Macromolecules
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CH2 CH2 CO protons at 2.66 ppm) and 4H (O
COCH2CH2CH2CH2Si protons at 4.09 ppm) versus 818 for
dimethylsiloxane (SiCH3 at 0.07 ppm)), which corresponds to an
average molecular weight of ∼10 600 g·mol−1 (yield: 81%). The same
procedure using a larger amount of octamethylcyclotetrasiloxane (D4,
18.08 g, 61 mmol) and 2a (0.60 g, 1.1 mmol) yielded 14.14 g of a
polysiloxane chain 3b constituted of 313 dimethylsiloxane units, which
correspond to an average molecular weight of 23 700 g·mol−1 (yield:
77%).
SiCH2CH2CH2O); 2.87 (s, 1H, CCH); 4.14 (t, 2H, J = 7.0 Hz,
SiCH2CH2CH2O). 13C NMR (CDCl3; 150 MHz, δ): −0.2 (SiCH3);
2.0 (Si(CH3)3); 13.5 (SiCH2CH2CH2O); 22.4 (SiCH2CH2CH2O);
68.8 (SiCH2CH2CH2O); 74.5 (CCH); 75.0 (CCH); 153.0 (C
O). HRMS (EI): m/z [M+] calculated = 332.1295, found = 332.1279.
Synthesis of Propiolate-Terminated PEOs 9a (750 MW) and 9b
(2000 MW). Propiolate-terminated monomethoxy poly(ethylene
oxide) 9a: in a round-bottomed flask containing monomethoxypoly-
(ethylene-oxide) (av. mol. wt: 750) (15.0 g, 20.0 mmol), was
successively added propiolic acid (4.2 g, 60.0 mmol), toluene (90 mL)
and a catalytic amount of p-toluenesulfonic acid (0.5 g, 2.6 mmol).
The flask was equipped with a Dean−Stark apparatus, and heated to
reflux with azeotropic removal of water. Completion of the reaction
was monitored by 1H NMR, by comparison of the 3 protons of
terminal methoxy with the appearance of the methylenic ester protons
at 4.34 ppm (ca. 20 h). The solution was then cooled to room
temperature, and washed three times with 50 mL of an aqueous
potassium carbonate solution. The organic phase was then dried over
magnesium sulfate and concentrated in vacuo, and the crude product
was directly loaded onto a chromatography column packed with silica
gel. Elution started with pure dichloromethane, then increasing
amounts of methanol were added to the eluent (up to 5%, v:v). The
fractions containing the propiolate ester were combined, evaporated
under reduced pressure to afford pure monopropiolate-terminated
monomethoxy poly(ethylene oxide), (12.1 g, 77% yield).
1H NMR (CDCl3, 200 MHz, δ): 0.01 (s, 818H for 3a and 1875H
for 3b, SiCH3); 0.49 (t, 4H, J = 8.2 Hz, SiCH2CH2CH2CH2); 1.37 (m,
4H, SiCH2CH2CH2CH2); 1.62 (m, 4H, SiCH2CH2CH2CH2); 2.46 (s,
2H, CCH); 2.63 (s, 8H, OCCH2CH2CO); 4.06 (t, 4H, J = 6.0
Hz, SiCH2CH2CH2CH2); 4.67 (s, 4H, CH2CCH).
Synthesis of Propiolate-Terminated Polysiloxane 4a. 1,3-Bis-
(propiolatobutyl)tetramethyldisiloxane (2b) was synthesized following
19
the procedure by Gonzaga et al.
