Synthesis of alkoxysilyl substituted cyclophosphazenes and their properties in the sol-gel process

Article abstract of DOI:10.1007/PL00010178

Cyclophosphazenes with different alkoxysilyl substituents were synthesized as new starting compounds for material synthesis via the sol-gel process. Their hydrolysis was investigated by FT Raman spectroscopy, and the thermal stability of the hydrolyzed and condensed new cyclophosphazenes was determined via thermogravimetric analysis. The organopolysiloxane of the type (N = P(CH₂SiO_3/2)₂)₅ is thermally stable up to 430°C in air. Cyclophosphazenes bearing 3-aminopropyltriethoxysilane (APTES) substituents were cocondensed with methacryloxypropyltrimethoxysilane, and some properties of coatings obtained from this composition were compared with the properties of a coating made from a mixture of tetraethoxysilane (TEOS) and methacryloxypropyltrimethoxysilane.

Full text of DOI:10.1007/PL00010178

Monatshefte fuÈr Chemie 130, 89±98 (1999)
Synthesis of Alkoxysilyl Substituted
Cyclophosphazenes and their Properties
in the Sol-Gel Process
Ã
Andreas Schneider, Stefan Kairies, and Klaus Rose
Fraunhofer Institute for Silicate Research, D-97082 WuÈrzburg, Germany
Summary. Cyclophosphazenes with different alkoxysilyl substituents were synthesized as new
starting compounds for material synthesis via the sol-gel process. Their hydrolysis was investigated
by FT Raman spectroscopy, and the thermal stability of the hydrolyzed and condensed new
cyclophosphazenes was determined via thermogravimetric analysis. The organopolysiloxane of the
type (N ˆ P(CH2SiO3/2)2)5 is thermally stable up to 430ꢀC in air. Cyclophosphazenes bearing
3-aminopropyltriethoxysilane (APTES) substituents were cocondensed with methacryloxypropyl-
trimethoxysilane, and some properties of coatings obtained from this composition were compared
with the properties of a coating made from a mixture of tetraethoxysilane (TEOS) and
methacryloxypropyltrimethoxysilane.
Keywords. Alkoxysilyl substituted cyclophosphazenes; Hydrolysis; Thermal stability; Coatings.
Synthese von alkoxysilylsubstituierten Cyclophosphazenen und ihre Eigenschaften
im Sol-Gel-Prozeû
Zusammenfassung. Cyclophosphazene mit unterschiedlichen Alkoxysilylsubstituenten wurden als
neue Ausgangsverbindungen fuÈr die Materialsynthese im Sol-Gel-Prozeû hergestellt. An den neuen
Cyclophosphazenverbindungen wurde die Hydrolysereaktion mittels FT-Raman-Spektroskopie
È
untersucht. Die thermische Stabilitat der hydrolysierten und kondensierten Cyclophosphazene
wurde mittels Thermogravimetrie bestimmt. Das Polysiloxan mit der Zusammensetzung
ist an Luft bis 430ꢀC stabil. Cyclophosphazene mit 3-Aminopropyltriethoxy-
(N ˆ P(CH2SiO3/2 25
)
silan (APTES) als Substituent wurden mit Methacryloxypropyltrimethoxysilan kokondensiert. Die
aus dem resultierenden Sol hergestellten Schichten wurden mit Schichten aus Tetraethoxysilan
(TEOS) und Methacryloxypropyltrimethoxysilan verglichen.
Introduction
During the last years, sol-gel derived coatings have been well established for
various applications. The sol-gel route, originally directed towards the synthesis of
purely inorganic materials, is increasingly being extended to the preparation of
inorganic/organic copolymers [1]. Starting from hydrolyzable molecular com-
Ã
Corresponding author

