A versatile synthetic route to phosphonate-functional monomers, oligomers, silanes, and hybrid nanoparticles

Article abstract of DOI:10.1021/ma047526e

The highly selective single Michael addition of diethyl vinylphosphonate to alkylamines represents a very versatile synthetic route affording a large variety of novel multifunctional phosphonates including aminoalkylphosphonates, phosphonate functional silanes, and phosphonate-functionalized acrylic monomers. The hydrolysis of the phosphonate group results in a phosphonic acid functional monomer which can be used as component of dental composites exhibiting improved filler - matrix interaction. The sol - gel reaction of the phosphonate- functional silanes produced novel phosphonate-functional organic/ inorganic hybrid nanoparticles with particle sizes ranging from 30 to 100 nm.

Full text of DOI:10.1021/ma047526e

9548
Macromolecules 2005, 38, 9548-9555
A Versatile Synthetic Route to Phosphonate-Functional Monomers,
Oligomers, Silanes, and Hybrid Nanoparticles
Martin Schmider,*,† Ekkehard Mu1 h,† Joachim E. Klee,‡ and Rolf Mu1 lhaupt†
Institut fu¨r Makromolekulare Chemie und Freiburger Materialforschungszentrum der
Albert-Ludwigs-Universita¨t, Stefan-Meier-Strasse 31, D-79104 Freiburg im Breisgau, Germany, and
Dentsply DeTrey GmbH, De-Trey-Strasse 1, D-78467 Konstanz, Germany
Received December 1, 2004; Revised Manuscript Received August 20, 2005
ABSTRACT: The highly selective single Michael addition of diethyl vinylphosphonate to alkylamines
represents a very versatile synthetic route affording a large variety of novel multifunctional phosphonates
including aminoalkylphosphonates, phosphonate functional silanes, and phosphonate-functionalized acrylic
monomers. The hydrolysis of the phosphonate group results in a phosphonic acid functional monomer
which can be used as component of dental composites exhibiting improved filler-matrix interaction. The
sol-gel reaction of the phosphonate-functional silanes produced novel phosphonate-functional organic/
inorganic hybrid nanoparticles with particle sizes ranging from 30 to 100 nm.
Introduction
phosphonate-functional acrylics, silanes, and organic/
inorganic hybrid nanoparticles. This expanded molec-
ular tool box is based upon the Michael addition of
diethyl vinylphosphonate to various amines including
aminoalkylsilanes. Special emphasis is being placed
upon the syntheses and characterization of novel phos-
phonate intermediates in one-pot reactions. Moreover,
the multifunctional phosphonate silanes were used in
dual cure reactions, combining sol/gel condensation with
free radical polymerization, to prepare nanocomposites.
Both phosphonate-functional intermediates and phos-
phonate-functional nanoparticles were examined as new
interfacial coupling agents in dental composites.
Dimethacrylates are widely used for matrixes of
dental materials in conjunction with photoinitiators,
silane interfacial coupling agents, and functionalized
silica fillers.1-4 The properties of such composite materi-
als are greatly influenced by both the filler dispersion
and the interfacial adhesion of the dispersed inorganic
filler. Dispersion problems are frequently encountered
when using nanometer-scaled filler particles due to their
very strong interparticle interactions. An important
objective in dental chemistry is to combine properties
of polymers and ceramics by preparing organic/inorganic
hybrid systems via sol/gel chemistry. Sol/gel chemistry
is the key to preparing inorganic particles with variable
surface functionality including core/shell-type particles.5
In preferred compositions, micro- and nanometer-scaled
particles are attached to the acrylic organic matrix via
covalent or ionic bond formation, respectively.6 The
covalent interfacial coupling is achieved when acrylic
silanes are copolymerized. New families of acrylic nano-
composites with improved matrix/filler adhesion were
prepared from sol/gel reactions of bismethacrylate
silanes.7-10 As displayed in Scheme 1, the bismethacry-
late silanes are obtained when ethylene glycol acrylate
methacrylate (EGAMA) is reacted with aminoalkylsi-
lanes. Below room temperature, the acrylate group
reacts selectively with the primary amines. Exclusive
2-fold Michael addition accounts for the formation of
bismethacrylate silanes. In this molecular tool box
approach, the structures of the amines can be varied
over a very wide range. Although covalent interfacial
coupling is very effective, the ionomer coupling also
offers attractive potential. According to a recent study,
the incorporation of phosphonic acids into the acrylic
monomer promotes both biocompatibility and adhesion
of the dental materials to the teeth because calcium
phosphonates and phosphonate complexes are formed.11,12
However, most of the state-of-the-art acrylic phospho-
nates require tedious multistep syntheses.13-15 Here we
report an expanded molecular tool box approach toward
Results and Discussion
A. Monomers. A novel class of phosphonate-func-
tional acrylic monomers were prepared according to the
general synthetic route shown in Scheme 2. Key feature
of the synthesis of phosphonate monomers (1a-c) was
the Michael addition of a variety of primary amines to
the vinyl group of diethyl vinylphosphonate. For all
monomers, the conversion of the vinyl group in the
course of the Michael addition was monitored by 1H and
13C NMR spectroscopy. The addition reaction was com-
monly complete after 24 h at 70 °C, as evidenced by the
disappearance of the 1H NMR signals of the vinyl group
at 6.19, 6.04, and 5.97 ppm as well as the 13C NMR
signals at 135.3 and 126.1 ppm. At the same time
characteristic signals appeared at 1.94 and 2.85 ppm
in the 1H NMR spectra and at 27.0 and 42.1 ppm in the
13C NMR spectra, respectively, which can be assigned
to the new aliphatic bond. In 13C NMR, the character-
istic doublet shifts from 126.1 to 27.0 ppm due to the
hetero-coupling between the C-nucleus and the P-
nucleus. NMR spectroscopy provides evidence that in
the case of the addition product 1b the alkoxysilane
groups were not affected during Michael addition. In
contrast to the 2-fold Michael addition of acrylate
groups, exclusive monoaddition was observed for the
vinylphosphonate addition to the amines displayed in
Table 1. The GC-MS spectra of addition products 1a
and 1b typically show the expected molecular ions
[MH+] at m/z 272 (1a) and 386 (1b), in accord with the
formation of monoaddition product. Besides GC-MS,
† Institut fu¨r Makromolekulare Chemie und Freiburger Mate-
rialforschungszentrum der Albert-Ludwigs-Universita¨t.