The same equilibration
methodology as outlined in the above procedure (synthesis of 3a
and 4a) was followed, but using 2b (0.78 g, 2.0 mmol) as the end
group, with D4 (34.09 g, 115.0 mmol) and triflic acid (200 μL, 2.3
mmol), yielding 29.77 g of propiolate-terminated polysiloxane, 4a. The
polysiloxane chain was constituted of 220 dimethylsiloxane units,
corresponding to an average molecular weight of 16,500 g·mol−1
1
(yield: 85%) determined by H NMR and confirmed by GPC (Mn=
17 000 g·mol−1; PDI = 1.6). 1H NMR (CDCl3, 200 MHz, δ): 0.07 (s,
1320H, SiCH3); 0.56 (t, 4H, J = 8.3 Hz, SiCH2CH2CH2CH2); 1.37
(m, 4H, SiCH2CH2CH2CH2); 1.68 (m, 4H, SiCH2CH2CH2CH2);
2.86 (s, 2H, CCH); 4.20 (t, 4H, J = 6.5 Hz, SiCH2CH2CH2CH2).
Synthesis of Poly(alkyne)-Functionalized Polymer 5. In a 100 mL
round-bottomed flask, (aminopropyl)methylsiloxane-dimethylsiloxane
copolymer (6−7 mol % (aminopropyl)methylsiloxane, 11.30 g, 10.1
mmol) and 1a (1.89 g, 12.1 mmol) were dissolved in dry DCM (50
mL). The mixture was cooled at −20 °C in a dry ice/acetone bath, and
a catalytic amount of DMAP (0.02 g, 0.2 mmol) was added. EDC·HCl
(2.33 g, 12.1 mmol) and additional DCM (15 mL) were slowly added.
The reaction was covered, purged with nitrogen and allowed to stir
under a positive pressure of nitrogen for 48 h. The mixture was then
washed with 2 × 50 mL of 0.1 M HCl (it took several hours for the
mixture to phase separate) followed by 2 × 25 mL of distilled water.
The organic phase was dried over MgSO4, gravity filtered and the
volatiles removed in vacuo to yield 10.60 g (84% yield) of the title
compound as a faint yellow oil.
1H NMR (CDCl3, 600 MHz, δ): 4.34 (t, 2H, −COOCH2−, J = 6.0
Hz), 3.74 to 3.55 (m, ∼ 60H, −OCHH2CH2O−), 3.37 (s, 3H,
OCH3), 2.89 (s, broad, 1H, HCCCOO). 13C NMR (CDCl3, 125
MHz, δ): 152.68, 75.67, 74.56, 71.94, 70.57, 68.57, 65.24, 59.03.
+
HRMS (ES positive mode): m/z [M + NH4 ] calculated = 806.4749,
found = 806.4768.
Monopropiolate-terminated monomethoxy poly(ethylene oxide)
9b: in a round-bottomed flask containing monomethoxy poly(ethylene
oxide) (av. mol. wt: 2000) (20.0 g, 10 mmol), was successively added
propiolic acid (2.8 g, 40 mmol), toluene (70 mL), and a catalytic
amount of p-toluenesulfonic acid (0.75 g, 3.9 mmol). The flask was
equipped with a Dean−Stark apparatus, and heated with azeotropic
1
removal of water. Completion of the reaction was monitored by H
NMR, by comparison of the three protons of terminal methoxy with to
the appearance of the methylenic ester protons at 4.27 ppm. Once the
reaction was complete, the mixture was then concentrated in vacuo,
and the crude product was dissolved in a minimal amount of
dichloromethane. The mixture was then added dropwise to a beaker
containing ice-cold diethyl ether (150 mL). Once complete, the
mixture was allowed to stir for a further 20 min to ensure complete
precipitation. The precipitate was then collected using a fritted funnel
and dried under reduced pressure. The white powder was redissolved
in DCM, and the precipitation procedure (drop by drop addition into
ice-cold diethyl ether) was repeated. The precipitate was collected in a
fritted funnel, dried under reduced pressure in a desiccator to afford
the title compound (16.8 g; 82%) as a white powder.
