Supporting Information
© Wiley-VCH 2006
69451 Weinheim, Germany
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Ambient
Temperature
Living
Anionic
Polymerization
of
Phosphaalkenes: Homopolymers and Block Copolymers with
Controlled Chain Lengths
Kevin J. T. Noonan and Derek P. Gates*
Department of Chemistry
University of British Columbia
2036 Main Mall, Vancouver, British Columbia, CANADA V6T 1Z1
Experimental Section
General Procedures. All manipulations of air and/or water sensitive compounds were
performed under pre-purified nitrogen using standard high vacuum or Schlenk techniques or in an
Innovative Technology Inc. glovebox. 13C, and 31P NMR spectra were recorded at room temperature on a
Bruker Avance 300 MHz spectrometer. Chemical shifts are reported relative to: CDCl3 (δ=77.23 for 13C);
85% H3PO4 as an external standard (δ = 0.0 for 31P).
Absolute molecular weights were determined by triple detection gel permeation chromatography (GPC –
triple detection) using a Waters liquid chromatograph equipped with a Waters 515 HPLC pump, Waters
717 plus autosampler, Waters Styragel columns (4.6x300mm), HR2 x 2 and HR4, Waters 2410 differential
refractometer (refractive index detector, λ = 940 nm), Wyatt tristar miniDAWN (laser light scattering
detector, λ = 690 nm) and a Wyatt ViscoStar viscometer. A flow rate of 0.3 mL/min was used and samples
were dissolved in THF (ca. 2 mg/ml). The dn/dc of 3a and 3b were determined using a Waters 410
Differential Refractometer (λ = 940 nm).
Materials. Hexanes was dried by passing through activated alumina columns.1 1,2-dimethoxyethane
(glyme) was distilled from sodium/benzophenone and degassed immediately prior to use.2 MeOH was
degassed prior to use. CDCl3 was purchased from Aldrich and distilled from P2O5 and stored over 3Å
molecular sieves.2 Benzophenone was purchased from Aldrich and sublimed prior to use. KOH was
purified by recrystallization from hot ethanol.2 nBuLi (1.6 M in hexane) was purchased from Aldrich and
titrated prior to use to determine concentration.3 1a and 1b was prepared according to literature
procedures.4
Purification of 1: Crude 1 was distilled (bp = 150 -160 oC, 0.01 mmHg) and the distillate was
recrystallized from hexanes (x2). The compound was ground into a fine powder and dried in vacuo for 12
hours at 60 oC. 1H NMR was used to confirm purity.
General Procedure for the Living Anionic Polymerization of 1
Preparation of controlled molecular weight poly(methylenephosphine)s 3a and 3b. A representative
homopolymerization of 3a using M:I = 50:1 is described. The reaction was performed in the glovebox. To a
stirred solution of 1a (0.25 g, 0.79 mmol) in 1,2-dimethoxyethane (2 mL) was added nBuLi (11 µL, 16
µmol, 1.45 M). The reaction mixture immediately turned a deep red color. The conversion of 1a (234 ppm)
to 2a (-7 ppm) was monitored by 31P NMR spectroscopy. Upon complete conversion to 2a (ca. 12-15 h)
degassed MeOH (1 drop) was added to the deep red solution. An immediate loss of color was observed and
resultant yellow reaction mixture was added dropwise into hexanes (2 x 40 mL) under N2. The polymer
was isolated by filtration and dried in vacuo for 4 hours at 100 oC. Yield = 185 mg (74%)
GPC: Mn = 14 800 g mol-1; PDI = 1.08.
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Preparation of poly(methylenephosphine) 3a for Determination of kp: To a stirred solution of 1a (0.127
g, 0.79 mmol) in dry 1,2-dimethoxyethane (1 mL) was added nBuLi (5.4 µL, 7.8 µmol, 1.45 M) was added
in the glovebox. The reaction mixture was transferred to an NMR tube and 31P NMR spectra were recorded
every 12 minutes until the was complete (72 scans, 3 min) A relaxation delay 2 s for a 30o tip angle was
used to ensure accurate integrations (for 1a, t1 = 1.33 s). Each spectrum was integrated to determine the
ratios of monomer to polymer and ln ([M]o/[M]) was plotted versus time. Reproducible values of kp were
obtained in 3 separate experiments.
kp = 21 L mol-1 h-1.