‡ Dentsply DeTrey GmbH.
10.1021/ma047526e CCC: $30.25 © 2005 American Chemical Society
Published on Web 10/13/2005

Macromolecules, Vol. 38, No. 23, 2005
Phosphonate-Functional Compounds 9549
Scheme 1. Synthesis of Bismethacrylatesilanes via 2-Fold Michael Addition
Scheme 2. Synthesis of Phosphonate-Functional Monomers
also MALDI-TOF measurements confirmed the exclu-
measurements confirmed the formation of the expected
monomers 2a,b. The FAB-MS spectra show molecular
ions [MH+] at m/z 456 (2a) and 570 (2b), confirming
the formation of addition products with EGAMA. This
is shown in Figure 3 by the FAB-MS spectrum of the
monomer 2b.
sive formation of monoaddition product by reaction of
bis(aminopropyl)-terminated oligo(propylene oxide) (Jef-
famine) with diethyl vinylphosphonate (Figure 1). The
maxima of the signals in the MALDI-TOF spectrum
of 1c were shifted to higher m/z compared to the
maxima of the signals in the spectrum of Jeffamine
(Figure 2). The difference corresponds exactly to the
2-fold molecular weight of diethyl vinylphosphonate, i.e.,
monoaddition of every amine group of the oligomer with
diethyl vinylphosphonate has occurred.
The novel R,â-unsaturated amides 3a,b were pre-
pared according to a procedure published by Rodriguez
The monomers 2a,b were prepared by selective
Michael addition of 1a respectively 1b to the acrylate
functionalities of 2-(acryloyloxy)ethyl methacrylate.
2-(acryloyloxy)ethyl methacrylate was prepared accord-
ing to a procedure published by Moszner et al.16 The
1
rate of the reaction was monitored by H NMR spec-
troscopy. During the Michael addition, the signals of the
acrylate group at 6.5, 6.1, and 5.8 ppm decreased.
Typical new signals occurred at 2.6 and 2.2 ppm, which
are due to the new aliphatic bond. The same phenom-
enon was observed by 13C NMR spectroscopy. During
the Michael addition, the signals of the acrylate group
at 131 and 128 ppm shifted to 50 and 32 ppm in the
spectra. Besides 1H NMR, 13C NMR and FAB-MS
Figure 1. MALDI-TOF spectrum of 1c.

9550 Schmider et al.
Macromolecules, Vol. 38, No. 23, 2005
Table 1. Monomers 1a-c, 2a-b, and 3a-b Prepared via
Michael Addition and Amidation
Figure 3. FAB-MS spectrum of monomer 2b.
2a was observed at δ ) 31.1 ppm whereas in the
phosphonic acid 4 the resonance was found at δ ) 19.2
ppm.
B. Nanoparticles. The new phosphonate-function-
alized acrylic silanes can be condensed to form silicate
nanoparticles with reactive acrylate and phosphonate
surfaces. First the sol-gel condensation of phosphonate-
functionalized acrylic silane 2b was carried in the
presence of 3 wt % aqueous HF solution and ethyl
acetate as solvent. After stirring for 2 days at room
temperature, volatile components such as ethyl acetate
and water were removed under vacuum. Condensation
product of 2b (CP2b) was mixed with Bis-GMA/TGDMA
and then polymerized by free radical polymerization in
order to covalently attach the particles to the matrix.
After the resulting composite was milled, the obtained
nanocomposite powder was characterized by solid state
29Si cross-polarization magic angle spinning (CP MAS)
NMR spectroscopy. Figure 4 shows the spectrum of
CP2b. Formation of the silica network was evidenced by
the dominant NMR signal at -67.1 ppm, corresponding
to the Si bonded through O atoms to three other Si (T3).
Signals in the range of -58, -50, and -42 ppm
corresponding to Si bonded to two (T2), only one (T1) or
even no further Si (T0) were not detected, confirming
the cross-linked structure. Furthermore, the condensa-
tion product CP2b was characterized by transmission
electron microscopy (TEM). Figure 5 shows the TEM
image of condensation product of 2b (CP2b). According
to the analysis of numerous TEM images, the particles
formed have diameters in the range of 30 to 100 nm.
