Synthesis of methacrylate-functionalized phosphonates and phosphates with long alkyl-chain spacers and their self-aggregation in aqueous solutions

Article abstract of DOI:10.1007/s00706-008-0045-y

Polymerizable amphiphilic organophosphorous compounds were synthesized and their self-aggregation behavior was investigated. The studied molecules contain a hydrophilic phosphorus end group, an alkyl chain spacer with a variable length from 3 to 11 CH₂ groups and a polymerizable methacrylic group at the other chain end. Thus, the molecules represent a class of polymerizable surfactants. Two different reaction methods were used; either unsaturated alcohols or bromine-containing alcohols were applied as starting compounds for the preparation of the organophosphorous surfactants. The self-aggregation and micelle formation of the prepared compounds were investigated in aqueous solution by dynamic light scattering measurements. The critical micelle concentration of the P-containing amphiphiles was in all cases smaller than 0.040 mol/l and strongly dependent on the polarity of the phorphorous head group and the chain length of the spacer. Graphical abstract: [Figure not available: see fulltext.] The synthesis of organophosphorous amphiphiles as surface active monomers for the modification of metal oxide surfaces is presented. The spacer between the phosphorous head group and the methacrylate group was varied with regard to their length and composition. The self-aggregation behavior of these methacrylate-functionalized phosphates and phosphonates surfactants was investigated.

Full text of DOI:10.1007/s00706-008-0045-y

Monatsh Chem (2009) 140:413–422
DOI 10.1007/s00706-008-0045-y
ORIGINAL PAPER
Synthesis of methacrylate-functionalized phosphonates
and phosphates with long alkyl-chain spacers and their
self-aggregation in aqueous solutions
´
Denisa Francova Æ Guido Kickelbick
Received: 18 July 2008 / Accepted: 22 July 2008 / Published online: 20 September 2008
Ó Springer-Verlag 2008
Abstract Polymerizable amphiphilic organophosphorous
compounds were synthesized and their self-aggregation
behavior was investigated. The studied molecules contain a
hydrophilic phosphorus end group, an alkyl chain spacer
with a variable length from 3 to 11 CH2 groups and a
polymerizable methacrylic group at the other chain end.
Thus, the molecules represent a class of polymerizable
surfactants. Two different reaction methods were used;
either unsaturated alcohols or bromine-containing alcohols
were applied as starting compounds for the preparation of
the organophosphorous surfactants. The self-aggregation
and micelle formation of the prepared compounds were
investigated in aqueous solution by dynamic light scatter-
ing measurements. The critical micelle concentration of
the P-containing amphiphiles was in all cases smaller
than 0.040 mol/l and strongly dependent on the polarity of
the phorphorous head group and the chain length of the
spacer.
Organophosphonates and -phosphates have generally a
large variety of technological applications, i.e., flame re-
tardancy [1, 2], organic synthesis [3], dental materials [4],
and adhesion promotors for paints, lacquers and adhesives
[5, 6]. They are used also in the composition of glasses,
fibers and films with high mechanical resistance [5], syn-
thetic ion-exchangers [7, 8], etc. Furthemore, these systems
play a major role in the attachment of biological molecules
[9, 10] to surfaces, or the connection of organic materials to
biological interfaces, which is technologically used, for
example, in dental materials [11].
For many scientific and technological applications, it is
necessary that the alkyl chain of the organophosphorous
derivatives contains an additional organic functional group
that allows further chemical transformations. Particularly
polymerizable groups are interesting for nanocomposite or
hybrid material applications. Most of organophosphonates
and -phosphates containing polymerizable groups known in
the literature, such as acrylate-based systems, consist of a
short alkyl spacer between the phosphate or phosphonate
and the polymerizable group, e.g., diethyl(acryloy-
loxyethyl)phosphate (DEAEP), diethyl(acryloyloxymethyl)
phosphonate (DEAMP), diethyl-2-(methacryloyloxyethyl)
phosphate (DEMEP), and dimethyl(acryloyloxymethyl)
phosphonate (DMAMP) [12, 13], etc. However, some of
the above-mentioned aplications require long alkyl chains
that improve, for example, the hydrophobicity of the
compounds [4]. Long alkyl groups connected to the quite
polar phosphorous-containing end groups can also promote
the self-association of such molecules and the formation of
micelles, which make them useful compounds as emulsi-
fiers and in detergent formulations [14, 15].
Keywords Functional monomers ꢀ Amphiphiles ꢀ
Self-aggregation ꢀ Organophosphorous compounds
Introduction
For the past years, organophosphorous monomers and
polymers have been the subject of intensive research,
with massive number of papers published annually.
´
D. Francova ꢀ G. Kickelbick (&)
Institute of Materials Chemistry,
In the literature only a few descriptions of synthetic
procedures for the formation of methacrylated phosphonic
acids and esters with long alkyl chains can be found.
Vienna University of Technology,
Getreidemarkt 9-165, 1060 Vienna, Austria
e-mail: guido.kickelbick@tuwien.ac.at
123

´
D. Francova, G. Kickelbick
414
Synthesis of 2-methyl-acrylic acid (diethoxy-
phosphoryl)-alkyl ester
Boutevin et al. [16] investigated the synthesis of various
phosphonic acids and esters containing acrylic and meth-
acrylic groups with a different spacers between the
phosphorous and polymerizable group, e.g., phosphonated
methacrylates containing urethane group [17] synthesized
by reacting the isocyanatoethyl methacrylate and a phos-
phonate alcohol, or thia-alkyl group [18] synthesized
by monoaddition of thioglycol acid onto dimethylvinyl
phosphonate followed by the reaction with glycidyl me-
thycrylate. This group [19] also performed the synthesis
of methacrylated phosphonates by the telomerization of
unsaturated alcohol with dialkylhydrogenphosphonate or
radical addition of dialkylhydrogenphosphonate on the
alkenyl acetate, by using di-tert-butyl peroxide as initiator.
Several patents, particularly in the field of dental materials,
also describe the synthesis of methacrylated phosphoric
acids.
