Unsaturated polyphosphoesters via acyclic diene metathesis polymerization

Article abstract of DOI:10.1021/ma301508s

A powerful methodology for the synthesis of unsaturated polyphosphoesters (UPPEs) relying on acyclic diene metathesis (ADMET) polymerization is described. A facile two-step protocol gives fast access to structurally versatile and potentially degradable an

Full text of DOI:10.1021/ma301508s

Article
pubs.acs.org/Macromolecules
Unsaturated Polyphosphoesters via Acyclic Diene Metathesis
Polymerization
Filippo Marsico, Manfred Wagner, Katharina Landfester, and Frederik R. Wurm*
Max Planck Institut fur Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
̈
S
* Supporting Information
ABSTRACT: A powerful methodology for the synthesis of unsaturated polyphosphoesters (UPPEs) relying on acyclic diene
metathesis (ADMET) polymerization is described. A facile two-step protocol gives fast access to structurally versatile and
potentially degradable and biocompatible materials. For the first time this allows to control the microstructure of either backbone
and/or side chains of polyphosphoesters. Four different monomers are polymerized under different conditions to yield UPPEs
with molecular weights ranging from 7000 up to 50 000 g mol−1 with reasonable polydispersity. The unsaturated and saturated
polyphosphoesters are characterized in detail with various techniques. A major benefit of the UPPEs is revealed by differential
scanning calorimetry proving the control over thermal properties with tunable melting or glass transition temperatures for the
different saturated and unsaturated PPEs which is an important feature for future applications. This unique combination of the
benefits of metathesis polymerization and phosphorus chemistry is a highly versatile system for materials in many applications
ranging from adhesives to biomaterials.
and good tissue compatibility.10,11 The treatment of bone
defects could benefit from biocompatible and degradable
INTRODUCTION
Biodegradable polymers have received tremendous interest in
■
materials, which also assist in bone regeneration,12 and could
be a valid substitute to the widely used poly(methyl
methacrylate).13 Aliphatic polyesters such as poly(ε-caprolac-
tone) (PCL), poly(lactic acid) (PLA), poly(glycolic acid)
(PGA), and similar polymers are generally considered useful for
biomedical applications because of their favorable biocompat-
ibility and biodegradability.14−16 Their hydrophobicity and slow
degradation rate, however, may not be ideal for some
applications, but could be tuned by copolymerization
combining the advantages of aliphatic polyesters and PPEs.17,18
In the early 1970s, seminal works carried out by Penczek and
co-workers establishing the basis for the synthesis and the
potential biological application for a series of PPEs.19,20 These
polymers can be synthesized by polycondensation, trans-
esterification, or ring-opening polymerization (ROP) of
strained cyclic phosphates.4,21 Polycondensation is probably
the most used method for the preparation of PPEs due to
recent decades.1 Used for the development of novel materials in
the medical field of modern biotechnology or tissue engineer-
ing, most of them are based on conventional polyesters such as
polylactide or similar.2 However, a major drawback is the
restriction to a few monomer systems that results often in the
need of polymer modifications that are demanding multistep
approaches. In contrast, poly(phosphoester)s (PPEs), which
were earlier used as flame-retardant materials, are potentially
degradable and biocompatible polymers with repeating
phosphoester bonds along the backbone comparable to
biomacromolecules such as nucleic and teichoic acids.3,4 The
chemical versatility of the monomeric phosphate allows the
design of functional materials with tunable and complex
architectures and many different properties for drug delivery,5
gene delivery,6 pH/thermoresponsive materials,7,8 and tissue
engineering,9 of which the latter is particularly appealing for
biomedical applications. Regenerative medicine requires
scaffolds with tunable properties for tissue engineering
applications, and unsaturated polyphosphoesters (UPPEs)
with the phosphates being capable of binding calcium
phosphates are advantageous in terms of cytocompatibility
Received: July 19, 2012
Revised: September 25, 2012
Published: October 16, 2012
© 2012 American Chemical Society
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readily available monomers. However, in an early work, Vogt
and Balasubramanian have already reported that the conven-
tional polycondensation route is plagued by side reactions that
prevent the formation of polymers with molecular weights
higher than ca. 1000 g mol−1.22,23 Penczek and co-workers have
reported that the transesterification route yields polymers with
molecular weights higher than 10 000 g mol−1.24,25 The second
approach to PPEs is ROP that has been studied extensively for
cyclic phosphate monomers in bulk with enzymatic catalysis,26
or via cationic,27 anionic, or coordinative polymerization.28
Typical problems in cationic polymerization is that it produces
exclusively colored products with low molecular weights, while
triisobutyl aluminum is very efficient for catalyzing ROP to
obtain homo or random copolymers.4 Stannous octoate, a
widely used catalyst for the polymerization of cyclic esters, also
for the polymerization of five-membered phosphates.29 Typical
problems here are low molecular weight materials, the need of
high-purity monomers and the absence of water. Also, varying,
but low monomer conversions can be problematic (usually ca.