1
et al.17 and characterized by NMR spectroscopy. In H
NMR, typical new signals corresponding to the methyl
groups next to the N-nucleus, previously observed at
2.52 and 2.81 ppm, were afterward shifted to 3.28 and
3.53 ppm (3a). The same phenomenon was observed for
monomer 3b. The signals were shifted from 2.81 and
3.68 ppm to 3.59 and 4.72 ppm. This is due to the
improved shielding of the nuclei after amidation. Fur-
thermore, the ethoxy-substituted alkoxysilane groups
of 3b remained uncondensed as evidenced by the
existence of the 1H NMR signals at 1.3 and 3.8 ppm as
well as the 13C NMR signals at 18.3 and 58.5 ppm. The
reaction of bromotrimethylsilane with the dialkylphos-
phonate 2a and the hydrolysis of the resultant silyl
phosphonate were carried out to prepare the Zwitteri-
onic aminoalkylphosphonic acid 4 under very mild
conditions (Scheme 3). The spectral properties of 4
strongly supported the hydrolysis of the dialkylphos-
phonate 2a. In particular the 31P NMR was most
informative, since the resonance due to the phosphonate
Figure 2. Zoom of MALDI-TOF spectra of unmodified Jeffamine (left) and 1c (right).

Macromolecules, Vol. 38, No. 23, 2005
Phosphonate-Functional Compounds 9551
Scheme 3. Reaction Scheme of the Hydrolysis of the Dialkylphosphonate 2a
In a second approach silicate nanoparticles were
formed by co-condensation of silane 2b with tetraethyl
orthosilicate (TEOS) in different ratios as shown in
Table 2. The condensation reactions were carried out
again in the presence of 3 wt % aqueous HF solution
and ethyl acetate as solvent. The morphology of the
samples was detected by means of TEM. Figure 5 shows
the TEM image of condensation product of 2b with
TEOS in ethyl acetate (CP2b-TEOS-3) containing hybride
nanoparticles with diameters ranging from 30 to 60 nm.
Figure 4. 29Si (CP MAS) NMR spectra of condensation products 2b (CP2b) and (CP2b-TEOS-2).
Figure 5. TEM images of the nanoparticle dispersions CP2b and CP2b-TEOS-3.
Table 2. Mechanical Properties of Condensation Products CP2b-TEOS-x and Bis-GMA/TGDMA
2b/TEOS
[mol/mol]
SiOR/H2O
[mol/mol]
SiOR/H+
[mol/mol]
compressive
strength [MPa]
flexural
strength [MPa]
condensation product
Bis-GMA/TGDMA (70/30 w/w)
CP2b-TEOS-1
235 ( 12
110 ( 18
140 ( 20
140 ( 21
160 ( 26
60 ( 4
6 ( 2
7 ( 3
9 ( 5
12 ( 3
4.0
1.8
1.1
0.7
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
CP2b-TEOS-2
CP2b-TEOS-3
CP2b-TEOS-4

9552 Schmider et al.
Macromolecules, Vol. 38, No. 23, 2005
Figure 6. Fracture surface of the composite FC-MS-0.
Table 3. Mechanical Properties of Composites without Monomer 4 (FC-MS-0) and with Monomer 4 (FC-MS-1 and
FC-MS-5)
composite
Bis-GMA/TGDMA (70/30)
FC-MS-0
FC-MS-1
FC-MS-5
monomer 4 [wt %]
0
0
1
5
Bis-GMA/TGDMA (70/30) [wt %]
filler content [wt %]
100
80
79
75
0
2,6
238 ( 12
60 ( 4
1620 ( 50
96 ( 2
20
3,1
240 ( 11
62 ( 4
1850 ( 50
110 ( 2
20
3,3
235 ( 22
72 ( 6
2180 ( 80
115 ( 3
20
4,1
225 ( 14
69 ( 4
2010 ( 120
114 ( 1
viscosity η (23 °C) [Pa‚s]
compressive strength [MPa]
flexural strength [MPa]
Young’s modulus [MPa]
yield stress [MPa]
After removing volatile components, condensation prod-
ucts CP2b-TEOS-x were mixed with Bis-GMA/TGDMA
and polymerized by means of radicals in order to
incorporate the particles in the matrix. Bis-GMA pro-
vides the necessary hardness to mill the resulting
composites. The characterization of the obtained nano-
composite powders by means of solid state 29Si cross-
polarization magic angle spinning (CP MAS) NMR
spectroscopy led to the spectrum illustrated in Figure
4, evidencing the high alkoxysilane conversion. The
strongest signal at -66.1 ppm results from Si connected
through O atoms to three other Si (T3). Another two
signals were detected in the range of -100 (Q3) and
-110 ppm (Q4), supporting the cross-linked structure
of the nanoparticles.