The synthesis of 2-methyl-acrylic acid (diethoxy-phos-
phoryl)-alkyl esters with a different length of the alkyl
chain was carried out according to a procedure published
by Boutevin et al. [19]. Here we give a typical reaction for
the synthesis of 2-methyl-acrylic acid 3-(diethoxy-phos-
phoryl)-propyl ester:
Acetylation of alkenol
In a 250-ml three-necked round-bottom flask supplied with a
condenser and a pressure-equalizing dropping funnel, 5.8 g
(0.10 mol) allyl alcohol and 13.2 g (0.13 mol) triethylamine
solubilized in 52.7 g (0.62 mol) dichloromethane was
mixed under an argon atmosphere. The reaction mixture was
cooled at 0 °C in an ice bath, and 10.2 g (0.13 mol) acetyl
chloride dissolved in 26.3 g (0.31 mol) dichloromethane
was added dropwise. Afterwards, the reaction mixture was
stirred for 12 h at 40 °C. The formed white precipitate was
filtered and washed with dichloromethane. The organic
phase was washed with 5 wt% solution of NaHCO3 and with
water to gain neutral pH. After evaporation of the solvent,
traces of solvent were eliminated under vacuum; 9.3 g (93%
yield) of a colorless liquid were obtained.
In this paper, we investigated some novel synthetic
routes to such materials with a specific focus on highly
effective methods for the synthesis of organophosphonates
and -phosphates that contain polymerizable groups. The
alkyl spacer between the phosphorous and the methacrylate
group was varied with regard to its length and composition.
Self-assembly processes of these surfactant monomers into
micelles were also investigated.
Vinyl acetate
1H NMR (CDCl3): d = 2.0 (s, H3), 4.5 (d, H2, J = 5.5 Hz),
5.2 (dd, H2), 5.9 (m, H1).
Experimental
The reagents were supplied by Aldrich and used without
further purification. The 1H, 31P and 13C spectra were
recorded at room temperature using a Bruker Avance 300
instrument (1H at 300.13 MHz, 13C at 75.47 MHz)
equipped with a 5-mm, inverse-broadband probe head with
a z-gradient unit in CDCl3 as solvent. The chemical shifts
are given in ppm. FT-IR spectra were recorded on a Bruker
Tensor 27 instrument working in ATR MicroFocusing
MVP-QL with a ZnSe crystal. The software used for
analysis was OPUSTM version 4.0. Dynamic light scat-
tering (DLS) was used to analyze the average particle size
of the micelles formed in aqueous solution. DLS mea-
surements were performed with an ALV/CGS-3 compact
goniometer system with an ALV/LSE-5003 light scatter-
ing electronics and multiple s digital correlator at 25 °C.
The light source was a Uniphase cylindrical 22-mW
HeNe-laser operating at a wavelength of 632.8 nm
with vertically polarized light. The scattering angle was
fixed at 90°. Gas chromatography was performed with a
Finnigan Voyager instrument, equipped with a flame-
ionizing detector using an achiral column BGB5
(30 m 9 0.25 mm 9 0.25 lm). Elemental analysis was
carried out at the Microanalytical Laboratory at the
University of Vienna.
Undec-8-enyl acetate
1H NMR (CDCl3): d = 1.3 (m, H12), 1.6 (m, H2), 2.0 (s,
H5), 4.0 (t, H2, J = 6.7 Hz), 5.0 (dd, H2), 5.8 (m, H1).
Synthesis of acetic acid (diethoxy-phosphoryl)-alkyl
ester
In a 100-ml three-necked round-bottom flask fitted with a
condenser, a system of argon bubbling and a pressure-
equalizing dropping funnel, 47.4 g (0.343 mol) diethyl
phosphite was introduced. The bubbling argon through the
reaction mixture using a capillary and the temperature of
120 °C were maintained during the whole reaction. The
mixture of 9.3 g (0.093 mol) vinyl acetate, 0.8 g
(4.9 mmol) AIBN and 13.4 g (0.097 mol) diethyl phos-
phite was introduced dropwise. The reaction mixture was
kept under stirring at 120 °C for 2 h. The obtained reaction
product was distilled under vacuum to eliminate the excess
of diethyl phosphite and other potential side products;
21.9 g (99% yield) of a colorless liquid were obtained.
Arbuzov reaction: In a 100-ml flask fitted with a con-
denser, 40.4 g (0.243 mol) triethyl phosphite and 12.5 g
(0.06 mol) 5-bromopentyl acetate were mixed and heated
123

Synthesis of methacrylate-functionalized phosphonates and phosphates
415
to reflux for 16 h. Afterwards, the mixture was distilled
under vacuum to eliminate the excess of triethyl phosphite
and other side products; 13.4 g (76% yield) of a colorless
liquid were obtained.
(0.11 mol) methacryloyl chloride dissolved in 37.4 g
(0.44 mol) dichloromethane was added dropwise to the
mixture. At the end of the addition, the reaction mixture
was kept under stirring for 2 days at room temperature.
After 2 days, a white precipitate was filtered. The solvent
was evaporated, and the crude reaction mixture was poured
into ether. The organic phase was washed three times with
water saturated with sodium chloride. After evaporation
under vacuum, 22.8 g (94% yield) of pale yellow liquid
2-methyl-acrylic acid 3-(diethoxy-phosphoryl)-propyl ester
were isolated.
Acetic acid 3-(diethoxy-phosphoryl)-propyl ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 7.0 Hz), 1.8 (m,
H4), 2.0 (s, H3), 4.1 (m, H6); 31P NMR (CDCl3): d = 31.22
[R-P(O)(OEt)2].
Acetic acid 5-(diethoxy-phosphoryl)-pentyl ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 7.0 Hz), 1.4 (m,
H2), 1.7 (m, H6), 2.0 (s, H3), 4.1 (m, H6); 31P NMR
(CDCl3): d = 32.06 [R-P(O)(OEt)2].