70%) and the materials show polydispersities around 1.50 or
lower in some cases.
throughout the backbone.37−39 To the best of our knowledge,
to date ADMET has not been applied to the synthesis of
(U)PPEs. As ADMET directly produces the unsaturated
polyester which are very important materials for coating
etc.because they can be UV-cured in a subsequent step
this is a very promising approach. Through ADMET, it is
possible to access precisely functionalized UPPEs with the
phosphate groups forming the polymer backbone. We believe
that these materials find many applications in especially metal
coatings or adhesives due to the high affinity of phosphates to
metals and, in addition, with the potential degradability are also
very attractive candidates for tissue engineering applications.
This is the first report on the ADMET approach to unsaturated
and saturated PPEs with a variable backbone which cannot be
prepared by ROP or other approaches.
RESULTS AND DISCUSSION
■
Monomer Synthesis. The monomers investigated in this
study were synthesized using commercially available phenyl
dichlorophosphate 1 which was esterified with the respective
alcohol in the presence of a base, pyridine, as described in the
following representative procedure (Scheme 2) for the
The acyclic diene metathesis polymerization (ADMET)30 is
a quantitative reaction tolerating many functional groups and
yields only the desired linear polymer and ethylene as a
byproduct. ADMET should be a perfect approach for the
synthesis of linear UPPEs. ADMET provides tools for accessing
linear polymeric structures in an efficient way from versatile
starting materials,31 which is in the case of PPEs, POCl3
(Scheme 1).
Scheme 2. General Protocol for the Synthesis of Phosphate
Monomers for ADMET
Scheme 1. ADMET Reaction, Ruthenium-Based Olefin
Metathesis Catalysts Used and Monomers Synthesized in
This Study
compounds 2a−d. The monomers are colorless liquids at
room temperature and can be stored at room temperature over
a period of (at least) several months. In contrast, the five- and
six-membered cyclic phosphates which are used in ROP are
sensitive monomers, and special precautions have to be
followed in handling these monomers, during the preparation,
the purification (generally by distillation), and especially the
conduction of the ROP. Their sensitivity easily quenches the
polymerization or unwanted initiation by water can occur. For
the liability of these cyclic compounds, most of the ROPs are
carried out on rather simple five membered, ethylene glycol-
bridged cyclic phosphates and subsequent postpolymerization
modification reactions are carried out. The ADMET approach
opens a great toolbox of a tremendous variety of substrates
which are more stable and easily available from POCl3.
ADMET Polycondensation. Motivated by the high
functional group tolerance of the Grubbs-type catalysts, we
investigated the influence of different catalysts on the molecular
weight and the polydispersity for the ADMET polymerizations
of the monomers 2a−d (Grubbs first generation (C1), Grubbs
second generation (C2), and Grubbs−Hoveyda first generation
(C3)) in the bulk with stirring at different temperatures (see
below). Since the monomers described herein are liquids, a
bulk polymerization is feasible and maximizing of the molar
concentration of the olefin and appropriate shifting of the
reaction equilibrium can be obtained when solvent is omitted.
Table 1 lists the results of the polymerizations.
Wagener’s group has explored the use of this polymerization
technique to elegantly synthesize precision polyethylene
containing functional groups such as halogens,32 polyolefins
targeted for biological applications,33 or silicon-containing
materials.34 More recently Meier and co-workers has broadened
the applications of this technique by preparing functional
hyperbranched materials through the metathesis of acyclic
triene monomers.35,36 This approach has led to a wide range of
unsaturated and saturated polymers bearing different function-
alities with the possibility to modify the polyolefin architectures
by placing precise functional groups phosphorus containing
The first reactions were carried out at 40 °C; however, it was
observed that the temperature was not high enough to activate
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Table 1. Conditions for the ADMET Polycondensation (General Representative Procedure) of 2a−d and Molecular Weight
Data of the Resulting Polymers
a
a
a
a
run
monomer
catalyst
catalyst [mol %]
temp[°C]
Mw [g/mol]
Mn [g/mol]
Mw /Mn
1
2
3
4
5
6
7
8
9
2a
C1
C2
C3
C1
C1
C3
C1
C3
C1
C2
C2
C3
C1
C2
C1
C2
C1
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
0.2
1.3
1.3
0.6
0.6
0.3
0.3
0.6
60
60
60
80
60
60
60
60
60
40
60
60
60
60
60
60
60
−
−
−
−
−
−
−
−
−
−
2a
2a
2a
−
−
2b
2b
2c
14 500
14 000
19 300
17 000
57 300
7200
7700
6000
10 000
8700
38 000
5050
26 800
23 600
32 400
22 700
20 200
22 700
6100
1.88
2.33
1.93
1.95
1.50
1.42
1.83
1.45
1.68
2.20
1.63
2.20
2.13
2c
2d
2d
2d
2d
2d
2d
2d
2d
2d, 2c
b
10
11
12
13
14
15
16
43 200
34 200
54 700
50 000
33 000
50 000
c
17
13 000
a
b
In g mol−1, determined by gel permeation chromatography (GPC) in THF vs polystyrene standards. The monomer (100 mg) and Grubbs’ first
c
generation catalyst (0.2 mol %) were dissolved in CH2Cl2 (2 mL). Random copolymer 8 between 2c and 2d in ratio 1:1.