addition 20 wt % glass filler (Potters Ballotini, micro-
spheres 5000CP-00, average diameter 5 µm, containing
7 wt % calcium ions and 2 wt % magnesium ions) and
different amounts of monomer 4 (0-5 wt %) to the
matrix resin consisting of Bis-GMA/TGDMA (weight
ratio 70:30 w/w). The uncured blend exhibits viscosities
in the range 3.1-4.1 Pa‚s, whereas the viscosities of the
resins increased by adding increasing amounts mono-
mer 4. After photopolymerization the fractured surfaces
of the composites (FC-MS-0, FC-MS-1, FC-MS-5, Table
3) were investigated by means of the environmental
scanning electron microscopy (ESEM) to obtain infor-
mation about the morphology of the composites. As
expected, the composite FC-MS-0 exhibits a very smooth
surface reflecting the absence of matrix/filler interaction
(Figure 6). However, addition of monomer 4 to compos-
ites FC-MS-1 and FC-MS-5, respectively, resulted in
matrix/filler interaction. Figure 7 shows the ESEM
images of particles with polymer bound on the glass
surface. Improved surface adhesion is likely to result
from the complexation of calcium and magnesium ions
of the filler via the phosphonic acid of monomer 4.
Phosphorus-containing monomers with phosphonic acid
were used as dentin adhesives because they can form
complexes with the calcium ions in the inorganic
components of dentin.14,15,19-21
C. Composites. Nanocomposites were prepared by
blending Bis-GMA/TGDMA (70:30 w/w) with the con-
densation products CP2b-TEOS-1-CP2b-TEOS-4 (CP: Bis-
GMA/TGDMA ) 70:30) and 0.75 wt % of the initiator
system campherchinone/dimethylaminobenzoic acid eth-
yl ester (1:1 mol/mol). After photopolymerization, the
mechanical data were examined (cf. Table 2). The
compressive strength of the nanocomposites was in the
range of 110-160 MPa and the flexural strength was
in the range of 6-12 MPa, respectively. In comparison
with the Bis-GMA/TGDMA without filler both the
compressive strengths and the flexural strengths were
surprisingly low. Most likely, after storage of the
samples over a period of 24 in water, the polymerizates
of methacrylates tend to hydrolyze in water and the
exposure to water plasticized the materials to the degree
Viscosities and mechanical properties of the prepared
composites are summarized in Table 3. Except for
compressive strength, the mechanical properties of the
composites with monomer 4 such as flexural strength,
Young’s modulus and the Yield stress are increased.
This is in accord with results in the literature, that the
yield behavior of glass filled polymers was dependent
on the glass/polymer interfacial adhesion.22,23 The sub-
stantial improvement of interfacial adhesion is ac-
that the mechanical properties were effectively lowered.
18
To examine the role of 4 (Scheme 3) with respect to
matrix/filler interaction, composites were prepared by

Macromolecules, Vol. 38, No. 23, 2005
Phosphonate-Functional Compounds 9553
Scheme 5. Amine PA-BA (1a)
Scheme 6. Amine PA-APTES (1b)
Scheme 7. Amine PA-JA (1c)
Figure 7. Fracture surface of the composite FC-MS-5.
during 4 h. After the reaction was stirred overnight, the
precipitate was filtered off and washed twice with 25 mL of
toluene. Then the reaction mixture was extracted twice with
150 mL of water, 100 mL of 1 N HCl, and 100 mL of 1 N Na2-
HCO3 and dried over Na2SO4. Thereafter the toluene was
distilled off (32 mbar 40 °C) and 100 mg of BHT were added.
IR: 1726 cm-1 (s, CdO), 1638 cm-1 (m, CdC).
Scheme 4. Ethylene Glycol Acrylate Methacrylate
(EGAMA)
1H NMR: δ ) 6.42 (9a, d), 6.11 (1b, 8, m), 5.83 (9b, d), 5.57
(1a, s), 4.39 (5, 6, s), 1.93 (3, s).
13C NMR: δ ) 167.1 (4), 165.9 (7), 135.9 (2), 131.4 (9), 128.0
(8), 126.1 (1), 62.4 (6), 62.2(5), 18.3 (3).
companied by only small improvements of 10-15% of
flexural strength and 9-18% of Young’s modulus.
Surprisingly, the best mechanical properties are ob-
served with 1 wt % of monomer 4. A possible explana-
tion is the lower network formation in the composite
FC-MS-5 and the low solubility of ionic monomer 4 in
the matrix at 5 wt %. Residual monomer which was not
bound to the surface of the fillers can plasticize the
composite matrix.24, 25
D. Conclusions. Novel phosphonate-functional mono-
mers and silanes containing a methacrylic group were
synthesized via single Michael addition of alkylamines
to diethyl vinylphosphonate and subsequent condensa-
tion with (meth)acryloyl chloride and another Michael
addition to 2-(acryloyloxy)ethyl methacrylate, respec-
tively. Thereby, phosphonate-functional silanes are
interesting sol-gel precursors for the preparation of
hybrid materials like organic/inorganic hybrid nano-
particles. Furthermore, the hydrolysis of the phospho-
nate group results in a phosphonic acid functional
monomer which can be used as component of dental
composites exhibiting improved filler-matrix interac-
tion.