Procedure to obtain molecular weight vs monomer conversion data: To a stirred solution of 1a (1.25 g,
3.95 mmol) in dry 1,2-dimethoxyethane (10 mL) was added nBuLi (55 µL, 80 µmol, 1.45 M) was added in
the glovebox. Aliquots were removed from the reaction mixture approximately every 30 min between 4 –
7.5 h. Each aliquot was analyzed by 31P NMR spectroscopy (128 scans, relaxation delay 2 s for a 30 o tip
angle) to determine the ratio of monomer to polymer. Subsequently, each sample was immediately
quenched with MeOH (1 drop) and precipitated using hexanes (4 x 40-50 mL). The samples were dried for
several hours in vacuo at 100 oC and absolute molecular weights were determined. Mn was plotted versus
conversion. The reproducibility of these results were confirmed by repeating this experiment several times.
Preparation of polystyrene–b-poly(methylenephosphine) 4: In the glovebox, styrene (0.3 g, 2.88 mmol)
was dissolved in 1 mL of toluene to which was added nBuLi (20 µL, 29 µmol, 1.45 M). The solution
turned orange immediately and was stirred for 1 h. A small aliquot was removed to determine polystyrene
chain length, then a solution of 1a in 2 mL glyme was rapidly added to the living polystyrene. The solution
immediately took on a deep red color. 31P NMR spectroscopy was used to confirm complete consumption
of 1a. Upon completion, the polymer was quenched with MeOH (1 drop), precipitated with hexanes (2 x
40 mL) and dried overnight in vacou at 100 oC. Yield = 318 mg (60%).
Styrene homopolymer – GPC: Mn = 13 300 g mol-1; PDI = 1.07.
Polystyrene–b-poly(methylenephosphine) – GPC: Mn = 20 900 g mol-1; PDI = 1.03.
31
P and 13C NMR spectra are shown in Figures 8 and 9.
1.
A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, F. J. Timmers, Organometallics
1996, 15, 1518.
2.
W. L. F. Armarego, D. D. Perrin, Purification of Laboratory Chemicals. 4th Ed. ed.; Butterworth
Heinemann Press: Vol. 2, p.429 on purification of NaOH.
3.
A. F. Burchat, J. M. Chong, N. Nielsen, J. Organomet. Chem. 1997, 542, 281.
4.
V. G. Becker, W. Uhl, H.-J.Wessely, Z. Anorg. Allg. Chem. 1981, 479, 41.
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Figure 1. Graph of refractive index response vs. concentration of 3a in glyme (measured on Waters 410
Differential Refractometer calibrated with NaCl solutions). The slope of the best fit line is used to calculate
dn/dc.
Figure 2. Graph of refractive index response vs. concentration of 3b in glyme (measured on Waters 410
Differential Refractometer calibrated with NaCl solutions). The slope of the best fit line is used to calculate
dn/dc.
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Figure 3. GPC trace of 3a (Table 1, entry 3) Mn = 14800. (red trace – viscometer signal, green trace –
refractive index signal, black trace – laser light scattering signal).
Figure 4. GPC trace of 3b (Table 1, entry 6) Mn = 13600. (red trace – viscometer signal, green trace –
refractive index signal, black trace – laser light scattering signal).
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Figure 5. Refractive index traces of 3a with increasing Mn (black trace – M:I = 100:1, blue trace – M:I =
50:1, pink trace – M:I = 33:1, green trace – M:I = 25:1.
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Figure 6. GPC trace of styrene homopolymer prior to diblock copolymerization with 1a. M:I = 100:1. Mn
= 13300 (red trace – viscometer signal, green trace – refractive index signal, black trace – laser light
scattering signal).
Figure 7. GPC trace of block copolymer 4. Mn = 20 900 (red trace – viscometer signal, green trace –
refractive index signal, black trace – laser light scattering signal).
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Figure 8. 31P NMR of block copolymer 4 with Mn = 20 900 g mol-1. We speculate that the small shoulder is
due to the polystyrene-block-poly(methylenephosphine) switching group.
Figure 9. 13C NMR of block copolymer 4 with Mn = 20 900 g mol-1. (*) indicates CDCl3.