the reaction efficiently, and sometimes unreacted monomer was
recovered. Therefore, the polymerization temperature was
raised to 60 °C, where upon a sudden color change from
purple to red (using C1 with monomer 2d), evolution of
ethylene, and a quick increase in the viscosity of the reaction
mixture was observed (Scheme 3).
coordinating oxygen atom to the reactive double bond was
increased just by one methylene unit (monomer 2b),
polycondensation results improved. After the catalyst, the
mixture immediately turned red, with a gradual increase of the
viscosity to give polymers with Mn’s of 8000 g mol−1 (runs 5,6).
The polycondensation of 2c proceeded in a fashion similar to
that of 2b. The polymeric materials isolated were in the range
of 8000−10000 (Mn) g mol−1and were readily soluble in THF.
Figure 1 shows a representative SEC elugram of a polymer
from monomer 2d (run 13) synthesized in bulk, in comparison
to the diluted synthesis performed in solution (run 10). The
monomer 2d was injected also to the GPC and it can be
observed, that the oligomers from solution polymerization still
contain a monomer fraction (eluating at 30.4 mL). Interest-
ingly, in the oligomer, there is a shoulder to higher elution
times (ca. 31−32 mL), indicating the presence of cyclic
monomer which should elute later than the linear counterpart.
The main peaks in the MALDI section of Figure 1 correspond
to the oligomers, ranging from dimers to pentamers (for
example: the peak at 995 g mol−1 in Figure 1 corresponds to
the molecular ion of [2M + K]+]) observed in the elugram of
the oligomer (run 10), while the neighboring peaks exhibit an
interval of 14 g mol−1 (methylene units) which is most likely
attributed to Ruthenium-hydride formation, resulting in double
bond isomerizations, during ADMET in the particular
conditions (in solution) using catalyst C2.43,44 This isomer-
ization was not observed in the MALDI spectrum of a relatively
low molecular weight sample of polymer 4 (Mn= 3000 g mol−1;
compare with Figure S29 in the Supporting Information). This
is reasonable as isomerization would produce a phosphoric acid
allyl ester that cannot undergo further metathesis (see above)
resulting in a precise polymer.
Scheme 3. ADMET Polymerization of a Phosphate
Monomer 2a−d
Polydispersities of the polymers are in agreement with the
theory concerning the Carothers equation that predicts the
most probable distribution of 2 for a linear polycondensation,
as conversion reaches 100%.40 Because of the increase in
viscosity after one/2 h the reaction temperature was gradually
raised to 80 °C to allow efficient mixing of the polymerization
mixture. After ca. 10 h at 80 °C the evolution of ethylene
ceased. The polymers were dissolved in dichloromethane and
precipitated into methanol or hexane. For monomer 2a, no
polymeric materials were obtained and the monomer was
recovered in all the cases (runs 1−4). This is attributed to the
so-called “negative neighboring group effect”. Because of the
proximity of the coordinating ester, metathesis under
ruthenium catalysis is slow or even prevented due to
complexation of the heteroatom lone pair with the metal
center.41 This lack of reactivity could alternatively justified by
the formation of particular resting state of the carbene formed
with the allyl substrate possible via coordination to the
phosphate.42 This was also visible with the naked eye for
polymerization attempts of 2a, as the reaction mixture turned
brown immediately. As expected, when the distance of the
This systematic process allows the study of ideal models of
functionalized PPEs with precisely placed substituents and
simply by choosing the proper catalyst and monomer, in the
absence of solvent and under reduced pressure, leads to
quantitative yield of the desired polymer. In this regard, a
monomer bearing longer side chains was synthetized (2d). The
reactions of 2d proceed in the same manner as for the other
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Figure 1. GPC-elugram of polymer 6 (runs 10 (solution) and 13 (bulk)) vs polystyrene standards in THF (bottom). The dotted signal belongs to
the monomer 2d. The presence of oligomers can be clearly detected for low molecular weight 6 from run 10 and quantified by MALDI−MS (top).
monomers, in this case observing a quick viscosity increase.
