears at positive temperatures as
well (20—30 °С).17 In these cases, the silicon atom
should have two substituents with easily polarizable bonds
(Si—Cl, Si—Br, Si—OAc).
0.1
trum also indicates the formation of complexes of two
types (I and II) and a possibility of different (equatorial
and axial) arrangement of substituents at the silicon atom
when amine is coordinated to this atom. The broadening
of these signals can indicate the fast (in the NMR scale)
exchange of the axial and equatorial substituents between
complexes of different structures.14
The reaction of alkoxysilane 2 with APTES was also
studied by 1H and 13C NMR spectroscopy. As can be seen
from the data in Table 2, in the 1H NMR spectrum of an
equimolar mixture of the compounds the signals of proꢀ
tons of alkoxysilane undergo the upfield shift, which is
most substantial for the SiMe, CH2Si, and CF3CH2O
groups. At the same time, the signals from protons of the
trimethylene bridge of APTES undergo the downfield
shift, being is maximum for the CH2N group. The most
appreciable changes occur with the signal of protons bound
to the nitrogen atom. The spectrum of APTES contains
only one broad signal, whereas the spectrum of the equiꢀ
molar mixture of the compounds exhibits two signals of
the amino group with much smaller broadening. In the
13C NMR spectra the signals of both compounds exhibit
both the upfield and downfield shifts. It is especially
remarkable that we observe two separate signals of the CH2N
group in APTES (Table 3), two signals for the MeSi group,
and two signals for the CH2Si group of alkoxysilane 2.
As mentioned above, intermediates of this type are
more reactive toward nucleophilic reactants than the
initial organosilicon compounds.10—12,18 They facilitate
hydrolysis and condensation processes to occur and can
favor film formation under mild conditions.
Compositions formed of compounds 1—3 and APTES
are hydrolyzed by air moisture to form transparent smooth
sold glassy silicone films. The data on the influence of the
component ratio on the time of film solidification are
shown in Table 4. An increase in the relative content of
APTES in the mixture shortens the time of film solidificaꢀ
tion. This is related first to an increase in the threeꢀfuncꢀ
tional component providing spatial crossꢀlinking of
polysiloxane in the mixture. In addition, it is seen from
the data presented that the compositions based on comꢀ
pounds 2 and 3 are solidified much more slowly at any
ratios of components. Probably, this occurs because in the
intermediately formed complex the fluorinated ethoxy and
isopropoxy groups create considerable steric hindrances
for the attack of the nucleophilic reactant (H2O and
especially silanol). The methoxy substituents in compound
1 do not prevent the complex to interact with the nucleoꢀ
phile and, hence, the compositions based on compound 1
are solidified more rapidly.
1
These changes in the chemical shifts in the H and
13C NMR spectra can be related to the interaction of the
amino group of APTES with the Si atom of alkoxysilane,
which changes the charge on the nitrogen and silicon
atoms and, as a consequence, on the carbon atom and
protons of the groups directly bound to these atoms. The
doubling of signals of some groups in the 13C NMR specꢀ
Heating to 100 °С shortens the structurization time.
For instance, on heating the composition based on comꢀ

Fluorineꢀcontaining dialkoxysilanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1019
Table 4. Dependence of the solidification time for the composiꢀ
tions of compounds 1—3 and APTES on the component ratio
pound 1 and APTES in the mole ratio 9 : 1 gives the solid
film within 5 min.
The study of the transmission spectra of the films preꢀ
pared from compounds 1—3 showed that they had almost
no absorption in the region of 300—2800 nm. In the
spectra of the organosilicon coatings based on polyꢀ
dimethylsiloxanes the bands of component vibrations of
С—Н bonds are usually most intense (4500—4000 cm–1).19
As can be seen from Fig. 3, these absorption bands are
very lowꢀintensity.
