Macromolecules
Article
Figure 1. (a) Phosphonium polymer synthesis: (i) 1.1 equiv of trihexylphosphine, acetonitrile, 60 °C, 10 h; (ii) AIBN, dodecanthiol, anisole, 70 °C,
overnight. (b) Photograph of the synthesized polymer.
spectra were obtained on an Agilent 1100 LC/MSD trap with ESI and
APCI sources.
bounced back was measured. The experiment was performed 10 times,
and the ball was left at room temperature for 10 s between each test.
General Procedure for Rheology Assays. A TA AR1000 rhe-
ometer equipped with a Peltier temperature controller and a 20 mm
aluminum (plane−plane) geometry was used for creep recovery
experiments, and a 12 mm steel geometry was used for G′, E modulus,
and delta angle determination. All rheological measurements were per-
formed at 25 °C, and the viscosity data were reported at a frequency of
1 Hz. The samples were dried prior to the measurements.
Differential Scanning Calorimetry. Thermal transitions were
measured using a differential scanning calorimeter (Q100, TA
Instruments) at a heating rate of 20 °C/min and a cooling rate of
10 °C/min from −100 to 200 °C.
Synthesis of Trihexyl(4-vinylbenzyl)phosphonium Chloride
(1). Under nitrogen, 4-chloromethylstyrene (3.4 g, 22.2 mmol,
1 equiv) and trihexylphosphine (7.02 g, 24.4 mmol, 1.1 equiv) were
dissolved in 5 mL of acetonitrile. The mixture was stirred overnight
at 60 °C. The solvent and excess of starting material were then removed
under high vacuum overnight. The compound was used for the next
step without further purification. 8.6 g of product was isolated (yield:
88%). Rf: 0.5 (DCM/methanol, 95/5). 1H NMR (400 MHz, CDCl3):
0.86−0.9 (m, 9H), 1.24−1.47 (m, 24H), 2.38−2.45 (m, 6H), 4.29
(s, 1H), 4.33 (s, 1H), 5.29 (d, J = 18 Hz, 1H), 5.76 (d, J = 18 Hz 1H),
6.69 (dd, J = 8 and 18 Hz, 1H), 7.38−7.43 (m, J = 8 Hz, 4H). 13C
NMR (101 MHz, CDCl3): 13.7, 18.5, 19.0, 21.5, 22.1, 26.4, 26.8, 30.2,
30.4, 30.8, 114.5, 126.8, 128.2, 130.2, 135.7, 137.4. 31P NMR (161
MHz, CDCl3): 31.3. HRMS (ESI): [M − Cl]+ calcd 403.3494; found
403.3487.
X-ray Diffraction. Two sets of X-ray diffraction experiments were
performed. In one, specimens were prepared by drying a chloroform
solution of the assembly onto a curved glass substrate, and patterns
were recorded at ambient conditions using a line-focused X-ray camera
with a flat plate film cassette loaded with Kodak BioMax film.35
A
Synthesis of Poly(trihexyl(4-vinylbenzyl)phosphonium
chloride). (2). In a Shlenck tube, compound 1 (2.89 g, 6.6 mmol)
was dissolved in anisole (3 mL). The dodecanethiol (65 mg, 0.33
mmol, 0.05 equiv) and AIBN (1.6 mg, 0.01 mmol, 0.0015 equiv) were
then added. The mixture was stirred overnight at 70 °C. The reaction
was stopped by cooling the mixture to room temperature and exposing
it to oxygen. The polymer was precipitated in hexane and filtered.
2.44 g of polymer was obtained (yield: 84%). All NMR signals appear as
broad peak. 1H NMR (500 MHz, CDCl3): 0.84, 1.25, 1.43, 2.42, 6.41,
7.37. 13C NMR (126 MHz, CDCl3): 13.9, 18.7, 19.1, 21.7, 22.3, 30.2,
30.6, 31, 126.1−130.5. 31P NMR (161 MHz, CDCl3): 31.2. Size
exclusion chromatography (SEC) was performed with dichloro-
methane as the solvent at a flow rate of 1 mL/min as eluent through
an Agilent PLgel 3 μm Mixed-E 300 × 7.5 mm column. The molecular
weights were measured against poly(ethylene glycol) standards. SEC
studies gave a molecular weight: 60 000 g mol−1 (PDI: 1.83).