After a screening on different parameters as reported in Table
1, the optimum conditions for the polymerization of 2d was
found to be at 60 °C, 0.3 mol % of Grubbs’ first generation
catalyst, and for 10−12 h polymerization time (Mw = 57 300
Mn = 38 000 PDI 1.5). 2d was also investigated in a one-pot
copolymerization with 2c in ratio 1:1 following the standard
procedure, leading to a sticky gum (Mw = 13 000) soluble in
CH2Cl2 or THF (run 17). UPPEs with different molecular
weights have been prepared following the ADMET approach.
The resulting polymers are rich in trans olefins due to the
ADMET mechanism, since the stereochemistry is controlled
thermodynamically due to the equilibrium nature of the
polymerization.45 Because the results for ADMET are highly
dependent on the catalytic system, only ruthenium-based
catalysts were selected, free of Lewis acids, that favor metathesis
chemistry over vinyl addition,46 and are only reactive toward
olefins.47 Figure 2 shows the 1H NMR spectra of monomer 2d
(bottom) and the respective polymer (middle) proving the
complete disappearance of the terminal double bonds (5.8 and
4.9 ppm) and the formation of internal double bonds (5.4
ppm). A zoom into the region of the terminal double bonds
also allows the determination of the molecular weight of the
polymers (see below). In a following step, a saturated PPE (7)
has been synthesized from 6 via catalytic hydrogenation. In an
ideal case the phosphates are separated by 20 carbon centers,
however the observed isomerization effect introduces some
irregularities which can be overcome by the use of monomer 2b
(compare Figure 2, top spectrum). This broadens the range of
accessible materials by this synthetic strategy from UPPEs in
order to prepare saturated PPEs. Metathesis chemistry, in fact,
is giving promising results in the preparation of degradable
materials from renewable resources.48 Polymer 7 can be
regarded as a degradable polyethylene with predetermined
1
breaking points inside the backbone. H NMR and 13C NMR
spectroscopy proves complete reduction of all double bonds
(Figure 2).
In addition, GPC results prove that the phosphate linkages
are stable under the hydrogenation conditions (Pd/C, H2, 8
bar) and fully saturated PPEs can be generated with different
materials properties (see below). The molecular weight of the
saturated polymer 7 (54 000 g mol−1, PDI 1.90) estimated by
GPC was in agreement with the starting material. Like the
other unsaturated polymers 31P NMR measurements revealed
for 7 only a single peak around −7 ppm, excluding the presence
of disubstituted or monosubstituted phosphate in the material
isolated (compare Figures S15, S18, and S21 in the Supporting
Information). For all polymers, molecular weights were
obtained from GPC in THF against polystyrene standards. In
addition, ADMET produces only linear polymers that possess
terminal double bonds as the respective end groups which are
1
accessible for further reactions. With high resolution H NMR
spectroscopy these can be used to calculate an absolute
molecular weight. For a low molecular weight PPE this
spectrum is shown in Figure 3. By integration of the terminal
olefinic signals Mn’s of 40 000, 60 000, and 140 000 have been
calculated respectively for the polymers 4, 5, and 6 (entries 5, 7,
and 9 of Table 1). For Mn’s higher than 50 000 g/mol, the
1
Figure 2. H NMR investigation (700 MHz in CDCl3 at 298.3 K)
showing the aromatic and olefinic region of the spectra of monomer,
polymer and hydrogenated polymer (2d, 6 and 7).
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1
Figure 3. H NMR spectrum (700 MHz) in CDCl3 at 298.3 K showing the aromatic and olefinic signals of a polymer 6 4000 g mol−1 sample
calculated by NMR.
method is limited of course, due to increase in the noise ratio
and possible isomerization of the terminal end-group resulting
in large errors.
The resonances labeled belong respectively to the phenyl
pendant group (7.2 ppm), the terminal groups (a, 5.0 ppm; b,
4.9 ppm; e, 5.8 ppm) and internal (c, 5.38 ppm; d, 5.34 ppm)
1
olefinic protons. H−1H COSY (see Supporting Information
Figure S22) of polymer 6 (Mn 9000 g mol−1) further proves the
presence of terminal double bond signals, which disappear after
hydrogenation.