Composition
Mole ratio
t*/min
1 + APTES
1 : 1
3 : 1
9 : 1
1 : 1
2 : 1
4 : 1
1 : 1
2 : 1
4 : 1
10
20
60
15
90
120
45
60
2 + APTES
3 + APTES
The IR spectra of the films prepared from the comꢀ
positions based on compounds 1—3 and APTES are presented
in Fig. 4. In each polymer organosilicon amine exists in both
the coordinated and free state. The absorption of unꢀ
bound amine (two very intense bands at 3440—3028 cm–1
(νN—H) and the mediumꢀintense band at 1602 cm–1
(δN—H)) is especially pronounced in the spectrum of the
film from compound 1 (Fig. 4, curve 1). Bending vibrations
120
* Time of solidification (t) of the components of the film.
T
a
of the N—H bonds in the
fragment at 1569 cm–1
are most intense in the spectrum of the film based on
compound 3 (Fig. 4, curve 3).
The content of the gel fraction for the polymers of the
compositions using alkoxysilanes 1, 2, and 3 are 44.2,
40.5, and 79.7%, respectively. The sol fractions are transꢀ
parent resinꢀlike substances with the molecular weight
∼1000. The IR spectra of the sol and gel fractions for each
polymer are nearly identical, which confirms the particiꢀ
pation of the organosilicon amine in the formation of
both the crossꢀlinked polysiloxane and lowerꢀmolecularꢀ
weight products.
The processes that occur on heating were studied for
the films formed of compounds 1—3 and APTES in the
mole ratio of 4 : 1.
In the IR spectrum of the film of the composition
based on alkoxysilane 2 all absorption bands become less
intense after each subsequent heating stage (100, 150, and
6000
5000
4000
3000
ν/cm–1
T
b
T
1
2
2
3
3
4000 3500 3000 2500 2000 1500 1000 ν/cm–1
6000
5000
4000
3000
ν/cm–1
Fig. 3. IR spectra of the films obtained from the compositions
2 + APTES in the mole ratio 4 : 1 (l = 15 μm) (a) and 3 + APTES
in the mole ratio 4 : 1 (l = 20 μm) (b).
Fig. 4. IR spectra of the films obtained at the mole ratio of the
components 4 : 1 from the compositions 1 + APTES (l = 15 μm)
(1), 2 + APTES (l = 15 μm) (2), and 3 + APTES (l = 20 μm) (3).

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Ladilina et al.
200 °С). The weight loss is 5, 19, and 25%, respectively.
The intensity of the absorption band at 1563 cm–1
decreases gradually in the IR spectrum of the film. The
intensity of the broadened absorption band at 1664 cm–1
simultaneously appears and gradually increases, and the
film gains a weak yellow shade. After thermal treatment
analogous changes occur with the film formed of the comꢀ
position based on alkoxysilane 1. However, after 200 °С
two lowꢀintensity absorption bands appear in its IR specꢀ
trum at 1659 and 1690 cm–1 and the film also becomes
yellow. The weight loss for the film differs substantially:
maximum losses occur at 100 °С (32%), they are less at
150 °С (11%), and the weight losses are still less at 200 оС
(9%). The appearance of a weak yellow color of the films
and simultaneously the appearance of lowꢀintensity
absorption bands at 1660—1670 cm–1 can be related to
the oxidation of methyl and methylene groups at the
silicon atom that occurs on heating in air. In this case,
carbonyl groups can be formed yielding imines if the
matrix contains amine. It is known20 that the absorption
bands of these fragments in individual pure compounds
are very intense. Since, they appear as weak in the specꢀ
trum of the films, we can conclude that the processes
resulting in their formation are insignificant.
The substantial decrease in all absorption bands in the
IR spectra of the films and considerable weight losses
indicate, possibly, the destruction of the polymer siloxane
chains to form volatile cyclic compounds, which are
easily removed on heating. The occurrence of these reacꢀ
tions is facilitated due to the presence of the catalyst
in the matrix.8 Lowꢀmolecularꢀweight components of the
sol fractions of the polymers can evaporate under these
conditions.
The film formed of compound 3 and APTES on heatꢀ
ing behaves differently. The IR spectrum contains two
absorption bands at 1569 and 1627 cm–1 corresponding
to bending vibrations of the N—H bonds of coordinated
and noncoordinated amine. Thermal treatment for 30 min
at 100 °С results in the insignificant (by 2%) increase in
the film weight. The former band disappears. Simultaꢀ
neously two new absorption bands appear. The first of
them (3402 cm–1, intense) corresponds to stretching
vibrations of the O—H bonds, and the second bond
(1754 cm–1, weak) corresponds, probably, to vibrations of
the carbonyl group. The relative intensity of the absorpꢀ
tion bands attributed to the alkoxy groups (899 and
687 cm–1) remains unchanged. After heating at 150 °С
(30 min) the film weight somewhat decreases (the loss is
only 7%), and its optical properties remain unchanged.