90
K. Rose et al.
pounds e.g. RSi(OEt)3, formation of a siloxane network is induced by reaction with
water. Polymerizable or special functional groups R in¯uence the chemical and
physical properties of the resulting materials to a high degree [2]. In order to
increase the ®eld of applications for this type of material, new compositions are
investigated world-wide with the aim to improve and tailor the desired material
properties. Since the sol-gel process requires monomeric hydrolyzable alkoxysilyl
compounds, new alkoxysilyl substituted cyclophosphazenes were synthesized with
the goal to incorporate these thermally stable ring systems into organically
modi®ed polysiloxanes via sol-gel processing [3].
Results and Discussion
Synthesis of the precursor molecules
The incorporation of cyclophospazenes into organopolysiloxanes via sol-gel
processing affords the synthesis of monomeric hydrolyzable alkoxysilyl substituted
cyclophosphazenes as precursor molecules. The easiest way to introduce an
alkoxysilyl group is the reaction between hexachlorocylotriphosphazene and
3-aminopropyltriethoxysilane (APTES). According to a general procedure devel-
oped by Allcock for the synthesis of aminosubstituted cyclophosphazenes [4],
3-aminopropyltriethoxysilane was reacted with hexachlorocyclotriphosphazene in
toluene.
Scheme 1
This reaction provided 1 in 82% yield. In an analogous reaction using 6
equivalents of butylamine in the ®rst step and 3 equivalents of 3-aminopropyl-
triethoxysilane as well as an excess of triethylamine in the second step, compound
2 was isolated as a mixture of geminal and non-geminal isomers.
Scheme 2
Van den Grampel et al. introduced allylaryl substituents into cyclotriphos-
phazene for the purpose of hydrosilylation [5]. Following this route, three chlorine
atoms in hexachlorocyclotriphosphazene were substituted by potassium-2-meth-
oxy-4-allylphenolate, leading to the non-geminal product 3. In the second step, the
remaining chlorine atoms were replaced by a stoichiometric amount of sodium
phenolate. Compound 4 was isolated in a yield of 49% calculated from the amount

Alkoxysilyl Substituted Cyclophosphazenes
91
of hexachlorocyclotriphosphazene used. The substitution of all chlorine atoms is
necessary due to the instability of the phosphorus-chlorine bond towards
hydrolysis.
Scheme 3
Hydrosilylation of 4 with triethoxysilane under catalysis of [H2PtCl6]/2-
propanol in THF ®nally afforded the silylated compound 5 in 78% yield.
Scheme 4
In order to obtain cyclophosphazenes containing a direct phosphorus-carbon
linkage without nitrogen or oxygen as heteroatom in the bridging unit between the
phosphazene ring and the alkoxysilyl moiety, a different approach was necessary.
The cyclophosphazene ring is formed by a thermal decomposition reaction of
(H3C)2BrP=NSi(CH3)3. A modi®cation of the pyrolysis reaction of the N-silyl-P-
bromophosphinimine established by Neilson et al. [6] leads to decamethylcyclo-
pentaphosphazene in a yield of 84%.
Complete or partial lithiation of decamethylcyclopentaphosphazene followed
by the addition of chlorotrimethoxysilane results in the formation of the silylated
compounds 6 and 7.
Scheme 5

92
K. Rose et al.
FT Raman spectroscopic investigations
Raman spectroscopy has proven to be a powerful tool for the investigation of the
sol-gel process [7]. Raman data provide information about the hydrolysis reaction
of the alkoxysilanes leading to the silsesquioxane network. In Fig. 1, the Raman
spectra of 1 during the reaction with water are shown. After starting the hydrolysis
using a stoichiometric amount of water with respect to the number of hydrolyzable
1
alkoxysilyl groups and NH4F as catalyst, the band at 650 cm diminishes. This
band can be assigned to the ꢀ(SiO3) stretchting vibration of the Si(OEt)3 moiety
[7] and shows the decrease of the unhydrolyzed compound 1 during formation of
1
the siloxane network. The band at 884 cm
assigned to the CO-stretching
vibration of ethanol [8] appears during the reaction indicating the evolving of
ethanol due to hydrolysis of 1.
For the evaluation of the reaction kinetics, the intensities of the Raman bands at
1
1
650 cm and 884 cm were determined and plotted against the reaction time
(Fig. 2).
Generally, the decrease of the ꢀ(SiO3) stretchting vibration goes along with the
increase of the CO-stretching of ethanol as expected. The curves show that the
decrease of the Si(OEt)3 moiety is complete after 120 min, whereas EtOH
formation is nearly ®nished after about 200 min. This phenomenon is explained by
the formation of partially hydrolyzed intermediate species (RSi(OH)(OEt)2 and
RSi(OH)2OEt) which could not be identi®ed due to their low intensities in this
Raman experiment, but which also eliberate ethanol.
It turned out that the hydrolysis of 1 depends strongly on the catalyst used. As
can be seen from Fig. 3, only NH4F is signi®cantly effective. The same behaviour
is observed for 2. Therefore, NH4F is used as a catalyst in the following
experiments with 1 and 2.
Fig. 1. Raman spectra of 1 during hydrolysis at 20ꢀC with 0.1 M NH4F as catalyst; the characteristic
Raman bands are indicated in the plot; the plots are recorded 0 min (solid), 50 min (dashed), and
500 min (dotted) after start of the hydrolysis reaction