General Procedure for the Preparation of Secondary
Amines PA-X. To a solution of diethyl vinylphosphonate (11
mmol) in 5 mL of absolute ethanol, the appropriate amine (10
mmol) dissolved in 5 mL of absolute ethanol was added. After
the mixture was stirred for 24 h at 70 °C, colorless oils (1a
and 1b) or a solid (1c) were obtained by distillation of the
solvent and characterized by mass spectrometry, GC, 1H NMR,
and 13C NMR.
Amine PA-BA (1a) (Scheme 5). C13H22NO3P (271.30): m/z
(GC-MS) ) 372 [MH+]. RT (GC): 27.5 min.
1H NMR: δ ) 7.21-7.29 (m, aromatic H), 3.99-4.11 (m,
POCH2CH3), 3.77 (s, 2), 2.90 (td, 3), 1.92-2.03 (m, 4), 1.27 (t,
POCH2CH3).
13C NMR: δ ) 140.0 (1), 128.4 (aromatic C), 62.1 (POCH2-
CH3), 52.9 (2), 43,7 (3), 27.1 (d, 4), 17.0 (POCH2CH3). 31P
NMR: δ ) 31.8 (s).
Amine PA-APTES (1b) (Scheme 6). C15H36NO6PSi
(385.52): m/z (GC-MS) ) 386 [MH+]. RT (GC): 28.8 min;
1H NMR: δ ) 3.98-4.05 (m, POCH2CH3), 3.78 (q, SiOCH2-
CH3), 2.81 (td, 4), 2.52 (t, 3), 1.85-1.94 (m, 5), 1.40-1.61 (m,
2), 1.23 (t, SiOCH2CH3), 1.13 (t, POCH2CH3), 0.54 (t, 1).
13C NMR: δ ) 62.1 (POCH2CH3), 58.8 (SiOCH2CH3), 52.9
(3), 43.7 (4), 27.1 (d, 5), 23.8 (2), 18.9 (SiOCH2CH3), 17.0
(POCH2CH3), 8.5 (1). 31P NMR: δ ) 30.5 (s).
1
Amine PA-JA (1c) (Scheme 7). H NMR: δ ) 3.96-4.03
Experimental Section
(m, POCH2CH3), 3.56 (s, OCH2CH2O, OCH2CH2N), 2.69-2.91
(m, 2), 1.88 (td, 1), 1.24 (t, POCH2CH3).
(Aminopropyl)triethoxysilane, benzylamine, diethyl vi-
nylphosphonate (DEVPh), trimethylsilyl bromide, 2-hydroxy-
ethyl methacrylate (HEMA), acryloyl chloride, methacryloyl
chloride, campher quinone, ethyl-4-(dimethylamino)benzoate
(DMABE), and di-tert-butyl-p-cresole (BHT) were supplied by
Fluka,2,2-bis-[p-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]-
propane (Bis-GMA), triethylenglycoldimethacrylate (TGDMA)
by Ro¨hm, triethylamine by Aldrich, Spheriglas 5000CP-00
(spherical diameter 5 µm) by Potters-Ballotini, and Jeffamine
ED 2003 (PEO II) Mn ≈ 1900 by Huntsman.
13C NMR: δ ) 70.4 (OCH2), 62.1 (POCH2CH3), 52.3 (NCH2),
40.5 (2), 26.8 (d, 1), 17.1 (POCH2CH3). 31P NMR: δ ) 29.4 (s).
General Procedure for the Preparation of the Hybrid
Monomers MA-PA-BA and MA-PA-APTES. Ethylene glycol
acrylate methacrylate (EGAMA) (10 mmol) was added slowly
to a solution of the appropriate amine (10 mmol) in 10 mL of
absolute ethanol. The mixture was stirred at 25 °C for 2 h.
Then the ethanol was distilled of and the mixture was stirred
for a further 48 h at 23 °C.
Hybrid Monomer MA-PA-BA (2a) (Scheme 8). C22H34-
Synthesis of 2-(acryloyloxy)ethyl methacrylate
(Scheme 4). In a three-necked flask equipped with stirrer,
thermometer and dropping funnel 89.88 g (0.691 mol) HEMA
and 76.88 g (0.760 mol) triethylamine were dissolved in 500
mL of absolute toluene. Under cooling (0-5 °C) 68.75 g (0.760
mol), acryloyl chloride dissolved in 50 mL of toluene was added
NO7P (455.49), m/z (FAB-MS) ) 456 [MH+].
1H NMR: δ ) 7.17-7.24 (m, aromatic H), 6.09, 5.48 (d, 11),
4.21 (s, 8, 9), 3.90-3.99 (POCH2CH3), 3.73 (s, 2), 2.84 (td, 3),
2.71 (t, 5), 2.40 (t, 6), 1,90-2.10 (m, 4), 1.82 (s, 12), 1.16 (t,
POCH2CH3).

9554 Schmider et al.
Macromolecules, Vol. 38, No. 23, 2005
Scheme 8. Hybrid Monomer MA-PA-BA (2a)
Scheme 11. Hybrid Monomer MAA-PA-APTES (3b)
Scheme 12. Hybrid Monomer MA-Phosphonic
Acid-BA (4)
Scheme 9. Hybrid Monomer MA-PA-APTES (2b)
chromatography of the residue on Al2O3 (MeOH:CHCl3 ) 1:1)
yielded the desired amide.
