Macromolecules
Article
spectrometer. TGA measurements were performed on a Thermal
Advantages (TA) Q500 at a heating rate of 10 °C min−1 under an
atmosphere of nitrogen. DSC measurements were performed on a
Thermal Advantages Q2000 with a heating or cooling rate of either 10
or 20 °C min−1 under an atmosphere of nitrogen. The samples were
subjected to two heating/cooling cycles prior to recording the data
that are presented herein. Mechanical properties were measured using
an Instron 5982. XRD analyses were performed using a Rigaku
SmartLab powder X-ray diffractometer. Polymer crystallinity was
calculated using the following equation: xC = [IC/(IC + IA)] × 100,
where xC = % crystallinity, IC = area of the crystalline region, and IA =
area of the amorphous region.43 Polymer films were prepared using a
Caver Hydraulic Laboratory Press (MH-C 4389). Melting points
were determined with an MPA 100 Optimelt automated melting
point system and are uncorrected.
Synthesis of 3. Furan-2,5-dione (2) (197.0 g, 2.0 mol),
acetophenone (9.4 mL, 80.6 mmol), and acetonitrile (2.6 L) were
added to a jacketed flask (2.6 L) at 37 °C under a positive flow of
nitrogen. A tube connected to a cylinder of ethylene was then
immersed into the solution and ethylene gas was slowly introduced.
Upon the introduction of ethylene, the nitrogen flow was ceased, and
the reaction mixture was kept under positive pressure through the
continuous release of excess ethylene gas. Photoirradiation of the
solution began after bubbling ethylene through the solution for 30
min, and the reaction progress was monitored by 1H NMR
spectroscopy. When conversions greater than 80% were reached (7
days at 37 °C), the residual solvent and the unreacted starting
materials were removed by reducing the pressure inside the reaction
vessel (100 °C, 4 mbar) for 24 h. The crude product 3 was directly
used without additional purification. Spectroscopic data were in
accord with the literature values.32 1H NMR (400 MHz, CDCl3): δ
3.45−3.60 (m, 2H), 2.68−2.86 (m, 2H), and 2.47−2.33 (m, 2H).
Synthesis of 4. Lithium aluminum hydride (10.6 g, 279.3 mmol)
was slowly added to anhydrous THF (350 mL) at 0 °C under a
positive flow of nitrogen. A solution of 3 (50 g, 396.5 mol) in THF
(60 mL) was slowly added dropwise to the resulting mixture over the
course of 1 h at 0 °C. The temperature of the resulting mixture was
then slowly increased to room temperature. After 12 h, the reaction
was quenched by adding 20 mL of aqueous NaOH (1 M) followed by
H2O (65 mL) at 0 °C over a period of 2 h under a positive flow of
nitrogen. Afterward, 50 g of sodium sulfate was added, and the
resulting mixture was stirred for 1 h to remove excess water. The
solution was then filtered and concentrated under reduced pressure.
Vacuum distillation (130 °C, 5 mbar) of the crude product afforded 4
as a colorless liquid (10.2 g, 22% yield over two steps). Spectroscopic
data were in accord with the literature values.32 1H NMR (400 MHz,
CDCl3): δ 3.76−3.92 (m, 2H), 3.54−3.65 (m, 2H), 2.63−2.80 (br,
2H), 1.94−2.08 (m, 2H), and 1.47−1.62 (m, 2H).
H2SO4 (3.0 mL, 56.0 mmol), i-PrOH (158 mL), and aqueous H2O2
(35 wt %.) (33.6 g, 345.7 mmol). Upon warming to room
temperature, the reaction mixture was stirred for 16 h. Following
cooling of the reaction mixture to 0 °C, 184 mL of an aqueous
solution saturated with NaHCO3 and 184 mL of an aqueous solution
of Na2SO3 (1.5 M) were added to the vessel to quench the reaction.
The resulting mixture was then extracted twice with a mixture of i-
PrOH/CHCl3 (3:7 v/v) and the combined organic phases were dried
over MgSO4. Evaporation of the residual solvent followed by column
chromatography using MeOH/EtOAc (1:9 v/v) as the eluent
afforded 6 as an epimeric mixture in 79% yield (14.2 g). Spectroscopic
data were in accord with the literature values.32 1H NMR (400 MHz,
CDCl3): δ 3.35−3.52 (br, 2H), 3.04−3.18 (m, 2H), 2.84−2.98 (m,
5H), 2.28−2.45 (m, 2H), and 1.56−1.73 (m, 2H).
Synthesis of 7. Compound 6 (33.8 g, 259.6 mmol) was dissolved
in CH2Cl2 (667 mL) at room temperature under a positive flow of
nitrogen. The reaction flask was cooled to −40 °C (dry ice/
acetonitrile). The cooled flask was charged with 42 mL of pyridine
followed by a solution of SO2Cl2 (21 mL, 259.8 mmol) and CH2Cl2
(200 mL), which was added dropwise. After 1 h, an aqueous solution
of HCl (1 N, 863 mL) was added to quench the reaction. The
solution was extracted twice with a mixture of i-PrOH/CHCl3 (3:7 v/
v) (500 mL), and the combined organic phases were dried over
MgSO4. Evaporation of the residual solvent under reduced pressure
followed by column chromatography using EtOAc/n-hexane (1:1 v/
v) as an eluent afforded 7 as an epimeric mixture in 91% yield (39.0
g). Spectroscopic data were in accord with the literature values.32 1H
NMR (400 MHz, CDCl3): δ 4.94−5.03 (d, 1H), 4.80−4.89 (d, 1H),
3.35−3.51 (m, 1H), 3.15−3.35 (m, 2H), 2.97−3.12 (m, 1H), 2.09−
2.45 (m, 3H), 1.70−1.86 (m, 1H), and 1.56−1.70 (m, 1H).