Thermal Characterization. The UPPEs synthesized in this
study range from sticky gums to rubbers, which are ready
soluble in common organic solvents such as CHCl3, CH2Cl2,
and toluene. The flexible P−O−C groups in the backbone
commonly result in PPEs with low glass transitions (−40
°C).9,49 Interestingly it has been observed that the glass
Figure 4. DSC thermograms of 6 and 7.
transition of a poly(lactide-co-ethylphosphate) copolymer
depends inversely on the weight percentage of phosphoester
segment in the copolymer.5 The Fox equation for these
Summary. This study presents the first report on an
ADMET approach to synthetic (U)PPEs allowing easy
variation of the polymer backbone and side chains by
polymeric systems estimated the Tg at −30 °C for a PPE
homopolymer, which is consistent with the role of an internal
combining the advantages of metathesis with the versatility of
plasticizer of the phosphoester monomer itself. The thermal
phosphorus chemistry. A variable approach to several
unsaturated poly(phosphate)s is reported based on bulk
polymerization using different Grubbs catalysts. The molecular
weights vary for the different monomers and catalysts applied
but in all cases high molecular weight polymers were obtained
and thus empirically the molecular weight can be adjusted.
stability of the polymers 4, 5, 6, and 7 was examined by thermal
gravimetric analysis (TGA) while the glass transition temper-
atures (Tg) and the melting points (Tm) were determined by
differential scanning calorimetry (DSC) under nitrogen (Figure
4). The materials synthesized showed the typical low
temperature glass transitions of PPEs, with a relevant
Further, the molecular weights of the resulting PPEs are much
contribution of the olefinic double bonds to the polymer
higher compared to many literature protocols, confirming the
microstructure for the polymers 4, 5, and 6 shifting the Tg to
advantages by using ADMET as an ideal synthetic strategy for
−30 to −70 °C. In addition, the melting temperatures of the
polymers 6 and 7 (50 000 g mol−1) change as the unsaturated
backbone is hydrogenated. Even polymer 6 exhibits a melting
temperature at −7 °C upon heating and cooling, while the
equivalent hydrogenated polymer 7 shows melting at 44−45 °C
due to the disappearance of the double bonds which act as a
defect during the crystallization of the polymer(Figure 4). All
the other unsaturated polymers exhibit different glass
transitions at −32 °C for 4 (14 000 g mol−1) and −53 °C
for 5 (20 000 g mol−1), without observing a melting peak.
(U)PPEs.
Another major advantage of this approach is the possible
variation of the PPE backbone which is not possible by ring-
opening polymerization where usually ethylene-bridged cyclic
phosphates are applied. We believe that this procedure can be
easily scaled up and is very promising even for industrial
application as unsaturated polyesters are a very important
market. With phosphate linkages along the unsaturated
backbone many properties of these unsaturated polyesters
will be altered, which is currently under investigation in our
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over sodium sulfate, filtered, concentrated in vacuum, and purified by
column chromatography over silica using dichloromethane as an
eluent to give a clear colorless liquid. The structures were determined
by 1H NMR, 13C NMR, 31P NMR spectroscopies as well as
electrospray ionization mass spectrometry (ESI−MS). No impurities
were detected in all cases.
Representative Procedure for ADMET Bulk Polymerization.
In a glass Schlenk tube, the monomer and the appropriate catalyst (0.3
mol %) were mixed under an argon atmosphere. Under reduced
pressure to remove ethylene gas evolving during the metathesis
reaction, the temperature was raised up to 60 °C with stirring for 1−2
h and then at 80 °C for additional 8−10 h. The reaction was allowed
to cool at room temperature. The polymers were then dissolved in
CH2Cl2, treated with activated charcoal and filtered over Celite. They
were isolated then after precipitation from methylene chloride into
methanol or hexane, when requested, and dried.
group. These UPPEs are also interesting candidates for
biomedical applications and as potential tissue engineering
scaffold materials but also in materials science and concerning
their flame-retardant properties. Currently, we are focusing on
broadening the spectrum of PPEs synthesized by ADMET to
more sophisticated polymer architectures, tailoring physical
properties and introducing bioactive moieties.
EXPERIMENTAL SECTION
■
Chemicals. All chemicals were purchased from Sigma-Aldrich and
used as received if not otherwise mentioned. Dichloromethane and
pyridine were dried and stored under argon. Grubbs catalyst first
generation, Grubbs catalyst second generation, Hoveyda−Grubbs
catalyst first generation were purchased from Sigma-Aldrich and stored
under argon.
Procedure for ADMET Solution Polymerization. The mono-
mer (100 mg) and Grubbs’ first generation catalyst (0.2 mol %) were
dissolved in CH2Cl2 (2 mL) for polymerization of 2d under argon and
stirred at 40 °C for 12 h. The same procedure as described above was
used to isolate the polymer.