1
C24H48NO10PSi (454.09). H NMR: δ ) 5.03 (d, 8), 4.05-
4.09 (m, POCH2CH3), 3.76 (q, SiOCH2CH3), 3.45-3.60 (m, 4),
3.28 (t, 3), 1.95-2.15 (m, 5), 1.90 (s, 9), 1.50-1.70 (m, 2), 1.31
(t, SiOCH2CH3), 1.17 (t, POCH2CH3), 0.48 (t, 1).
Scheme 10. Hybrid Monomer MAA-PA-BA (3a)
13C NMR: δ ) 172.7 (6), 140.9 (7), 114.8 (8), 61.9 (POCH2-
CH3), 58.5 (SiOCH2CH3), 51.8 (3), 39.7 (4), 24.1 (d, 5), 22.7
(6), 20.6 (9), 18.3 (SiOCH2CH3), 16.5 (POCH2CH3), 7.6 (1). 31
NMR: δ ) 31.8 (s).
P
Hybrid Monomer MA-Phosphonic Acid-BA (4)
(Scheme 12). Trimethylsilyl bromide (3.062 g, 20 mmol) was
added slowly to a solution of 3 (4.104 g, 9 mmol) in 20 mL of
absolute dichlormethane. After being stirred under reflux for
1.5 h, excess trimethylsilyl bromide and the solvent were
removed by rotary evaporation. The residue was then dissolved
in 20 mL of methanol, and a white crystalline product
precipitated after stirring for 48 h.
13C NMR: δ ) 171.8 (7), 166.6 (10), 140.0 (1), 135.5 (13),
128.4 (aromatic C), 125.6 (11), 62.2 (POCH2CH3), 61.9 (9), 61.7
(8), 52.9 (2), 48.4 (5), 43.7 (3), 32.2 (6) 27.1 (d, 4), 18.0 (12),
17.0 (POCH2CH3).
31P NMR: δ ) 31.1 (s).
1
Hybrid Monomer MA-PA-APTES (2b) (Scheme 9).
C24H48NO10PSi (569.71), m/z (FAB-MS) ) 570 [MH+].
1H NMR: δ ) 6.03, 5.45 (d, 14), 4.17 (s, 9, 10), 3.84-4.00
(m, POCH2CH3), 3.64 (q, SiOCH2CH3), 2.55-2.68 (m, 4, 6),
2.20-2.36 (m, 3, 7), 1.77 (s, 12), 1,66-1.82 (m, 5), 1.29-1.42
(m, 2), 1.15 (t, SiOCH2CH3), 1.04 (t, POCH2CH3), 0.40 (t, 1).
13C NMR: δ ) 171.8 (8), 166.6 (11), 135.5 (13), 125.6 (14),
62.1 (POCH2CH3), 61.9 (10), 61.7 (9), 57.9 (SiOCH2CH3), 55.7
(3), 52.9 (2), 48.4 (6), 43.7 (3), 32.2 (7) 27.1 (4), 22.8 (d, 5), 20.0
(2), 18.0 (12), 17.9 (SiOCH2CH3), 16.6 (POCH2CH3), 7.4 (1);
31P NMR: δ ) 32.8 (s). 29Si NMR: δ ) -44.6.
C18H26NO7P (399.38). H NMR (D2O): δ ) 7.17-7.24 (m,
aromatic H), 5.88, 5.40 (d, 11), 4.21 (s, 8, 9), 3.73 (s, 2), 2.84
(3), 2,71 (t, 5), 2,40 (t, 6), 1.90-2.10 (m, 4), 1,74 (s, 12).
13C NMR (D2O): δ ) 171,8 (7), 166.6 (10), 140.0 (1), 135.5
(13), 128,4 (aromatic C), 125.6 (11), 61.9 (9), 61.7 (8), 52.9 (2),
48.4 (5), 43.7 (3), 32.2 (6) 27.1 (d, 4), 18.0 (12).
31P NMR (D2O): δ ) 19.2 (s).
Sol-Gel Condensation of MA-PA-APTES (2b) in ethyl
acetate (CP2b). 2b (2.00 g, 3.5 mmol) and ethyl acetate (7.80
g) were mixed. Initiation of the sol-gel condensation was
achieved by adding this mixture to a solution of aqueous HF
(3%) (0.195 g, 10.5 mmol H2O). After the mixture was stirred
for 2 days at ambient temperature, volatile components were
removed under vacuum for 1 h.
Sol-Gel Condensation of MA-PA-APTES (2b) with
TEOS (CP2b-TEOS-x). The hybrid monomer MA-PA-APTES
(5.50 g, 0.010 mol) and TEOS (0.5 g, 0.002 mol) were mixed
with a solution of aqueous HF (3%) (0.716 g, 0.039 mol H2O)
in ethyl acetate (3.284 g, 0.037 mol) to start the condensation
reaction of alkoxysilane groups. Three moles of water per mole
of alkoxysilane provided rapid condensation reactions. The
reaction mixture was stirred at room temperature for 2 days
to obtain full condensation.