Alkoxysilyl Substituted Cyclophosphazenes
93
Fig. 2. Kinetic plot of the hydrolysis of 1; the curve indicated by squares represents the evolving of
ethanol, the curve indicated by crosses represents the decrease of unhydrolyzed 1
Fig. 3. Kinetic plot of EtOH formation from 1 (®lled squares: catalysis with 0.1 M HCl, circles:
0.1 M NEt3, triangles: 0.1 M NaOH, un®lled squares 0.1 M NH4F)
A completely different behaviour was observed with 6 and 7. The hydrolysis
rate is four times faster than for 1 and 2 and independent from the catalyst used. In
the present case, even the reaction without any catalyst proceeds in the same time
as the catalyzed reaction. The effect is shown for 6 in Fig. 4. This behaviour is

94
K. Rose et al.
Fig. 4. Kinetic plot of EtOH formation from 6 (®lled squares: 0.1 M HCl catalysis, circle: without
catalysis, triangles: 0.1 M NaOH catalysis, un®lled squares: 0.1 M NH4F catalysis)
partly attributed to the more reactive methoxy groups. It is also possible that a
neighbouring group mechanism is operating and that the nitrogen atoms of the
phosphazene ring act as a donor and a pentavalent intermediate is formed that
stretches and weakens the Si±OMe bonds.
Thermal stability of cyclophosphazene modified organopolysiloxanes
The samples obtained from the hydrolysis experiments were dried for two hours at
120ꢀC in an oven and submitted to TGA. The decomposition temperature
measured in air was de®ned as the temperature where a weight loss of 5% had
occurred [9]. The hydrolysis products derived from 1 and 2 are fairly instable and
start to decompose around 220ꢀC. Both the stabilizing in¯uence of the phenyl
group and the presence of an oxygen link to the phosphazene ring in the siloxane
derivative of 5 increase signi®cantly the stability up to 320ꢀC. The highest thermal
stability was measured for the hydrolysis products of 6 and 7 which exhibit
decomposition temperatures of 345ꢀC and 430ꢀC, respectively. On the one hand,
the direct P±C-linkage in 6 and 7 increases the stability of the resulting
phosphazene siloxanes compared to derivatives with an oxygen or a nitrogen as
bridging atom. On the other hand, the higher number of alkoxysilyl groups in 7
compared to 6 faciliates inorganic silicate-like crosslinking also leading to a higher
thermal stability.
Coating properties
An important feature of the polysiloxane coating materials developed at the
Fraunhofer Institute for Silicate Research known as ORMOCER1s (Trademark of