Procedure for Catalytic Hydrogenation. A 200 mg sample of
the polymer 3d, 5 mL of toluene, and 10 mg of 5% Pd/C catalyst were
charged into a reactor and flushed with nitrogen. Hydrogenation was
then performed with vigorous stirring under a hydrogen pressure of 8
bar at room temperature for 12 h. The solution was filtered over Celite
and the solid polymer isolated after solvent evaporation in quantitative
yield.
Methods. Gel-permeation chromatography (GPC) measurements
were carried out in DMF or THF, with samples of the concentration
of 1 g L−1. Sample injection was performed by a 717 plus auto sampler
(Waters) at 30 °C (THF). Flow was 1 mL min−1. In DMF, three
GRAM columns (PSS), 300 × 80 mm, 10 μm particle size with
respective pore sizes of 106, 104, and 103 Å were employed. In THF,
three SDV columns (PSS) with the dimensions 300 × 80 mm, 10 μm
particle size and pore sizes of 106, 104, and 500 Å were employed.
Detection was accomplished with DRI Shodex RI-101 detector (ERC)
and UV−vis S-3702 detector (Soma). Calibration was carried out
using polystyrene standards provided by Polymer Standards Service.
1
All the NMR experiments were done with a 5 mm BBI H/X z-
Synthesis of Phenyl Diallyl Phosphate (2a). Following the
general procedure described above and using allyl alcohol, 2a was
obtained as a clear oil with a yield of 75% after column
chromatography over silica using as eluent dichloromethane (Rf:
0.3). 1H NMR, δ (ppm): 7.31(t, J = 7.7 Hz = 2H), 7.21(d, J = 7.7 Hz,
2H), 7.16(t, J = 7.7 Hz, 1H), 5.94−5.89 (ddt, J = 18 Hz, J = 10.5 Hz, J
= 5.6 Hz, 2H), 5.35 (ddt, J = 18 Hz, J = 1.4 Hz, 2H), 5.23 (d, J = 10.5
Hz, 2H), 4.65−4.59 (m, 4H). 13C NMR, δ (ppm): 150.70, 150.66,
132.18, 132.14, 129.77, 125.17, 120.10, 120.08, 118.64, 68.86, 68.83.
31P NMR, δ (ppm): −6.20. ESI−MS: m/z 277.05 [M + Na]+, 531.14
[2M + Na]+ (calcd for C12H15O4P: 254.07).
gradient on the 700 MHz spectrometer with a Bruker Avance III
system. For 1H NMR spectra, 128 transients were used with an 11 μs
long 90° pulse and a 12600 Hz spectral width together with a recycling
delay of 5 s. The 13C NMR (176 MHz) and 31P NMR (283 MHz)
measurements were obtained with an 1H powergate decoupling
method using 30° degree flip angle, which had a 14.5 μs long 90° pulse
for carbon and an 25.5 μs long 90° pulse for phosphorus. The spectral
widths were 41,660 Hz (236 ppm) for 13C and 56,818 Hz (200 ppm)
for 31P, both nuclei with a relaxation delay of 2s. The proton, carbon
and phosphorus spectra were measured in CDCl3 at 298.3 K and the
spectra were referenced as follows: for the residual CHCl3 at δ (1H) =
7.26 ppm, CDCl3 δ (13C triplett) = 77.0 ppm, and triphenylphosphine
(TPP) δ (31P) = −6 ppm. The assignment was accomplished by 1H,1H
COSY (correlated spectroscopy) 2D method. The spectroscopic
widths of the homonuclear 2D COSY experiments were typically
14000 Hz in both dimension (f1 and f2) and the relaxation delay 1.2 s.
The temperature was kept at 298.3 K or and regulated by a standard
1H methanol NMR sample using the topspin 2.1 software (Bruker).
Matrix-assisted laser desorption and ionization time-of-flight
(MALDI−ToF) measurements were obtained with a Shimadzu
Axima CFR MALDI−ToF mass spectrometer, equipped with a
nitrogen laser delivering 3 ns laser pulses at 337 nm. Dithranol (1,8,9-
tris-hydroxyanthracene) was used as a matrix. Samples were prepared
by dissolving the polymer in CHCl3 at a concentration of 10 g L−1. A
10 mL aliquot of this solution was added to 10 mL of a 10 g L−1 matrix
solution and 1 mL of a potassium trifluoroacetic acid (KTFA) solution
(0.1 M in methanol as cationization agent). A 1 mL aliquot of the
resulting mixture was applied to a multistage target to evaporate
CHCl3 and create a thin matrix/analyte film. The samples were
measured in positive ion- and in linear mode of the spectrometer.
The glass transition temperature was measured by differential
scanning calorimetry (DSC) on a Mettler Toledo DSC 823
calorimeter. Three scanning cycles of heating−cooling were performed
(in a N2 atmosphere 30 mL min−1) with a heating rate of 10 °C min−1.