The IR spectrum exhibits an insignificant decrease in the
relative intensity of the absorption bands of the hydroxyꢀ
and fluorineꢀcontaining alkoxy groups at 3402, 899,
and 689 cm–1. Thermal treatment for 30 min at 200 °С
induces a light yellow color accompanied by substantial
changes in the IR spectrum. The absorption band of
stretching vibrations of the O—H bonds almost disapꢀ
pears, the intensity of the absorption bands attributed to
the NH2 and RFO groups decreases considerably, and the
broadened mediumꢀintensity absorption band appears
at 1667 cm–1
.
The observed spectral changes can be assigned to the
occurrence of the following processes. The compositions
contain APTES that forms a complex with siloxane and
also with hexafluoroisopropanol evolved during hydrolyꢀ
sis. On heating to 150 °С these quaternary ammonium
salts decompose, but the alcohol leaves the matrix only
at 200 °С, which is indicated by the substantial (27%)
weight loss of the film at this temperature. The methyl
and methylene groups at the silicon atom are oxidized to
the carbonyl fragments simultaneously with the described
process, and the carbonyl fragments interact with the
amine in the composition, resulting in the formation of
imines.
After heating to 150 °С a weak absorption band
appears at 310 nm in the UV spectrum of the film
deposited on the quartz support. The intensity of this
band increases considerably with the temperature raising
to 200 °С. This confirms the appearance of the fragments
containing the C=O and C=N bonds in the polymer.
It follows from the experiment performed that the film
based on compound 3 shows higher thermostability. Probꢀ
ably, this is related to the branched fluorinated substituꢀ
ents (CF3)2CHOCH2 at the silicon atoms in polysiloxane.
They can prevent both the penetration of air moisture
into deep layers of the polymer and polysiloxane decomꢀ
position to form volatiles due to the occurrence of
interchain exchange reactions.21
Thus, it was established by IR and NMR spectroscopies
that an additive of (3ꢀaminopropyl)triethoxysilane to
monomers 1—3 affords intermolecular complexes. Transꢀ
parent glassy films are formed from the compositions based
on alkoxysilanes 1—3 and APTES. It was shown that an
increase in the relative content of APTES in the studied
compositions and heating shorten the time of film solidiꢀ
fication. The sol films produced from compound 3 and
APTES have high thermal stability and do not lose their
optical properties on heating to 150 °С. At higher temꢀ
peratures (200 °С) the substituents at the silicon atom
in the polymer begin to oxidize and result in noticeable
changes in the polymer composition.
Experimental
The IR spectra of compounds and compositions as liquid
films or suspensions in Nujol between KBr plates and the
IR spectra of solid films formed on CaF2, NaCl, and KBr films
were recorded on an FSMꢀ1201 FTꢀIR spectrometer. The UV
transmission spectra of the films were measured on a Perkin
Elmer Lambdaꢀ25 spectrometer. NMR spectra were obtained
on a Bruker Avance DPXꢀ200 instrument (200 MHz for

Fluorineꢀcontaining dialkoxysilanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1021
1H nuclei, 50 MHz for 13C nuclei, and 39.7 MHz for 29Si nuclei)
at 25 °С using Me4Si as internal standard. The synthesized
compounds were analyzed on a Tsvetꢀ530 gas chromatograph
using a stainless steel column (0.3×200 cm, 5% SEꢀ30 on the
solid support Chromaton NꢀSuper). The sol fractions of the
polymer films were extracted with diethyl ether and analyzed on
a Knauer Smartline chromatograph with Phenogel Phenomenex
5u columns (300×7.8 mm) and a refractometric detector.