2-Methyl-acrylic acid 3-(diethoxy-phosphoryl)-propyl
ester
Acetic acid 11-(diethoxy-phosphoryl)-undecyl ester
1H NMR (CDCl3): d = 1.3 (m, H20), 1.6 (m, H6), 2.0 (s,
H3), 4.1 (m, H6); 31P NMR (CDCl3): d = 32.43 [R-P(O)
(OEt)2].
1H NMR (CDCl3): d = 1.3 (t, H6, J = 8.9 Hz), 1.8 (m,
H4), 1.9 (s, H3), 4.1 (m, H6), 5.5 (s, H1), 6.0 (s, H1); 31P
NMR (CDCl3): d = 31.40 [R-P(O)(OEt)2]. 13C NMR
(CDCl3): d = 167.22, 136.15, 125.62, 64.13, 64.03
(J = 7.3 Hz), 61.84, 61.74 (J = 7.7 Hz), 23.11, 21.21
(J = 143 Hz), 22.09, 22.01 (J = 6 Hz), 18.27, 16.45,
16.35 (J = 7.1 Hz). IR m (cm-1): 2,984, 1,717 (C=O),
1,636 (C=C), 1,454, 1,319, 1,296, 1,240 (P=O), 1,160,
1,022 (P–O), 957, 814, 786.
Synthesis of (hydroxy-alkyl)-phosphonic acid diethyl
ester
In a 250-ml three-necked round-bottom flask equipped
with a reverse condenser, 21.9 g (0.092 mol) acetic acid 3-
(diethoxy-phosphoryl)-propyl ester and 1 g (0.018 mol)
potassium hydroxide in 98.4 g (3.07 mol) methanol were
mixed under an argon atmosphere. The mixture was stirred
under reflux for 3 days; 18.0 g (99% yield) of a colorless
liquid were obtained.
Elemental analysis: C11H21O5P: calculated: C 50.00, H
8.01; found: C 49.66, H 7.89.
2-Methyl-acrylic acid 5-(diethoxy-phosphoryl)-pentyl
ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 7.0 Hz), 1.4 (m,
H2), 1.7 (m, H6), 1.9 (s, H3), 4.1 (m, H6), 5.5 (s, H1), 6.0 (s,
H1); 31P NMR (CDCl3): d = 32.49 [R-P(O)(OEt)2]. 13C
NMR (CDCl3): d = 167.46, 136.37, 125.33, 64.18, 61.68,
61.58 (J = 7.5 Hz), 28.16, 27.15, 26.88, 26.63, 24.69
(J = 145 Hz), 22.17, 22.09 (J = 6 Hz), 18.31, 16.47,
16.38 (J = 7.2 Hz). IR m (cm-1): 2,982, 2,954, 1,716
(C=O), 1,636 (C=C), 1,455, 1,320, 1,296, 1,229 (P=O),
1,162, 1,024 (P–O), 957, 814, 787.
(3-Hydroxy-propyl)-phosphonic acid diethyl ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 8.9 Hz), 1.8 (m,
H4), 3.6 (t, H2, J = 7.0 Hz), 4.1 (m, H4); 31P NMR
(CDCl3): d = 31.35 [R-P(O)(OEt)2].
(5-Hydroxy-pentyl)-phosphonic acid diethyl ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 7 Hz), 1.4 (m, H2),
1.7 (m, H6), 3.6 (t, H2, J = 6.2 Hz), 4.1 (m, H4); 31P NMR
(CDCl3): d = 32.47 [R-P(O)(OEt)2].
Elemental analysis: C13H25O5P: calculated: C 53.42, H
8.62; found: C 53.50, H 8.11.
(11-Hydroxy-undecyl)-phosphonic acid diethyl ester
1H NMR (CDCl3): d = 1.3 (m, H20), 1.6 (m, H6), 3.6 (t,
H2, J = 6.5 Hz), 4.1 (m, H4); 31P NMR (CDCl3):
d = 32.81 [R-P(O)(OEt)2].
2-Methyl-acrylic acid 11-(diethoxy-phosphoryl)-undecyl
ester
1H NMR (CDCl3): d = 1.3 (m, H20), 1.6 (m, H6), 1.9 (s, H3),
4.1 (m, H6), 5.5 (s, H1), 6.0 (s, H1); 31P NMR (CDCl3):
d = 32.76 [R-P(O)(OEt)2]. 13C NMR (CDCl3): d = 167.66,
136.51, 125.16, 64.82, 61.59, 61.49 (J = 7.5 Hz), 29.45,
29.21, 28.57, 26.39, 24.46 (J = 145 Hz), 25.95, 22.36, 22.28
(J = 6.2 Hz), 18.34, 16.50, 16.40 (J = 7.2 Hz). IR m
(cm-1): 2,928, 2,855, 1,717 (C=O), 1,636 (C=C), 1,455,
1,320, 1,296, 1,243 (P=O), 1,162, 1,055, 1,025 (P–O), 957,
814, 786.
Synthesis of 2-methyl-acrylic acid (diethoxy-
phosphoryl)-alkyl ester
In a 500-ml three-necked round-bottom flask fitted with a
condenser, a system of argon bubbling and a pressure-
equalizing dropping funnel, 18 g (0.092 mol) (3-hydroxy-
propyl)-phosphonic acid diethyl ester, 11.1 g (0.11 mol)
triethylamine and 262.4 g (3.09 mol) dichloromethane
were introduced. The reaction mixture was purged by
argon and cooled to 0 °C in an ice bath. Then 11.5 g
Elemental analysis: C19H37O5P: calculated: C 60.62, H
9.91; found: C 60.24, H 10.00.