Synthesis of 15-Oxo-2,5,8,11,14-pentaoxaoctadecan-18-oic
Acid (6). Anhydrous pyridine (2 mL) was added first at 0 °C to
succinic anhydride (2 g, 20 mmol, 2.1 equiv). Tetraethylene gly-
colmonomethyl ether (2 g, 9.6 mmol, 1 equiv) was then added. The
reaction mixture was stirred for 4 h at room temperature. 20 mL of ice
cold 1 M HCl solution in water was added. The mixture was then
extracted 3 times with 50 mL of DCM, and the organic layer was
washed once with 20 mL of brine. The organic phase was dried with
Na2SO4, and the solvent was removed under reduced pressure. 2.76 g
of product was isolated after chromatography (95/5, DCM/methanol)
(yield: 93%). Rf: 0.36 (90/10, DCM/methanol). 1H NMR (400 MHz,
CDCl3): 2.66 (s, 4H), 3.38 (s, 3H), 3.55−3.57 (m, 2H), 3.64−3.71
(m, 12H), 4.24−4.27 (m, 2H). 13C NMR (101 MHz, CDCl3): 29.0,
29.3, 58.9, 63.8, 69.0, 70.4, 70.5, 70.6, 71.8, 172.2, 175.4. HRMS (ESI):
[M + Na]+ calcd 331.1369; found 331.1367.
second set of small-angle X-ray scattering (SAX) experiments were
realized with a H.I. Nanostar device (from Bruker) with point
collimation and wavelength of the radiation equal to λ = 1.5418 Å.
Experiments were performed under vacuum at room temperature, and
a 2D gas detector (HiStar, also from Bruker. 1024 × 1024 pixels with
100 μm pixel size) was used for recording the spectra. The sample-
to-detector distance was 25.5 cm. Each sample was placed in the window
of a metal cylinder inserted into a glass capillary with a diameter of 3 mm.
RESULTS AND DISCUSSION
■
In our system, we are interested in the solid-state polyelectrolyte−
surfactant complexes formed between a polystyrenylphospho-
nium and four different carboxylates. The polystyrenylphos-
phonium polymer, 2, was synthesized in two steps as shown in
Figure 1. The monomer 1 was obtained by reacting 4-chloro-
methylstyrene with an excess of trihexylphosphine in
acetonitrile at 60 °C for 10 h. The chlorophosphonium styrene
derivative was isolated as a white powder by removing the
remaining starting material under high vacuum (yield 88%).
Polymer 2 was obtained using AIBN as the free radical initiator
of 1 in anisole after 12 h. The Mw of 2 was controlled by
the addition of 5% dodecanthiol as a chain transfer agent.
Precipitation of the polymer in hexane gave 2 as a white
powder (yield 84%; Mw 60 000; PDI 1.8; mp = 110−120 °C).
The polymer is soluble in water, DMSO, DCM, and THF. As 1
is an ionic liquid monomer, the polymerization of ionic liquid
monomers is also of general interest,36−38 and recently, Long
et al. have reported new phosphonium triblock copolymers
using an ionic liquid monomer.39
General Procedure for Mixture Preparation. The polymer
(300 mg) was added to the corresponding carboxylic acid (1 equiv per
charge). The mixture was dissolved in organic solvent (DCM or THF)
and mixed to give a homogeneous mixture. The solvent was then
removed under high vacuum at 80 °C for 12 h.
General Procedure for Bounce Assays. A 90 mg ball was
prepared by rolling the IL polymer 2. The ball was then left for 20 s at
room temperature. The ball was then dropped onto a hard Bakelite
surface, in front of a 12 in. ruler. The highest point to which the ball
The supramolecular ionic materials were prepared by
dissolving 2 and either dodecandioic acid, stearic acid, oleic
acid, or 15-oxo-2,5,8,11,14-pentaoxaoctadecan-18-oic acid in a
volatile organic solvent (e.g., DCM) followed by removal of the
solvent and volatiles under high vacuum at 80 °C. The samples
were then cooled to room temperature. The resulting ionic
materials exhibit strikingly different physical and rheological
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dx.doi.org/10.1021/ma3002092 | Macromolecules 2012, 45, 2509−2513