Representative Procedure for Monomer Synthesis. To a
dried two-necked, 250 mL round-bottom flask 5 mL (3.55 g, 16.81
mmol) of 1 dissolved in 50 mL of dry CH2Cl2 with stirring was added
under an argon atmosphere. The solution was cooled to 0 °C and then
2.2 equiv of the appropriate alcohol and 2.2 equiv of pyridine were
added to the solution via syringe. The reaction was stirred overnight at
room temperature. The crude mixture was dissolved in diethyl ether
and washed twice with aqueous 10% HCl. The organic layer was dried
Synthesis of Phenyl Di(but-3-en-1-yl) Phosphate (2b).
Following the general procedure described above and using 3-buten-
1-ol, 2b was obtained as a clear oil with a yield of 70% after column
chromatography over silica using as eluent dichloromethane (Rf: 0.3).
1H NMR, δ (ppm): 7.33−7.31 (m, = 2H), 7.20 (d, J = 7.7 Hz, 2H),
7.16(t, J = 7.7 Hz, 1H), 5.79−5.73 (ddt, J = 16.8 Hz, J = 10 Hz, J = 3.5
Hz, 2H), 5.11 (ddt, J = 16.8 Hz, J = 1.4 Hz, 2H), 5.08 (d, J = 10 Hz,
2H), 4.20−4.13 (m, 4H), 2.44−2.42 (m, 4H). 13C NMR, δ (ppm):
150.69, 150.65, 133.12, 129.70, 125.05, 120.04, 120.01, 117.91, 67.54,
67.50, 34.60, 34.56. 31P NMR, δ (ppm): −6.40. ESI−MS: m/z 305.07
[M + Na]+, 587.18.30 [2M + Na]+ (calcd for C14H19O4P: 282.10).
Synthesis of Phenyl Di(hex-5-en-1-yl) Phosphate (2c).
Following the general procedure described above and using 5-hexen-
1-ol, 2c was obtained as a clear oil with a yield of 75% after column
chromatography over silica using as eluent dichloromethane (Rf: 0.4).
1H NMR, δ (ppm): 7.32 (t, J = 7.7 Hz = 2H), 7.21(d, J = 7.7 Hz, 2H),
7.16(t, J = 7 Hz, 1H), 5.79−5.73 (ddt, J = 16.8 Hz, J = 10.5 Hz, J = 3.5
Hz, 2H), 5.00−4.94 (ddt, J = 16.8 Hz, J = 1.4 Hz, 2H), 4.96−4.95 (m,
2H), 4.14 (m, 4H), 2.07−2.04 (m, 4H), 1.71−1.63 (m, 4H), 1.46 (q, J
= 7.7 Hz, 4H). 13C NMR δ (ppm): 150.89, 150.86, 138.29, 129.80,
125.08, 120.08, 115.05, 68.47, 68.43, 33.21, 29.74, 29.70, 24.74. 31P
NMR, δ (ppm): −6.11. ESI−MS: m/z 361.16 [M + Na]+, 699.30 [2M
+ Na]+, 1277.48 [3M + Na]+ (calcd for C18H27O4P: 338.16).
Synthesis of Phenyl Di(undec-10-en-1-yl) Phosphate (2d).
Following the general procedure described above and using 10-
undecen-1-ol, 2d was obtained as a clear oil with a yield of 80% after
column chromatography over silica using as eluent dichloromethane
(Rf: 0.5) .1H NMR, δ (ppm): 7.32 (t, J = 7.7 Hz = 2H), 7.21(d, J = 7.7
Hz, 2H), 7.16(t, J = 7.7 Hz, 1H), 5.83−5.77 (ddt, J = 16.8 Hz, J = 10
Hz, J = 3.5 Hz, 2H), 5.00−4.97 (ddt, J = 10 Hz, J = 3.5 Hz, J = 1.4 Hz,
2H), 4.93−4.91 (ddt, J = 10 Hz, J = 1.4 Hz, 2H),4.16−4.09 (m, 4H),
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2.04−2.01 (m, 2H), 1.69−1.65 (m, 4H), 1.39−1.32 (m, 8H), 1.26 (m,
18H). 13C NMR, δ (ppm): 150.98, 150.94, 139.29, 129.77, 125.02,
120.10, 114.27, 68.69, 68.66, 33.93, 30.37, 30.33, 29.55, 29.04. 31P
NMR, δ (ppm): −6.11. ESI−MS: m/z 501.33 [M + Na]+, 979.67 [2M
+ Na]+, 1458.00 [3M + Na]+ (Calcd for C28H47O4P: 478.32).
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Polymer 4. H NMR, δ (ppm): 7.32−7.30 (m, = 2H), 7.19−7.14
(m, 3H), 5.47−5.44 (m, 2H), 4.10−4.08 (m, 4H), 2.40−2.35 (m, 4H).