123

´
D. Francova, G. Kickelbick
416
Synthesis of 2-methyl-acrylic acid (diethoxy-
phosphoryloxy)-alkyl ester
2-Methyl-acrylic acid 3-(diethoxy-phosphoryloxy)-propyl
ester
1H NMR (CDCl3): d = 1.3 (t, H6, J = 7.0 Hz), 1.9 (s, H3),
2.0 (t, H2, J = 6.2 Hz), 4.1 (m, H6), 4.2 (t, H2, J = 6.2 Hz),
5.5 (s, H1), 6.0 (s, H1); 31P NMR (CDCl3): d = -0.94
[R(O)-P(O)(OEt)2]. 13C NMR (CDCl3): d = 167.23,
136.15, 125.54, 64.08, 63.99 (J = 6.8 Hz), 63.88, 63.78
(J = 6.9 Hz), 60.67, 29.58, 29.47 (J = 8.4 Hz), 18.26,
16.15, 16.05 (J = 8 Hz). IR m (cm-1): 2,983, 2,932, 1,718
(C=O), 1,637 (C=C), 1,454, 1,319, 1,296, 1,263 (P=O),
1,164, 1,023 (P–O), 975, 815.
Synthesis of 2-methyl-acrylic acid hydroxy-alkyl ester
In the first step, 7.5 g (0.069 mol) sodium methacrylate
and 4.7 g (0.050 mol) 3-chloro-1-propanol in 117.8 g
(2.87 mol) acetonitrile were introduced in a 250-ml round-
bottom flask supplied with a condenser. The methacrylate
was stabilized with hydroquinone monomethylether 14 mg
(0.11 mmol). As a catalyst, tricaprylylmethylammonium
chloride (AliquatÒ 336) was used (5% by weight). The
mixture was refluxed for 24 h. After cooling, the mixture
was filtered and extracted with CH2Cl2. The organic phase
was washed with water, dried with MgSO4 and concen-
trated. The residue was purified by distilation under reduced
pressure and by column chromatography with the system of
solvents dichlormethane:methanol (100:1); 4.3 g (60%
yield) of a colorless liquid were obtained.
Elemental analysis: C11H21O6P: calculated C 47.14, H
7.55; found: C 47.25, H 7.32.
2-Methyl-acrylic acid 6-(diethoxy-phosphoryloxy)-hexyl
ester
1H NMR (CDCl3): d = 1.3 (m, H10), 1.7 (m, H4), 1.9 (s,
H3), 4.15 (m, H8), 5.5 (s, H1), 6.0 (s, H1); 31P NMR
(CDCl3): d = -0.92 [R(O)-P(O)(OEt)2]. 13C NMR
(CDCl3): d = 167.50, 136.44, 125.24, 67.47, 67.38
(J = 7.2 Hz), 64.54, 63.71, 63.62 (J = 7.0 Hz), 30.20,
30.09, 25.57, 25.13, 18.30, 16.18, 16.07 (J = 8 Hz). IR m
(cm-1): 2,983, 2,934, 1,717 (C=O), 1,636 (C=C), 1,455,
1,320, 1,295, 1,273 (P=O), 1,164, 1,025 (P–O), 973, 816.
2-Methyl-acrylic acid 3-hydroxy-propyl ester
1H NMR (CDCl3): d = 1.8 (m, H2), 1.9 (s, H3), 3.7 (t, H2,
J = 6 Hz), 4.3 (t, H2, J = 6.0 Hz), 5.5 (s, H1), 6.1 (s, H1).
2-Methyl-acrylic acid 6-hydroxy-hexyl ester
1H NMR (CDCl3): d = 1.3 (m, H4), 1.6 (m, H4), 1.9
(s, H3), 3.7 (t, H2, J = 6.5 Hz), 4.3 (t, H2, J = 6.5 Hz), 5.5
(s, H1), 6.1 (s, H1).
Elemental analysis: C14H27O6P: calculated: C 52.17, H
8.44; found: C 52.02, 8.52 H.
2-Methyl-acrylic acid 8-hydroxy-octyl ester
1H NMR (CDCl3): d = 1.45 (m, H12), 1.9 (s, H3), 3.7
(t, H2, J = 6.5 Hz), 4.3 (t, H2, J = 6.7 Hz), 5.5 (s, H1), 6.1
(s, H1).
2-Methyl-acrylic acid 8-(diethoxy-phosphoryloxy)-octyl
ester
1H NMR (CDCl3): d = 1.3 (m, H20), 1.7 (m, H6), 1.9 (s,
H3), 4.2 (m, H8), 5.5 (s, H1), 6.0 (s, H1); 31P NMR (CDCl3):
d = -0.71 [R(O)-P(O)(OEt)2]. 13C NMR (CDCl3):
d = 167.54, 136.50, 125.17, 67.54, 67.64 (J = 7.3 Hz),
64.72, 63.68, 63.59 (J = 6.9 Hz), 30.27, 30.16, 29.09,
28.54, 25.87, 25.34, 18.31, 16.18, 16.07 (J = 8 Hz). IR m
(cm-1): 2,931, 2,857, 1,717 (C=O), 1,637 (C=C), 1,455,
1,321, 1,296, 1,261 (P=O), 1,163, 1,026 (P–O), 975, 814.
Synthesis of 2-methyl-acrylic acid (diethoxy-
phosphoryloxy)-alkyl ester
In a 100-ml three-necked round-bottom flask supplied
with a condenser and a pressure-equalizing dropping
funnel, 4.3 g (0.03 mol) 2-methyl-acrylic acid 3-hydroxy-
propyl ester and 2.1 g (0.021 mol) triethylamine solubi-
lized in 51.0 g (0.6 mol) dichloromethane were mixed
under an argon atmosphere. The reaction mixture was
cooled at 0 °C in an ice bath. Then 3.8 g (0.022 mol)
diethyl chlorophosphate dissolved in 7.3 g (0.086 mol)
CH2Cl2 was added dropwise. Then 0.95 g (0.012 mol) of
pyridine was added to the reaction mixture. Afterwards
the solution was stirred for 3 days at room temperature.
The formed white precipitate was filtered, and the solvent
was evaporated. The crude reaction mixture was poured
into ether. The organic phase was washed three times with
water saturated with sodium chloride. After distillation
under vacuum, 5.8 g (71% yield) of pale yellow liquid
2-methyl-acrylic acid 3-(diethoxy-phosphoryloxy)-propyl
ester were obtained.