1H NMR (CDCl3, 600 MHz, δ): 0.07 (s, 84H, SiCH3); 0.50 (m,
2H, SiCH2CH2CH2N); 1.53 (m, 2H, SiCH2CH2CH2N); 2.47 (m, 3H,
OCCH2CH2CON and CCH); 2.72 (m, 2H, O
CCH2CH2CON); 3.22 (m, 2H, SiCH2CH2CH2N); 4.68 (s, 2H,
CH2CCH). 13C NMR (CDCl3; 150 MHz): δ = −0.33, 1.25, 1.99,
14.12, 23.40, 31.10, 42.57, 52.33, 75.14, 171.02, 172.40.
Synthesis of Propiolate Functional Trisiloxane 7. In a round-
bottomed flask were successively introduced allyl alcohol (4.36 g, 75.0
mmol), bis(trimethylsiloxy)methylsilane (5.56 g, 25.0 mmol), and dry
toluene (25 mL). Karstedt’s platinum hydrosilylation catalyst
(platinum divinyltetramethyldisiloxane complex, solution in xylenes:
0.05 mL) was added, and the mixture was stirred at 50 °C in a dry
atmosphere (connected to a Drierite tube) for 16 h. The volatiles were
then removed in vacuo, and the light brown oily residue was directly
esterified as follow: propiolic acid (3.50 g, 50.0 mmol) in dry
dichloromethane (40 mL) was added, and the solution was cooled at
−20 °C using a dry ice/acetone bath. A catalytic amount of DMAP
(0.10 g, 0.8 mmol) was added, followed by small portions addition of
DCC (6.19 g. 30.0 mmol). Cooling at −20 °C was maintained for 8 h.
The mixture was then allowed to return to room temperature
(overnight). The DCM was evaporated in vacuo, and the residue
redissolved in dry diethyl ether. The insoluble dicyclohexyl urea was
removed by filtration. The filtrate was concentrated in vacuo and the
resulting oil was chromatographed over silica gel eluting using 1%
ethyl acetate in hexanes to afford 6.54 g (79% for the 2 steps) of the
title compound as a colorless oil.
1H NMR (CDCl3, 500 MHz, δ): 4.27 (t, 2H, −COOCH2−, J = 5.0
Hz), 3.47 to 3.68 (m, ∼ 233H, −OCHH2CH2O−), 3.31 (s, 3H,
−OCHH3), 3.01 ppm (s, 1H, HCCCOO). 13C NMR (CDCl3, 125
MHz, δ): 152.59, 75.62, 74.48, 71.88, 70.60, 68.50, 65.14, 58.97 ppm.
HRMS (ES positive mode): m/z [M + H]+ calculated = 2065.2008,
found = 2065.1916.
Azide Synthesis. Synthesis of Poly(azidopropylmethyl)-co-
(dimethylsiloxane) 6. The preparation of 6 is an improvement of
the previously published method by Gonzaga et al.19
(Chloropropylmethyl)siloxane-dimethylsiloxane copolymer
1
(14−16 mol % (chloropropyl)methylsiloxane, by H NMR
((Me2SiO)5.5(Cl(CH2)3MeSiO)1)n; 543.45 g/mol repeat unit)
20.00 g, 36.8 mmol of chloropropyl groups), NaN3 (3.62 g,
55.7 mmol) and (n-butyl)4NN3, (0.50 g, 1.8 mmol) were
dissolved in dry THF (60 mL). The mixture was refluxed with
stirring for 24 h. At this stage, the reaction was found to be
1
almost complete by H NMR spectroscopy. Additional (n-
butyl)4NN3 (0.30 g, 1.00 mmol) was therefore added, and the
mixture was refluxed an additional 24 h. THF was removed in
1H NMR (CDCl3; 200 MHz, δ): 0.02 (s, 3H, SiCH3); 0.08 (s, 18H,
Si(CH3)3); 0.47 (m, 2H, SiCH2CH2CH2O); 1.69 (m, 2H,
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dx.doi.org/10.1021/ma202785x | Macromolecules 2012, 45, 2276−2285