δ: –6.7 (s, SiCH3); 25.6 (s, CH2Si); 70.4 (m, CH(CF3)2); 122.3
1
(q, CF3, JC,F = 283.0 Hz). 29Si NMR ((СD3)2CO), δ: –5.1.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 08ꢀ03ꢀ00771
and 08ꢀ03ꢀ90024) and the Council on Grants at the
President of the Russian Federation (Program for State
Support of Leading Scientific Schools of the Russian
Federation, Grant NSh 1396.2008.3).
The mobile phase was THF with a flow rate of 2 mL min–1
.
Calibration was carried out using polystyrene standards with
molecular weights in the range from 3 420 to 2 570 000.
Elemental analyses were carried out at the Analytical Center
of the Institute of Organometallic Chemistry of the Russian
Academy of Sciences.
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20
yield of 10.40 g (54%), m.p. 27 °С (26 Torr), nD = 1.3610
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20
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Methyl(3,3,3ꢀtrifluoropropyl)bis(2,2,2ꢀtrifluoroethoxy)silane
(2). Compound 2 was synthesized similarly to compound 1
from 2,2,2ꢀtrifluoroethanol (12.73 g, 0.127 mol) and methylꢀ
(3,3,3ꢀtrifluoropropyl)dichlorosilane (12.09 g, 0.057 mol).
Compound 2 was obtained after distillation under reduced
pressure in a yield of 12.60 g (65%), m.p. 60 °С (22 Torr),
20
nD = 1.3302. Found (%): С, 27.99; Н, 3.89. С8Н11О2SiF9.
Calculated (%): С, 28.40; Н, 3.30. IR, ν/cm–1: 2958, 2806,
1449, 1373 (С—Н), 1269, 1169 (C—F), 1072 (Si—O—C), 905,
856 (OCH2CF3). 1Н NMR (CDCl3), δ: 0.30 (s, 3 Н, SiCH3);
0.93 (m, 2 Н, CH2Si); 2.12 (m, 2 Н, CH2CF3); 4.05 (q, 4Н,
ОСН2CF3). 13С NMR ((СD3)2CO), δ: –4.6 (s, SiCH3); 7.4
2
(s, CH2Si); 28.5 (q, CH2CH2CF3, JC,F = 30.5 Hz); 62.8 (q,
OCH2CF3, 2JC,F = 36.1 Hz); 126.4 (q, OCH2CF3, 1JC,F = 277.5 Hz);
129.8 (q, CH2CH2CF3, 1JC,F = 275.5 Hz). 29Si NMR ((СD3)2CO),
δ: –0.04.
Methyl(2,2,2ꢀtrifluoroꢀ1ꢀtrifluoromethylethoxymethyl)bisꢀ
(2,2,2ꢀtrifluoroꢀ1ꢀtrifluoromethylethoxy)silane (3). Chloromethylꢀ
methyldichlorosilane (3.36 g, 0.021 mol) was added dropwise
with stirring in an argon flow to sodium hexafluoroisopropylate
obtained from hexafluoroisopropyl alcohol (10.36 g, 0.062 mol)
and sodium hydride (1.48 g, 0.062 mol) in THF. The reaction
mixture was heated for 0.5 h at 50—60 °С. The precipitate was
separated on the Schott filter and washed with hexane. The
residue was distilled under reduced pressure. Compound 3
17. R. J. P. Corriu, G. Royo, A. Saxce, J. Chem. Soc., Chem.
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was isolated in a yield of 5.10 g (45%), b.p. 58 °С (20 Torr),
20
nD = 1.3232. Found (%): С, 23.60; Н, 2.14. С11Н8О3SiF18
.
Calculated (%): С, 23.25; Н, 1.60, IR, ν/cm–1 : 2948, 2889,
1376 (С—Н), 1293, 1230, 1220 (C—F), 1200 (C—F; C—O—C),
1105, 1050 (Si—O—C), 894 (OCH(CF3)2). 1Н NMR (CDCl3),
δ: 0.55 (s, 3Н, CH3); 2.94 (s, 2 H, CH2Si); 3.96 (m, 1 Н,
CH(CF3)2); 4.64 (m, 2 H, OCH(CF3)2). 13С NMR ((СD3)2CO),
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Eds R. G. Jones, W. Ando, J. Chojnowski, Kluwer, Dodrecht,
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Received July 2, 2008;
in revised form November 17, 2008