Elemental analysis: C16H31O6P: calculated: C 54.85, H
8.92; found: C 55.03, H 8.87.
Cleavage of phosphonic and phosphoric esters
The cleavage of esters was carried out following a proce-
dure published by Gutierrez et al. [20].
In the first step, 2.5 g (6.6 mmol) 2-methyl-acrylic acid
11-(diethoxy-phosphoryl)-undecyl ester or 2.3 g 2-methyl-
acrylic acid 8-(diethoxy-phosphoryloxy)-octyl ester and
53 mg (0.6 mmol) ethylacetate in 5.3 g (0.062 mol)
dichloromethane were stirred at 25 °C in a 10-ml round-
bottom flask supplied with a precision seal septum. About
2.1 g (0.014 mol) trimethylbromosilane was slowly added
by a syringe through the septum into solution. At the end of
123

Synthesis of methacrylate-functionalized phosphonates and phosphates
417
addition, the reaction mixture was stirred for 1 h at room
temperature. The second step was carried out in the same
round-bottom flask after evaporation of the solvent.
About 4.2 g (9.1 mmol) bis-trimethylsilyl(methacryloylox-
yalkyl)phosphonate or 4.0 g bis-trimethylsilyl(methacry-
loyloxyalkyl)phosphate were dissolved in 2.1 g (0.064 mol)
methanol, and the reaction mixture was kept under stirring
at room temperature for 1 h. About 2.0 g and 1.85 g
(95% yield) of viscous yellow liquid 2-methyl-acrylic acid
11-phosphono-undecyl ester and 2-methyl-acrylic acid
8-phosphonooxy-octyl ester was obtained, respectively.
(around 5 min) in an ultrasound bath. The measurements
have been carried out at room temperature after 20 min
of cellaring to give the systems to equilibrate after
sonication.
Results and discussion
Methacrylated phosphonates
The critical step in the synthesis of organophosphonates is
the formation of the C–P bond. Two different methods
have proven appropriate for this synthetic step: the Arbu-
zov reaction between an alkyl bromide and triethyl
phosphate, or a radical addition of a diethyl phosphate to an
unsaturated bond. Quite high temperatures have to be used
for the Arbuzov reaction, therefore it is limited to tem-
perature-stable functional groups and often cannot be used
in the presence of polymerizable bonds that can undergo
thermal polymerization. The radical addition requires the
presence of alkenyl bonds in the precursor. The synthetic
procedure, Arbuzov reaction or radical addition, was cho-
sen depending on the commercial availability of the alkyl
chain precursors, which are a-x-bromo alcohols for the
Arbuzov reaction and a-x-alkenols for the radical addition.
Spacer length of 3 and 11 CH2 groups was prepared using
the radical addition method, and for the spacer with 5 CH2
groups the Arbuzov reaction was used.
2-Methyl-acrylic acid 8-phosphonooxy-octyl ester
1H NMR (CDCl3): d = 1.3 (m, H8), 1.7 (m, H4), 1.9 (s,
H3), 3.6 (t, H2, J = 6.7 Hz), 4.1 (t, H2, J = 6.5 Hz), 5.5 (s,
H1), 6.0 (s, H1); 31P NMR (CDCl3): d = -51.13 [R(O)-
P(O)(OH)2]. 13C NMR (CDCl3): d = 167.57, 136.49,
125.27, 64.74, 63.42, 63.31 (J = 8.0 Hz), 32.73, 29.03,
28.62, 28.54, 28.047, 25.84, 18.34. IR m (cm-1): 2,932,
2,857, 1,717 (C=O), 1,636 (C=C), 1,454, 1,320, 1,296
(P=O), 1,163, 1,010 (P–O), 957, 849, 814.
Elemental analysis: C12H23O6P: calculated C 48.98, H
7.88; found: C 48.98, H 8.04.
2-Methyl-acrylic acid 11-phosphono-undecyl ester
1H NMR (CDCl3): d = 1.3 (m, H18), 1.6 (m, H2), 1.9 (s, H3),
4.1 (t, H2, J = 6.5 Hz), 5.5 (s, H1), 6.0 (s, H1); 31P NMR
(CDCl3): d = 37.35 [R-P(O)(OH)2]. 13C NMR (CDCl3):
d = 167.62, 136.50, 125.20, 64.84, 29.69, 29.43, 29.29,
29.20, 28.57, 25.94, 22.35, 22.24 (J = 6.2 Hz), 18.32. IR m
(cm-1): 2,922, 2,953, 1,718 (C=O), 1,636 (C=C), 1,458,
1,303 (P=O), 1,149, 1,063 (P–O), 990, 935, 716.
Methacrylated organophosphonates with various alkyl
chain lengths by radical addition method were synthesized
applying a four-step procedure (Scheme 1). Starting point
of the synthesis was a previously published procedure [19]
that we optimized and extended.
Elemental analysis: C15H29O5P: calculated: C 56.24, H
9.12; found: C 56.51, H 9.22.
The first step is the protection of the alcohol function of
the unsaturated alcohol, which could lead to an undesired
side reaction during the following addition of dialkyl
phosphite to the double bond. Acylation with acetyl chlo-
ride was used for the protection of the hydroxyl group
under Schotten–Baumann conditions, which was carried
out at low temperature with high yields.