13C NMR, δ (ppm): 150.79, 150.75, 129.86, 128.18, 127.23, 125.23,
120.10, 120.08, 67.83, 67.80, 67.59, 33.64, 33.60. 31P NMR, δ (ppm):
−6.38.
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Polymer 5. 1H NMR, δ (ppm): 7.32−731 (m, 2H), 7.21−7.20(m,
2H), 7.16−7.14(m, 1H), 5.33 (m, 2H),4.13−4.11 (m, 4H), 1.97 (m,
4H), 1.68−1.65 (m, 4H), 1.42−1.39 (m, 4H).13C NMR, δ (ppm):
150.90, 150.87, 130.30, 129.82, 125.10, 120.10, 68.54, 68.50, 67.09,
53.58, 32.04, 29.81, 29.75, 28.41, 25.38. 31P NMR, δ (ppm): −6.12.
Polymer 6. 1H NMR, δ (ppm): 7.34−7.31 (m, 2H), 7.22−7.20 (m,
2H), 7.17−7.15(m, 1H), 5.41−5.34 (m, 2H), 4.15−4.09 (m, 4H),
2.02−1.96 (m, 4H), 1.69−1.65 (m, 4H), 1.38−1.21 (m, 24H). 13C
NMR, δ (ppm): 151.00, 150.96, 130.48, 129.80, 125.05, 120.14,
120.11, 68.73, 68.69, 32.77, 30.40, 30.36, 29.82, 29.62, 29.57, 29.33,
29.26, 25.53. 31P NMR, δ (ppm): −6.11.
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Polymer 7. 1H NMR, δ (ppm): 7.34−7.31 (m, 2H), 7.22−7.20 (m,
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1.36−1.20 (m, 36H). 13C NMR, δ (ppm): 151.01, 150.97, 129.79,
125.04, 120.14, 120.11, 68.73, 68.69, 66.00, 30.42, 30.36, 29.89, 29.87,
29.73, 29.67, 29.27, 25.54. 31P NMR, δ (ppm): −6.10.
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Polymer 8. 1H NMR, δ (ppm): 7.33−731 (m, 2H), 7.21−7.17(m,
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2.01−1.94 (m, 4H), 1.68−1.66 (m, 4H), 1.45−1.25 (m, 14H). 13C
NMR, δ (ppm): 150.99, 150.95, 131.28, 131.30, 130.47, 130.31,
129.81, 129.49, 125.04, 120.12, 120.10, 68.92, 68.89, 68.71, 68.68,
68.58, 68.54, 32.76, 32.73, 32.22, 32.06, 30.39, 30.35, 29.81, 29.75,
29.61, 29.56, 29.46, 29.32, 29.03, 28.32, 25.90, 25.54, 25.39 . 31P NMR,
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ASSOCIATED CONTENT
■
S
* Supporting Information
1H NMR, 13C NMR, and 31P NMR spectra for the monomers
(26) Wen, J.; Zhuo, R. X. Macromol. Rapid Commun. 1998, 19, 641−
642.
1
and polymers synthesized, H−1H COSY for polymer 6, and
(27) Oussadi, K.; Montembault, V.; Belbachir, M.; Fontaine, L. J.
MALDI−ToF spectrum of polymer 4.This material is available
Appl. Polym. Sci. 2011, 122, 891−897.
(28) Xiao, C. S.; Wang, Y. C.; Du, J. Z.; Chen, X. S.; Wang, J.
Macromolecules 2006, 39, 6825−6831.
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
(29) Wang, Y. C.; Tang, L. Y.; Sun, T. M.; Li, C. H.; Xiong, M. H.;
Wang, J. Biomacromolecules 2007, 9, 388−395.
(30) Wagener, K. B.; Boncella, J. M.; Nel, J. G. Macromolecules 1991,
24, 2649−2657.
■
*E-mail: wurm@mpip-mainz.mpg.de. Telephone:
+496131379502. Fax: +496131370330.
(31) Opper, K. L.; Wagener, K. B. J. Polym. Sci., Part A: Polym. Chem.
2011, 49, 821−831.
Notes
The authors declare no competing financial interest.
(32) Boz, E.; Wagener, K. B.; Ghosal, A.; Fu, R.; Alamo, R. G.
Macromolecules 2006, 39, 4437−4447.
ACKNOWLEDGMENTS
(33) Hopkins, T. E.; Wagener, K. B. Macromolecules 2004, 37, 1180−
1189.
■
F.M. acknowledges the International Max Planck Research
School for support. F.W. acknowledges the Alexander von
Humboldt foundation and the Max Planck Graduate Center for
support.
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