Alkoxysilyl Substituted Cyclophosphazenes
95
È
the Fraunhofer-Gesellschaft zur Forderung der angewandten Forschung e.V.) is
their hardness. Therefore, they are widely used as scratch resistant coatings on
various substrates [10, 11]. In order to elucidate the properties of polysiloxanes
containing cyclophosphazenes, the new alkoxysilanes 1 and 2 were cocondensed
with methacryloxy-propyltrimethoxysilane (MEMO). The obtained sols were
applied on glass and polycarbonate substrates and cured by UV induced
polymerization of the methacrylic group using Irgacure 5001 as photoinitiator.
The resulting coatings were compared to a UV cured coating derived from
tetraethoxysilane (TEOS) and MEMO. In preliminary investigations it turned out
that the hardness of the coatings prepared from 1 (MEMO:1 ˆ 16:0.9) and 2
(MEMO:2 ˆ 16:1.8) was 256 N/mm2 and 276 N/mm2, respectively. Layers
prepared from MEMO and TEOS (ratio:16:4) exhibit only 208 N/mm2. This
signi®cant increase of hardness is remarkable since the amount of hydrolyzable
and crosslinkable alkoxy groups in the sols derived from TEOS, 1 and 2 were
equal. The higher hardness of the layers made from 1 and 2 can be attributed to the
higher degree of three-dimensional inorganic crosslinking of the large silyl
substituted cyclophosphazene. The higher hardness of the layer derived from 2
compared to that from 1 can be explained by the increased steric hindrance in 1
which possesses 18 alkoxy groups. This high steric hindrance will interfere with
the hydrolysis reaction and on a larger scale with the condensation reaction. Thus,
the formation of the silicate-like network is limited. This assumption is manifested
by solid state 29Si NMR experiments. The 29Si CP/MAS spectra of the hydrolysis
and condensation products derived from 1 show a smaller intensity of the T3-peak
than the spectra of the product derived from 2. Therefore, the inorganic
crosslinking in products derived from 2 is higher than in products derived from 1.
Experimental
1H, 13C, and 31P NMR spectra were recorded using a Bruker AMX 400 NMR spectrometer. Solid
state 29Si NMR spectra were obtained a Bruker DSX 400 instrument. IR spectra were measured
using a Nicolet FTIR spectrometer Magna 750. Raman spectra were recorded in a tempered Raman
cell attached to a Bruker RFS100 Raman spectrometer. Mass spectra were performed on a Finnigan
MAT 8200. All reactions for the synthesis of phosphazene monomers were carried out under an
atmosphere of dry argon in oven dried glassware. Hydrolysis reactions were conducted in ambient
atmosphere. To the synthesized polysiloxanes 1% (w/w) Irgacure 5001 (Ciba Geigy) was added, and
the coatings solutions were applicated via knife coating on a glass or polycarbonate substrate and UV
cured within 20 seconds. The universal hardness was determined by microindentation with a
Fischerscope H100.
(NP[NHCH2CH2CH2Si(OEt)3]2)3 (1; C54H132N9O18P3Si6)
6.64 g (30 mmol) 3-aminopropyltriethoxysilane were added dropwise at 0ꢀC to a solution of 1.78 g
(5.0 mmol) hexachlorocyclotriphosphazene and 3.34 g (33 mmol) triethylamine in 100 ml toluene.
After the addition, the reaction mixture was heated to re¯ux for 24 h. Filtration under argon followed
by solvent removal left 5.97 g (82%) 1 as colourless viscous liquid.
1H NMR (CDCl3, ꢁ, 400 MHz): 0.73 (t, CH2Si, 12H), 1.14 (t, OCH2CH3, 54H), 1.75 (m,
CH2CH2CH2, 12H), 3.07 (t, NCH2, 12H), 3.75 (q, OCH2CH3, 36H) ppm; 13C NMR (CDCl3, ꢁ,
100 MHz): 8.09 (CH2Si), 18.5 (OCH2CH3), 26.6 (CH2CH2CH2), 44.7 (NCH2, 12H), 58.4