Critical micelle concentration measurement
The critical micelle concentration (CMC) was measured in
distilled water by DLS. Several solutions have been
prepared at different concentrations in the range of 0.1–
0.1 9 10-5 mol/L by addition of the appropriate amount of
acid to an aqueous solution followed by a brief sonication
The second step in the synthesis is the addition of the
phosphite to the alkenyl acetate. Some methods describing
Scheme 1
O
Cl
O
HP(O)(OEt)2
AIBN
NEt3/CH2Cl2
O
O
P
m
HO
+
m
n
O
O
O
O
KOH/CH3OH
Cl
O
O
O
n = 3, 11
m = n-2
O
O
O
HO
n
P
P
O
O
NEt3/CH2Cl2
n
O
123

´
D. Francova, G. Kickelbick
418
direct addition of dialkyl phosphite [21, 22], respectively
tetraalkyl [23] pyrophosphite to the unsaturated compounds
can be found in the literature. These reactions are referred
to as telomerization reactions, which start from the creation
of radicals generated mostly by photolysis [21, 22] or
hydrogen absorption to the dialkyl phosphite [23]. How-
ever, this method creates also non-phosphonated radicals
and leads to undesirable by-products. Radical addition of
diethyl phosphite to the alkenyl acetate seems to be the
method of choice for the desired molecules due to its high
selectivity and yields. Boutevin et al. [19] described pre-
viously a similar reaction between 10-undecenol and
diethyl phosphite, respectively, 10-undecenoic acid and
diethyl phosphite. They based their procedure on the work
of Pelaprat et al. [24], who have realized the addition by
using di-tert-butyl peroxide at 140 °C. The authors have
noticed the presence of secondary phosphonated products.
Boutevin et al. [19] in their work studied both possibilities,
the direct telomerization of unsaturated compounds
with dialkylhydrogenphosphonate and radical addition
of dialkylhydrogenphosphonate on the undec-10-enyl ace-
tate, by using di-tert-butyl peroxide at 135 °C for 10 h.
They observed in both cases secondary products, which
were probably formed by the autocondensation of initial
unsaturated products. For this addition, we used azobisi-
sobutyronitrile (AIBN), which is very selective. After 2 h
under reflux, the targeted acetic acid (diethoxy-phos-
phoryl)-alkyl ester was obtained in 99% yield without
formation of secondary products.
after 3.5 days the total disappearance was detected with a
product yield of 99%.
The last step was the methacrylation of (hydroxy-alkyl)-
phosphonic acid diethyl ester. The methacrylation was
often carried out with an excess of methacrylic anhydride
[25, 26]. This esterification was performed under mild
conditions. However, the kinetic was very slow, and only
low conversion was achieved. Moreover, methacrylic
anhydride can hydrolyze, yielding methacrylic acid. The
esterification was also previously performed with methac-
ryloyl chloride in p-dioxane with pyridine [27] or in
dichloromethane [19] with triethylamine. In this work, the
reaction was carried out under previously [19] reported
1
conditions. Methacrylation was confirmed by IR and H
NMR. IR of the methacrylated phosphonate showed ester
carbonyl absorption at 1,719 cm-1. 1H NMR exhibited two
doublets at 5.5 and 6.0 ppm characteristic for methacrylic
protons and the singlet at 1.9 ppm characteristic for CH3
protons of the methacrylate group. Also, the disappearance
of the triplet at 3.6 ppm of the CH2 protons in a-position of
the hydroxyl group was observed. The advantage of this
procedure is a good reproducibility with a high overall
yield, which is 88%.
In case of the availability of bromo alcohol or bro-
moalkyl acetate, it is possible to replace the above-
mentioned addition of diethyl phosphite on the alkenyl
acetate by Arbuzov reaction of triethyl phosphite with
bromoalkyl acetate (Scheme 2). We used this reaction for
the preparation of 2-methyl-acrylic acid 5-(diethoxy-
phosphoryl)-pentyl ester.
The third step of synthesis is an unblocking of the
hydroxyl group. Most often a solution of potassium
hydroxide with methanol at room temperature is used for
this cleavage. Indeed, the yield of reaction under these
conditions is low, around 40%. Boutevin et al. [19] carried
out the cleavage in the presence of 8 mol-% KOH in
methanol at 60 °C. After 18 h, they obtained quantitative
conversion. We carried out the reaction with a large excess
of potassium hydroxide in methanol. The mixture was
stirred under reflux for 2 days. However, after this time the
The Arbuzov reaction [28] is very well known. This type
of reaction is typically achieved by heating a phosphite in
the presence of an alkyl bromide or iodide, which is
believed to dissociate and attack in a nucleophilic reaction
the C–O bond. Although the reaction conditions almost
always involve high temperatures, self-rearrangements
utilizing only the phosphorus ester have been known to
occur at moderate temperatures applying a Lewis acid
catalyst. We carried out the reaction with bromoalkyl
acetate and an excess of triethyl phosphite under reflux for
16 h. After the reaction, the excess of triethyl phosphite
1
total disappearance of the H NMR singlet around 2 ppm
characteristic of CH3C(O) group was not observed. Only
Scheme 2
O
OC2H5
OC2H5
O
Br
O
O
P
P
O
+
O
O
OC2H5
KOH/CH3OH
Cl
O
O
O
O
O
O
O
P
O
HO
P
O
NEt3/CH2Cl2
123

Synthesis of methacrylate-functionalized phosphonates and phosphates
419
Scheme 3
HME, Aliquat 336
CH3CN, reflux
ONa
O
OH
Cl
n
OH
+
n
O
O
Cl
NEt3
O
O
pyridine
CH2Cl2
P
O
O
n = 3, 6, 8
O
O
P
O
n
O
O
was removed under vacuum. Following two steps, the
unblocking of hydroxyl group and the esterification, was
carried out applying the above-mentioned conditions.
The overall yield of this procedure is lower than that of
the previously mentioned addition of the phosphite to the
alkenyl acetate, only 77%; however, it was also well
reproducible with easier availability of initial halogenated
alcohols or acetates, which take this process to a sufficient
economic level.
methacrylates [32], which were phosphorylated in a sub-
sequent step (Scheme 3).
The first step is a phase-transfer catalyzed alkylation.
Curci et al. [32] described the reaction of potassium meth-
acrylate with chloro alcohols followed by an oxidation by
formation resulting in carboxylic acids. In this work, the
better available sodium methacrylate was used. The possi-
bility of polymerization was eliminated by stabilizing the
methacrylate by hydroquinone monomethylether. The
reaction was accomplished by using AliquatÒ 336 as a
phase-transfer catalyst. Because of the presence of large
amount of catalyst, the product had to be purified by column
chromatography applying the solvent mixture dichlorme-
thane:methanol (100:1). However, a small quantity of
catalyst was always present in the product (Fig. 1). Some
authors [11] have prepared the hydroxyalkyl methacrylates
by the methacrylation of alkanediol in the presence of
p-toluenesulfonic acid crystals and 2,6-di-tert-butyl-p-cre-
sol. In this approach, the presence of a large amount of
secondary product bis(methacryloyloxyalkane) has been
noticed.