Preparation of the Composites. Polymerizable matrix
resins were prepared by mixing Bis-GMA/TGDMA (70:30) with
the condensation products CP2b-TEOS-x (CP2b-TEOS-x: Bis-
GMA/TGDMA ) 70:30) and 0.75 wt % of the initiator system
campherchinone/dimethylaminobenzoic acid ethyl ester. Fur-
ther polymerizable matrix resins were prepared by mixing Bis-
GMA/TGDMA (70:30) with microspheres (average particle
size: 5 µm, Potters Ballotini, 5000CP-00) and 4 (molar ratio:
Table 1). In this case campherchinone/dimethylaminobenzoic
acid ethyl ester (0.75 wt %) was also used as initiator system.
All mixtures were degassed at 200 mbar and 60 °C for 30 min
and homogenized by stirring at room temperature for 1 h.
Preparation of the Test Specimens. Cylindrical test
specimens were made by placing the mixed polymerizable
matrix resins into stainless steel molds (height 6 mm, diameter
Hybrid Monomer MAA-PA-BA (3a) (Scheme 10). In a
three-necked flask equipped with stirrer, thermometer, and
dropping funnel PA-BA (3.732 g, 0.014 mol), triethylamine
(1.531 g, 0.015 mol) and DMAP (0.126 g, 0.001 mol) were
dissolved in 20 mL of dry dichlormethane. Under cooling (0-5
°C), methacryloyl chloride (1.582 g, 0.015 mol) dissolved in 10
mL of dry dichlormethane, was added during 1 h. After the
mixture was stirred overnight, the obtained precipitate was
filtered off and washed twice with 20 mL of dichlormethane.
Then the reaction mixture was extracted with 50 mL of water,
50 mL of 1 N HCl, and 50 mL of 1 N NaHCO3 and dried over
Na2SO4. Subsequently, dichlormethane was evaporated.
C
22H34NO7P (340.21). 1H NMR: δ ) 7.17-7.50 (m, aro-
matic H), 5.20 (d, 7), 4.70 (s, 2), 4.05-4.20 (m, POCH2CH3),
3.65 (td, 3), 1.95-2.20 (m, 4, 8), 1.30 (t, POCH2CH3).
13C NMR: δ ) 171.7 (5), 139.4 (1), 140.0 (1), 135.6 (6),
125.9-127.7 (aromatic C), 114.5 (7), 60.6 (POCH2CH3), 52.4
(3), 38.5 (2), 22.6 (d, 4), 19.5 (8), 15.3 (POCH2CH3);31P NMR:
δ ) 29.5 (s).
Hybrid Monomer MAA-PA-APTES (3b) (Scheme 11).
The appropriate amine PA-APTES (8.924 g, 0.023 mol),
triethylamine (2.577 g, 0.025 mol) and DMAP (0.212 g, 0.002
mol) were dissolved under Ar in 60 mL of dry dichlormethane.
Under cooling (0-5 °C), methacryloyl chloride (1.582 g, 0.015
mol) dissolved in 20 mL of dichlormethane was added during
1 h. After the mixture was stirred overnight, the precipitate
was filtered off. Dichlormethane was evaporated and column

Macromolecules, Vol. 38, No. 23, 2005
Phosphonate-Functional Compounds 9555
4 mm), then slightly overfilling them and gently compressing
them between two glass plates. The specimens were polym-
erized with a curing device (Spektrum 800, wavelength (λmax
) 465 nm, light intensity 800 mW/cm2) for 40 s on both ends
of the specimens. Rod like test specimens (height and width 2
mm, length 2.5 mm) were prepared in the same manner except
for the polymerization procedure. Photochemical polymeriza-
tion was carried out in a Triad photochemical curing unit (λmax
) 470 nm, Dentsply De Trey, Konstanz, Germany) within 3
min on both ends of the specimens. All test specimens were
gently removed from the molds and stored in deionized water
at 37 °C for 24 h before testing.
Transmission Electron Microscopy (TEM). The samples
were prepared by dropping solutions of nanoparticles on carbon
grids. After drying in a vacuum homogeneous films were
obtained. The TEM measurements were carried out with a
LEO CEM 912 transmission electron microscope applying an
acceleration voltage of 120 kV.26,27 The particle size was
determined by the analysis of numerous TEM images using
the iTEM-software of SIS.
Environmental Scanning Electron Microscope (ESEM).
The ESEM measurements of fractured surfaces of the com-
posites were carried out with a ESEM 2020 environmental
scanning electron microscope applying a LaB6-cathode and an
acceleration voltage of 23 kV. The images were obtained by
gaseous secondary electron detector at pressures of 666-1067
Pa.28
Methods. NMR. 1H, 13C and 31P NMR spectra were
recorded in CDCl3 at concentrations of 250 g/L on a Bruker
ARX 300 spectrometer, operating at 300, 75.4, and 59,6 MHz,
respectively.
The solid state 29Si CP MAS NMR spectra was run on a
Bruker Avance 500 spectrometer at 99.3 MHz with cross-
polarization on samples spun at 10 kHz.
Viscosities. Rheological properties were determined using
a Bohlin CS50 rheometer with water-bath temperature control.
Cone-and-plate geometry was used with 1.5 cm3 being trans-
ferred to the plate at room temperature. Measurements
viscosity were made with the instrument in continuous-shear
mode, with at least 10 min allowed at room temperature for
equilibration.