96
K. Rose et al.
(OCH2CH3) ppm; 31P NMR (CDCl3, ꢁ, 162 MHz): 17.9 ppm; IR (Film): ꢀ ˆ 1183±1195 cm
1
(P=N).
(NP[NHCH2CH2CH2Si(OEt3)][NHCH2CH2 CH2CH3])3 (2; C39H96N9O9P3Si3)
6.32 g (86.4 mmol) n-butylamine were added dropwise at 0ꢀC to a solution of 5.0 g (14.4 mmol)
hexachlorocyclotriphosphazene in 100 ml toluene. After the addition, the reaction mixture was
heated to re¯ux for 24 h. The solution was decanted from the precipitate. 9.56 g (43.2 mmol)
3-aminopropyltriethoxysilane were added to the obtained solution. The resulting mixture was
re¯uxed for 30 h. Filtration under argon followed by solvent removal left 12.7 g (82%) 2 as a mixture
of isomers. 2 was a colourless highly viscous liquid.
1H NMR (CDCl3, ꢁ, 400 MHz): 0.73 (t, CH2Si, 6H), 0.93 (t, CH2CH2CH2CH3, 9H), 1.14
(t, OCH2CH3, 27H), 1.63 (m, CH2CH2CH2CH3, 6H), 1.71 (m, CH2CH2CH2CH3, 6H), 1.75
(m, CH2CH2CH2, 6H), 3.07 (t, NCH2, 5H), 3.11±3.19 (m, ((NHCH2)(NHCH2CH2CH2CH3)), 12H),
3.26 (t, NHCH2CH2CH2CH3), 3.75 (q, OCH2CH3, 18H) ppm; 13C NMR (CDCl3, ꢁ, 100 MHz): 8.09
(CH2Si), 10.2 (CH2CH2CH2CH3), 18.9 (OCH2CH3), 22.5 (CH2CH2CH2CH3), 25.7
(CH2CH2CH2CH3), 26.6 (CH2CH2CH2), 44.7 (NCH2), 58.4 (OCH2CH3) ppm; 31P NMR (CDCl3,
ꢁ, 162 MHz): 14.2 (d, P(NHBu)2, JPNP ˆ 22 Hz), 16.3 (dd, P(NHBu)(AMEO), JPNP ˆ 17 Hz, 22 Hz),
1
18.4 (dd, P((AMEO)2, JPNP ˆ 17 Hz, 22 Hz) ppm; IR (Film): ꢀ ˆ 1192±1196 cm (P=N).
(NP[O(C6H3)(OMe)CH2CHCH3]Cl)3 (3; C30H33Cl3N3O6P3)
A solution prepared from 9.85 g (60 mmol) 4-allyl-2-methoxyphenol and 1.44 g (60 mmol) sodium
hydride in 100 ml THF was added dropwise at 0ꢀC to 6.96 g (20.0 mmol) hexachlorocyclotriphos-
phazene in 60 ml THF. The reaction mixture was stirred for 12 h at 20ꢀC and subsequently heated to
re¯ux for 4 h. The solvent was removed in vacuo. The obtained liquid was dissolved in 50 ml
diethylether, washed with water, dried over Na2SO4, and the solvent was removed in vacuo. Traces
of 4-allyl-2-methoxyphenol were removed at 120ꢀC (0.4 mbar), and 10.1 g (13.8 mmol) of 3 was
isolated as a slightly yellow solid.
1H NMR (CDCl3, ꢁ, 400 MHz): 3.36 (d, ArCH2, 6H), 3.87 (s, OCH3, 9H), 5.11 (m, ˆ CH2, 6H),
5.85 (m, CH2CHCH2, 3H), 7.03 (m, ArH, 9H) ppm; 31P NMR (CDCl3, ꢁ, 162 MHz): 13.3
1
(P(OAr)(Cl)) ppm; IR (CCl4): ꢀ ˆ 1235±1242 (P=N) cm
.
(NP[O(C6H3)(OMe)CH2CHCH2]OPh)3 (4; C45H42N3O6P3)
A solution prepared from 3.78 g (40.2 mmol) phenol and 0.96 g (40.2 mmol) sodium hydride in 50 ml
THF was added to a solution of 8.60 g 3 in 50 ml THF. The mixture was heated to re¯ux for 24 h.
THF was removed in vacuo. 30 ml water and 1 ml 0.1 M HCl were added to the crude product. The
aqueous solution was extracted with CHCl3. The combined organic layers were dried over Na2SO4,
and the solvent was removed in vacuo. The liquid was dissolved in 20 ml pentane and puri®ed via
¯ash chromatography (silica gel 50, 30±70 mesh, petroleum 40±60:ethylacetate ˆ 4:1). After
evaporation of the solvent in vacuo, 7.74 g (71%) of 4 were obtained as a colourless viscous liquid.
1H NMR (CDCl3, ꢁ, 400 MHz): 3.34 (d, ArCH2, 6H), 4.97 (m, ˆ CH2, 6H), 5.72 (m,
CH2CHCH2, 3H), 7.22±7.28 (m, ArH, 27H) ppm; 31P NMR (CDCl3, ꢁ, 162 MHz): 8.82
1
(P(OAr)(OPh)) ppm; IR (CCl4): ꢀ~ ˆ 1235±1242, 1254±1272 (P=N) cm
.
(NP[O(C6H3)(OMe)CH2CH2CH2Si(OEt)3]OPh)3 (5; C63H90N3O15Si3)
4.53 g (5.00 mmol) 4 were dissolved in 15 ml THF and 0.5 ml of a 10 6 M solution of H2PtCl6 in
2-propanol were added. After stirrig for 1 h at 20ꢀC, 2.4 g (15.0 mmol) triethoxysilane were added