Methacrylated phosphates
Phosphates are also a very important group of organo-
phosphorous compounds with the general chemical formula
R0-OP(O)(OR)2. Four oxygen atoms on the phosphorous
head can cause higher hydrophility of phosphates than
phosphonates. Esters of phosphonic acid are usually more
stable to hydrolysis than the corresponding phosphates,
because the P–C bond in phosphonic acid derivatives is
generally very stable towards oxidation or hydrolysis, so
that many reactions can be carried out on the organic part of
the molecule. However, compounds with electronegative
substituents on the a-carbon atom are considerably less
stable. Previously, only a few methods described the prep-
aration of methacrylated phosphates containing alkyl-chain
spacers. Pudovik et al. [29] realized the preparation of
dialkyl(methacryloylethylenglycol)phosphate by a two-step
reaction. In a first step, metharyloylglycol ester was pre-
pared by reaction of ethylene oxide with methacrylic acid,
which reacts in the second step with diethyl chlorophos-
phate. The yields were lower than 50%. In the other works
[30, 31], the authors prepared chloroalkyl phosphates [30],
which reacted with methacrylic acid or hydroxyalkyl- or
hydroxyaryl-methacrylate [31] by formation of methacry-
lated phosphates. The disadvantages of these approaches
are the following separation of the unreacted methacrylic
acid and difficult preparation of chloroalkyl phosphates
with long alkyl chains. We used a different reaction
procedure based on the synthesis of hydroxyalkyl
The second step is an esterification of 2-methyl-acrylic
acid hydroxy-alkyl ester. This reaction was previously
performed with diethyl chlorophosphate in ether and
(a)
(c)
(e)
(b+d)
b
CH3
d
a
O
OH
H2C
c
e
O
b
a
6
5
4
3
2
1
ppm
Fig. 1 1H NMR (CDCl3) spectrum of 2-methyl-acrylic acid 3-
hydroxy-propyl ester (a) before and (b) after purification
123

´
D. Francova, G. Kickelbick
420
triethylamine [29]. We carried out the reaction in dichlo-
romethane with triethylamine. Under these conditions, the
reaction kinetic was very slow. It is known that the ester-
ification accomplished by organo-chlorides with hydrogen
in a-position of the carboxyl group forms ketene, which
easily reacts with the alcohol by formation of an ester, as in
the case of the above-mentioned methacrylation in the
synthesis of 2-methyl-acrylic acid hydroxy-alkyl ester by
methacryloyl chloride. For this reaction, diethyl chloro-
phosphate was used. In this case, pyridine is often used,
because pyridine is able to create a very reactive inter-
mediate, which in the presence of alcohol easily forms the
respective ester. Therefore, also pyridine was added to the
reaction mixture. The completeness of the reaction was
thermal polymerization of the methacrylate group. The
basic hydrolysis [35, 36] also requires drastic conditions
and is not too effective for the presented system because of
the possible cleavage of the ester bond. Rabinowitz [37]
has shown that bis(trimethylsilyl) phosphonates, prepared
by the action of chlorotrimethylsilane, hydrolyze to phos-
phonic acids on contact with water at room temperature.
However, this dealkylation requires long reaction times and
leads to low yields. McKenna et al. [38] have replaced the
chlorotrimethylsilane by bromotrimethylsilane, which is
more reactive. The formed trimethylsilyl phosphonates
were afterwards hydrolyzed with water. Some authors [19,
39] have proposed the cleavage by sodium iodide, which
was realized in anhydrous acetone under reflux. We applied
the cleavage method described by McKenna et al. [38]
using bromotrimethylsilane followed by methanolysis
(Scheme 4).
1
confirmed by IR and H NMR. The IR spectrum of the
methacrylated phosphate as well as the above-mentioned
methacrylated phosphonates showed ester carbonyl
1
absorption at 1,716 cm-1. H NMR revealed the disap-
This method enables performing the reaction under
mild conditions in a short time. The silylation of phos-
phonic esters is very often the method used for the
cleavage mainly for its mild conditions. However, this
method is not suitable for the preparation of monoacid,
because a mixture of monoacid and diacid is obtained after
methanolysis, which is difficult to separate. The advantage
of this method is also high effectivity and selectivity for
cleavage of the ester bonds with a high overall yield of
95%. The results of the synthetic work are summarized in
Table 1.
pearance of the triplet at 3.6 ppm of the CH2 protons in a-
position of the hydroxyl group.
Hydrolysis of methacrylated phosphonates
and phosphates
There are several methods for the hydrolysis of the phos-
phonic and phosphoric esters under acid and also basic
conditions. The acid hydrolysis exploiting the hydracides
[33, 34] requires quite high temperature, which can lead to
Scheme 4
Si
O
O
ethylacetat
O
P O
O
Br Si
+
O
P O
CH2Cl
O
n
O
n
O
O
Si
O
O
CH3OH
25 °C
O
OH
P
O
O
n
OH
Table 1 Summarizing table of
the results of the synthetic work
Compound
Overall yield (%)
Reference
a
2-Methyl-acrylic acid 3-(diethoxy-phosphoryl)-propyl ester
2-Methyl-acrylic acid 5-(diethoxy-phosphoryl)-pentyl ester
2-Methyl-acrylic acid 11-(diethoxy-phosphoryl)-undecyl ester
2-Methyl-acrylic acid 11-phosphono-undecyl ester
88
77
86
82
43
38.5
42
40
This publication
Ref. [19]
This publication
a
2-Methyl-acrylic acid 3-(diethoxy-phosphoryloxy)-propyl ester
2-Methyl-acrylic acid 6-(diethoxy-phosphoryloxy)-hexyl ester
2-Methyl-acrylic acid 8-(diethoxy-phosphoryloxy)-octyl ester
2-Methyl-acrylic acid 8-phosphonooxy-octyl ester
This publication
This publication
a
a
Published in Japanese patents
123

Synthesis of methacrylate-functionalized phosphonates and phosphates
421
Self-assembly of the amphiphiles
forms, they shifted the equilibrium completely to the salt
form by increasing the pH to 10. They also showed that for
compounds bearing fixed polar heads and hydrophobic
tails, under constant temperature, an increase in ionic
strength reduces the electrostatic repulsion between the
anionic polar heads, thereby favoring aggregation and
lowering of the CMC. Petrov et al. [45] showed that
poly(ethylene glycol) phosphates predominately form
micelles. They investigated the influence of the length of
(OCH2CH2)n chains on the micelle formation in aqueous
solution of phosphate esters of ethoxylated alkanol. The
optimal value of n was found to be three. They also found
that the length of (OCH2CH2)n chain influences the
hydrophilic–lyophilic balance and the micelle sizes of the
surfactants. In the latter work, the CMC of esters and acids
was determined in pure water at 25 °C. During the micelle
formation, some physic-chemical properties (e.g. electrical
conductivity, surface tension, osmotic pressure, turbidity,
etc.) are markedly changed.