FAB-MS. Fast atom bombardment mass spectra were
obtained with a double focusing Finnigan MAT 312/AMD 5000
mass spectrometer equipped with a Cs ion source.
GC-MS. Measurements were carried out with a Thermo
Quest Trace 2000 Series GC connected with Voyager GC/MS
of Thermo Quest Finnigan. Spectra were recorded in MeOH
at concentrations of 5 wt %.
References and Notes
(1) Cook, W. D.; Tyas, M. J. Biomaterials 1985, 6, 362.
(2) Bowen, R. L.; Marjenhoff, W. A. Adv. Dent. Res. 1992, 6, 44.
(3) Bowen, R. L.; Marjenhoff, W. A. US Patent 3,066,112.
(4) Nunes, T. G.; Pires, R.; Perdigao, J.; Amorim, A.; Polido, M.
Polymer 2001, 42, 8051.
(5) Schmidt, H. CHIUZ 2001, 35, 176.
(6) Paul, P. P. US Patent 6,005,028.
(7) Mu¨h, E.; Frey, H.; Klee, J. E.; Mu¨lhaupt, R. Adv. Funct.
Mater. 2001, 11, 425.
(8) Mu¨h, E.; Marquardt, J.; Klee, J. E.; Frey, H.; Mu¨lhaupt, R.
Macromolecules 2001, 34, 5778.
(9) Mu¨h, E.; Weickmann, H.; Klee, J. E.; Frey, H.; Mu¨lhaupt, R.
Macromol. Chem. Phys. 2001, 202, 3484.
(10) Mu¨h, E.; Stieger, M.; Klee, J. E.; Frey, H.; Mu¨lhaupt, R. J.
Polym. Sci.: Part A: Polym. Chem. 2001, 39, 4274.
(11) Mou, L.; Singh, G. J.; Nicholson, W. Chem. Commun. 2000,
345.
MALDI-TOF. (matrix assisted laser desorption ionization-
time of light) spectra were obtained with a REFLEX II mass
spectrometer (Bruker-Franzen). Appropriate amounts of ma-
trix (cyanohydroxy cinnamic acid) and polymer was dissolved
in CHCl3. The metal ion Li+ often required for enhanced
cationization was added as their inorganic salt (LiCl), and 1
µL of the whole solution was then applied to a sample holder
and allowed to dry. The resulting homogeneous solid mixture
was then introduced into the ion source of the mass spectrom-
eter and irradiated by a pulsed UV laser (accelerating voltage
20 kV).
Mechanical Data. The compressive strengths and yield
stresses were tested using the method “compression test with
yielding point” according to the ISO 9917 and determined with
a Zwick testing machine Z010. The specimens were placed with
their flat ends between the plates of the testing machine, so
that compressive load was applied along the long axis of the
specimens. The force-displacement curve was analyzed with
testXpert (version 10.11) software to obtain the yield stress.
The compressive strength was calculated from the maximum
applied load. The flexural test was performed according to ISO
4049 using a Zwick instrument Z010. The flexural strengths
was calculated from the maximum load. Analyzing the force-
displacement curve with testXpert software resulted in Young’s
modulus.
(12) Zeuner, F.; Moszner, N.; Vo¨lkel, T.; Vogel, K.; Rheinberger,
V. Phosphorus, Sulfur Silicon 1999, 144-146, 133.
(13) Moszner, N.; Zeuner, F.; Rheinberger, V. Macromol. Symp.
2001, 175, 133.
(14) Moszner, N.; Zeuner, F.; Fischer, U.; Rheinberger, V. Mac-
romol. Chem. Phys. 1999, 200, 1062.
(15) Moszner, N.; Zeuner, F.; Pfeiffer, S.; Schurte, I.; Rheinberger,
V.; Drache, M. Macromol. Mater. Eng. 2001, 286, 225.
(16) Moszner et al., N. Macromol. Chem. Phys. 1996, 197, 81.
(17) Rodriguez et al., S. Tetrahedron 2002, 58 (6), 1185.
(18) Moszner, N.; Vo¨lkel, T.; Cramer von Clausbruch, S.; Geiter,
E.; Batliner, N.; Rheinberger, V. Macromol. Mater. Eng. 2002,
287, 339.
(19) Nakabayashi, N.; Kanda, K. J. Dent. Mat. 1987, 6, 396.
(20) Nikaido, T.; Nakabayashi, N. J. Dent. Mat. 1987, 6, 690.
(21) Fusayama et al., T. J. Dent. Res. 1979, 58, 1364.
(22) Dekkers, M. E.; Heikens, D. J. Mater. Sci. 1984, 19, 3271.
(23) Kawaguchi, T.; Raymond, R. A. Polymer 2003, 44, 4229.
(24) Pukanszky, B.; Tu¨do¨s, F. Macromol. Chem., Macromol. Symp.
1989, 28, 16.
(25) Pekete, E.; Pukanszky, B.; Toth, A. J. Colloid Interface Sci.
1990, 135, 200.
(26) Sawyer, L.; Grubb, D. Polymer Microscopy, Chapman and
Hal: new York, 1987.
(27) Gruehn, R.; Ross, R. CHIUZ 1987, 18, 813.
(28) Cameron, R. TRIP 1994, 2, 116.
MA047526E