Alkoxysilyl Substituted Cyclophosphazenes
97
and heated to re¯ux for 24 h. Volatile substances were removed in vacuo. The crude yellow product
was dispersed in 30 ml heptane and ®ltered over a 3 cm layer of silica gel 60. The ®ltrate was
concentrated to provide 5.45 g (78%) 5 as a colourless liquid.
1H NMR (CDCl3, ꢁ, 400 MHz): 0.59 (t, CH2Si, 6H), 1.13 (t, OCH2CH3, 27H), 1.53 (m,
CH2CH2CH2, 6H), 3.32 (t, ArCH2, 6H), 3.81 (q, OCH2CH3, 18H), 3.89 (s, OCH3, 9H) 7.22±7.28 (m,
ArH, 24H) ppm; 31P NMR (CDCl3, ꢁ, 162 MHz): 8.93 (P(OAr)(OPh)) ppm; IR (CCl4): ꢀ~ ˆ 1235±
1
1242, 1262±1274 (P=N) cm
.
[NP(CH3)2]5 (C10H30N5P5)
32.7 g (143 mmol) P-bromo-P,P-dimethyl-N-silylphosphinimine were heated for 2 h to 160ꢀC in a
round bottom ¯ask equipped with a re¯ux condenser and a liquid separator. The trimethylbromo-
silane formed during the reaction was continuously removed via the liquid seperator. To complete
the reaction, the temperature was slowly rised to 200ꢀC. After 5 h the reaction was completed.
Sublimation of the obtained white needles yielded 9.02 g (84%) [NP(CH3)2]5.
3
1H NMR (CDCl3, ꢁ, 400 MHz): 1.45 (P(CH3)2, JPH ˆ 12 Hz) ppm; 31P NMR (CDCl3, ꢁ,
‡
‡
162 MHz): 19.25 (P(CH3)2) ppm; El-MS: m/z ˆ 375.3 (M , 19%), 360.1 (M -CH3, 57%), 300.0
‡
‡
‡
(M -NP(CH3)2, 58%), 285.1 (M -NP(CH3)2-CH3, 100%), 225.1 (M -2 NP(CH3)2, 5%), 210.1
‡
(M -2 NP(CH3)2-CH3, 57%).
(NP[CH3][CH2Si(OMe)3])5 (6; C25H70N5O15P5Si5)
40 ml of a 2 M solution of n-BuLi in heptane were added dropwise to an ice-cooled solution of
3.00 g (8.00 mmol) decamethylcyclopentaphosphazene in 80 ml THF. After stirring for 12 h, this
reaction mixture was added to a vigorously stirred solution of 8.50 g (42.0 mmol) chlorotrimethoxy-
silane in 100 ml THF at a temperature of 78ꢀC. The mixture was warmed up to room temperature,
stirred for a period of 12 h, and then ®ltered. The solvent and unreacted chlorotrimethoxysilane were
removed in vacuo. The crude product was dissolved in 80 ml dichloromethane and ®ltered over a
2 cm layer of silica gel 60. After evaporation of the solvent, 11.5 g (72%) 6 were obtained as a
colourless viscous liquid.
1H NMR (CDCl3, ꢁ, 400 MHz): 0.96 (s, PCH3, 21H), 1.27 (br, PCH2Si, 6H), 3.38 (s, OCH3, 18H)
ppm; 13C NMR (CDCl3, ꢁ, 100 MHz): 6.31 (PCH3) 9.09 (CH2Si), 56.2 (OCH3) ppm; 31P NMR
1
(CDCl3, ꢁ, 162 MHz): 25.2 (PCH3CH2Si) ppm; IR (KBr): ꢀ~ ˆ 1187 (P=N) cm
.
(NP[CH2Si(OMe)3]2)5 (7; C40H105N5O30P5Si10)
7 was prepared analogous to 6 but using twofold amounts of n-BuLi and chlorotrimethyoxysilane.
1
Yield: 72%; H NMR (CDCl3, ꢁ, 400 MHz) 1.42 (br, PCH2Si, 20H), 3.23 (s, OCH3, 90H) ppm;
13C NMR (CDCl3, ꢁ, 100 MHz): 9.09 (CH2Si), 56.2 (OCH3)ppm; 31P NMR (CDCl3, ꢁ, 162 MHz):
1
25.2 (P(CH2Si)2) ppm; IR (KBr): ꢀ~ ˆ 1187 (P=N) cm
.
Hydrolysis experiments for Raman investigations
General procedure
If not mentioned otherwise, 1 g of the alkoxysilyl substituted cyclophosphazene was dissolved in 1 g
of solvent (ethylacetate or 2-propanol). A stoichiometric amount of water (calculated by the number
of alkoxy groups) or instead a 0.1 M or 1 M aqueous solution of a catalyst was added, and the mixture
was stirred in a cell inside the Raman spectrometer.