Synthesis of 1. Under a positive flow of nitrogen at room
temperature, t-BuOK (38.4 g, 342.2 mmol) was dissolved in dimethyl
sulfoxide (DMSO) (575 mL). A solution of compound 7 (18.8 g,
114.2 mmol) dissolved in DMSO (60 mL) was then slowly added to
the solution containing t-BuOK over the course of 3 h, and the
resulting mixture was stirred for additional 12 h at room temperature.
The reaction flask was subsequently connected to a glass distillation
apparatus and heated to 90 °C. Reduction of the pressure to 250 mbar
facilitated the removal of a gaseous product, which was presumed to
be sulfur monoxide (SO). After 1 h, the temperature of the receiving
flask was cooled to −78 °C (acetone/dry ice) and the pressure was
reduced to 10 mbar in increments of 50 mbar over the course of 4 h.
Once the pressure reached 50 mbar, the distillation was conducted for
an additional 1 h. The collected product was washed with a saturated
brine solution (15 mL × 3) and water (15 mL), which afforded 1 in
27% yield (7.4 g). Spectroscopic data were in accord with the
literature values.32 1H NMR (400 MHz, CDCl3): δ 6.30−6.36 (t,
2H), 3.22−3.32 (m, 2H), 2.10−2.27 (m, 2H), and 1.54−1.66 (m,
2H).
Synthesis of Poly(1). Bicyclo[2.2.0]hex-2-ene (1) (0.1 g, 1.2
mmol) and anhydrous THF (3.8 mL) were added to an air-free
reaction flask (10 mL) at −20 °C under a positive flow of nitrogen. A
solution of G3 dissolved in anhydrous THF (4.4 mg in 0.3 mL) was
injected and the resulting mixture was gently stirred for 1 h. The
reaction was quenched upon the addition of ethyl vinyl ether (0.1
mL), and the resulting mixture was concentrated under vacuum
without exposure to air. Poly(1) was directly characterized and used
for the synthesis of H-poly(1) without further purification as
precipitation resulted in the formation of a cross-linked polymer.36
1H NMR (400 MHz, CDCl3): δ 5.36−5.63 (br, 2H), 2.92−3.28 (br,
2H), 1.95−2.25 (br, 2H), and 1.60−1.95 (br, 2H).
Synthesis of 5. Compound 4 (16.2 g, 139.5 mmol) was dissolved
in anhydrous CH2Cl2 (700 mL) at −15 °C under a positive follow of
nitrogen. A solution of MsCl (25.0 mL, 323.0 mmol) was then quickly
poured into the solution of 4 followed by dropwise addition of Et3N
(40.8 mL). The temperature of the reaction mixture was then slowly
increased to room temperature. After 1 h, the reaction was quenched
by addition of an aqueous solution of HCl (1 M, 380 mL). Following
extraction using a mixture of i-PrOH and CHCl3 (3:7 v/v), the
resulting organic layer was dried over magnesium sulfate and
concentrated under reduced pressure. Purification of the resulting
pale brown liquid using column chromatography and hexane/ethyl
acetate (3:1 v/v) as the eluent afforded the pure product as a pale
white solid (36.1 g, 95% yield). Spectroscopic data were in accord
with the literature values.32 1H NMR (400 MHz, CDCl3): δ 4.34−
4.42 (m, 2H), 4.26−4.33 (m, 2H), 3.01−3.07 (s, 6H), 2.87−2.95 (br,
2H), 2.11−2.22 (m, 2H), and 1.79−1.89 (m, 2H). mp 38 °C (lit. 36−
38 °C).
Synthesis of H-Poly(1). Under a positive flow of nitrogen, a
reaction vessel was charged with o-xylene (50 mL), a solution of
poly(1) (0.1 g) in o-xylene (10 mL), tosylhydrazide (11.6 g, 62.3
mmol), a few crystals of BHT (3 mg), and triethylamine (6.6 mL,
47.3 mmol). The resulting mixture was heated to 130 °C, and the
progress of the reaction was monitored by analyzing aliquots that
Synthesis of 6. Compound 5 (37.7 g, 138.4 mmol) was dissolved
in a mixture of EtOH/H2O (5:2 v/v) (276 mL) and sodium sulfide
nonahydrate (40.0 g, 166.5 mmol) at room temperature, and then
refluxed at 95 °C for 12 h. The corresponding reaction flask was then
cooled to 0 °C and charged with a concentrated aqueous solution of
1
were periodically removed from the reaction vessel using H NMR
spectroscopy. After 48 h, the resulting mixture was concentrated
under reduced pressure and poured into excess cold CH3OH (200
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Macromolecules XXXX, XXX, XXX−XXX