The prepared organophosphates and organophosphonates
present typical structures of amphiphilic molecules. They
contain a polar hydrophilic head group and long hydro-
phobic tails. Therefore, these systems should show some
kind of self-aggregation behavior in aqueous solutions.
Phosphorylated molecules with long alkyl chains are well
known from biology as phospholipids [40]. The synthe-
sized systems present an additional polymerizable
functionality at the other chain end. We investigated their
self-aggregation behavior applying DLS. Phosphate end-
group-modified molecules are already known in literature
for their self-aggregation behavior. However, the known
examples describe only the systems with the posphorous
polar head and various hydrophobic tails without any
polymerizable end group such as hydroxyalkyl [41] or
(a-hydroxyalkyl)phosphorus surfactants [42], polyprenyl
phosphates [43] or poly(propylene glycol)phosphates [44].
Only a few investigations on the self-assembly behavior
of phosphates can be found in literature. Arigai et al. [43]
showed that alkyl phosphates with long alkyl chains pre-
dominately form monolayers. The monolayer properties of
some single-chain polyprenyl phosphates were investigated
at the air–water interface. Various pH conditions depen-
dence revealed the influence of pKa to a stability of the
phosphates as both monolayer and bilayer states. In addi-
tion, the ion effect on the stability of the monolayer was
investigated. The addition of magnesium ions or of a small
amount of calcium ions significantly improved mechanical
stability of the monolayer against collapse. In contrast, the
presence of large amounts of calcium or lanthanum ions
induced collapse of the monolayers. Sodium ions showed
only a weak effect on the stabilization of the monolayer.
Burn et al. [42] showed that a-hydroxyalkyl phosphonic
acids in dependence on the length of alkyl chain form
monolayers at the air/water interface; however, their
ammonium salts create micelles in aqueous solution. The
CMCs were determined by tensiometry. Because these
a-hydroxyalkyl phosphonic acid salts exist in aqueous
solution as an equilibrium between the acid and the salt
We used DLS measurements at room temperature to
estimate the CMC. For this purpose, we prepared several
samples with different concentrations in the range of
0.1 9 10-n–0.1 9 10-n-1 mol/L (n = 0, 1, 2, 3, 4) with
the difference in concentrations 0.1 9 10-n-1. The values
around the CMC were remeasured more precisely. The
samples slowly graded from highly turbid to almost clear
solution. Before the measurements, samples were briefly
sonicated in an ultrasound bath and left to stand for 20 min
to equilibrate the systems after sonication. We found
the CMC to be 0.033, 0.025, 0.040 and 0.036 mol/L
for 2-methyl-acrylic acid 11-phosphono-undecyl ester,
2-methyl-acrylic acid 11-(diethoxy-phosphoryl)-undecyl
ester, 2-methyl-acrylic acid 8-phosphonooxy-octyl ester
and 2-methyl-acrylic acid 8-(diethoxy-phosphoryloxy)-
octyl ester, respectively. All these samples were turbid.
DLS measurements of phosphonic acid and ester showed
two peaks (Fig. 2). The first one indicates the formation of
micelles. The second peak probably corresponds to
aggregates formed. 2-Methyl-acrylic acid 11-(diethoxy-
phosphoryl)-undecyl ester exhibits mainly the formation of
aggregates, so there is probably an absence of micellization
1,20
1,00
0,80
0,60
0,40
0,20
0,00
Fig. 2 DLS measurements of
(a) phosphonic acid
(2-methyl-acrylic acid
1,20
1,00
0,80
0,60
0,40
0,20
0,00
11-phosphono-undecyl ester)
and ester (2-methyl-acrylic acid
11-(diethoxy-phosphoryl)-
undecyl ester), (b) phosphoric
acid (2-methyl-acrylic acid
8-phosphonooxy-octyl ester)
and ester (2-methyl-acrylic acid
8-(diethoxy-phosphoryloxy)-
octyl ester)
0
1
10
100
1000
10000
0
1
10
100
radius (nm)
phosphoric ester
1000
10000 100000
radius (nm)
phosphonic ester
phosphonic acid
phosphoric acid
123

´
D. Francova, G. Kickelbick
422
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In this work, the synthesis of polymerizable phosphonates
and phosphates with amphiphilic character has been
described. Two different approaches for preparation of
these phosphonates have been suggested with respect to the
availability of initial products. High overall yields of 77–
88% were obtained by both methods. Two-step reactions
based on the phase-transfer catalyzed alkylation followed
by phosphorylation have been used for the preparation of
phosphates with overall yields of 39–43%. Hydrolysis of
the obtained esters by reaction of the alkyl-esters with
bromotrimethylsilane followed by methanolysis was car-
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of organophosphorous monomers was investigated. The
absence of micellization for 2-methyl-acrylic acid 11-(di-
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