98
K. Rose et al.: Alkoxysilyl Substituted Cyclophosphazenes
Hydrolysis of 5
3.41 g (2.44 mmol) 5 were dissolved in 20 ml ethyl acetate; 0.40 g 0.1 M HCl were added, and the
mixture was stirred for 12 h at 20ꢀC.
Synthesis of the coating sols
Sol 1 prepared from MEMO and TEOS:
1.16 g (64.5 mmol) 0.1 M aqueous solution of NH4F were added to an ice-cooled solution of 4 g
(16.1 mmol) methacryloxypropyltrimethoxysilane (MEMO) and 0.84 g (4.03 mmol) TEOS in 14.4 g
ethyl acetate. After 10 min the ice-bath was removed and the mixture was stirred for another 2 h.
Sol 2 prepared from MEMO and 1:
1.16 g (64.5 mmol) 0.1 M aqueous solution of NH4F were added to an ice cooled solution of 4 g
(16.1 mmol) methacryloxypropyltrimethoxysilane (MEMO) and 1.30 g (0.89 mmol) 1 in 14.4 g ethyl
acetate. After 10 min the ice-bath was removed and the mixture was stirred for another 2 h.
Sol 3 prepared from MEMO and 2:
To an ice cooled of 4 g (16.1 mmol) methacryloxypropyltrimethoxysilane (MEMO) and 1.81 g
(1.79 mmol) 2 in 7.2 g ethyl acetate and 7.2 g ethanol, 1.16 g (64.5 mmol) 0.1 M aqueous solution of
NH4F were added. After 10 min the ice-bath was removed and the mixture was stirred for another
2 h.
Finally, photoinitiator was added to the sols, and the sols were applied on the substrates as
described above.
Acknowledgements
Financial support from the Deutsche Forschungsgemeinschaft is gratefully acknowledged.
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Received June 12, 1998. Accepted (revised) September 30, 1998