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tetrahydrofuran (THF) as an eluent at a flow rate of 1 mL
min21. Poly (methyl methacrylate) (PMMA) of narrow PDI was
used as calibration standard. Data analysis was done using
OmniSEC 4.2 software.
and filtrate was reduced to dryness to yield pale yellow Me6-
TREN.
Yield = 90%. 1H NMR (CDCl3, 400 MHz), d (in ppm) = 2.60 (t,
6H), 2.38 (t, 6H), 2.28 (s, 18H). (1H NMR spectrum of this Me6-
TREN has been shown in the supplementary section Fig. 4S,
2.2.4. Thermal analysis. Differential Scanning Calorimetry
(DSC) was carried out on a TA (DSC Q100 V8.1 Build 251)
instrument at a heating rate of 10 uC min21 under nitrogen
atmosphere. In this case the sample was heated to +150 uC
then cooled to 250 uC. The sample was again heated to +150
uC at the heating rate of 10 uC min21. The second heating cycle
curve was used to calculate the Tg of the polymers.
Thermogravimetric analysis (TGA) was carried out on a TA
(TGA Q50 V6.1 Build 181) instrument. In this case, a small
amount of sample (approx. 8 mg) was heated from room
temperature to 600 uC at the rate of 10 uC min21 under
nitrogen atmosphere.
ESI .)
3
2.5. Typical procedure for copolymerization of 1,1-bis
(ethoxycarbonyl)-2-vinylcyclopropane (BCVCP) and methyl
methacrylate (MMA) using CuBr/Me6-TREN
All the polymerization reactions were performed in a Schlenk
tube. In a typical polymerization reaction, the catalyst, CuBr
(0.0202 g, 1.41 6 1024 mol) was taken in a Schlenk tube and
was closed with a septum. Nitrogen was purged through it to
remove oxygen from the flask. Me6-TREN (0.055 g, 2.36 6 1024
mol) with a little amount of toluene was added to the flask
under constant nitrogen purging. Then BCVCP (0.4 g, 1.887 6
1023 mol) and MMA (0.7548 g, 7.55 6 1023 mol) were added to
the flask with continuous stirring and nitrogen purging. The
initiator, EBiB (0.018 g, 9.44 6 1025) was transferred to the
Schlenk tube and then the tube was immersed in the oil bath
already preheated at 105 uC and the polymerization reaction
was continued for 22 h. At different time intervals, the aliquot
was taken out and conversion was calculated gravimetrically.
The polymer solution was diluted with THF and was passed
through the alumina column to remove copper catalyst. Later
THF was evaporated and the resultant polymer was character-
ized.
2.3. Synthesis of 1,1-bis (ethoxycarbonyl)-2-vinylcyclopropane
(BCVCP)
1,1-Bis (ethoxycarbonyl)-2-vinylcyclopropane (BCVCP) was
synthesized as reported earlier.4,22
In this case, 60 mL dry THF and sodium hydride (1.132 g,
47.16 mmol) were taken in a 500 mL three neck R. B. flask, and
cooled to 0 uC. Diethyl malonate (3.772 g, 23.58 mmol) was
added to it dropwise under nitrogen atmosphere and stirring
was continued. After 1 h, a solution of trans-1,4-dibromo-2-
butene (5 g, 23.58 mmol.) in dry THF was added dropwise into
the R. B. flask with constant stirring for another 15 min at 0
uC. The reaction mixture was refluxed at 70 uC overnight. The
resulting mass was filtered off and washed with ethanol twice.
The combined filtrate was evaporated, and the residue was
distilled under reduced pressure. The product was character-
ized by 1H NMR, 13C NMR and DEPT data. Yield = 88%; 1H
NMR (CDCl3, 200 MHz), d (in ppm) = 1.25 (t, 6H), 1.48–1.7 (m,
2H), 2.49–2.61 (m, 1H), 4.25 (q, 4H), 5.0–5.52 (m, 3H). 13C NMR
(CDCl3, 100 MHz), d (in ppm) = 170.6–167.4 (.CLO), 133.1
(LCH), 118.4 (LCH2), 61.6–61.4 (–OCH2), 35.8 (.C(CO2Et)2),
31.1 (.CH–), 20.3 (–CH2–), 14.1, 14.0 (–CH3). DEPT-135 (100
MHz) d (in ppm) = 133.1, 118.5, 61.7–61.5, 31.1, 20.3, 14.2–
14.1. (NMR spectra are shown in the supplementary section in
1H NMR (400 MHz, CDCl3); d (in ppm) = 5.33 (LCH–), 4.15
(–OCH2), 3.59 (–OCH3), 2.53 (.CHLCH–CH2– protons from
BCVCP part), 1.5 to 2.0 (–CH2– proton from PMMA part), 0.84–
1.40 (different –CH3 protons of PBCVCP and PMMA unit).
2.6. Homopolymerization of BCVCP
Homopolymerization of BCVCP was carried out in a Schlenk
tube using the same procedure adopted for the copolymeriza-
tion of BCVCP and MMA. However, in this case, MMA, the
comonomer was not used. In a typical homopolymerisation,
BCVCP (0.7 g, 3.302 mmol), CuBr (0.0142 g, 9.906 6 1022
mmol), Me6-TREN (0.038 g, 0.165 mmol) and EBiB (0.0129 g,
6.604 6 1022 mmol) were taken in 0.5 mL toluene in a Schlenk
tube and the polymerization reaction was carried out for 22 h
at 105 uC.
Fig. 1S to 3S, ESI and also were compared with literature
3
report.20
)
1H NMR (200 MHz, CDCl3); d (in ppm) = 5.21 (LCH–), 4.17
(–OCH2), 2.51 (.CHLCH–CH2–), 1.24 (–CH3). (NMR spectrum
2.4. Synthesis of tris (dimethylaminoethyl) amine (Me6-TREN)
Me6-TREN was prepared according to the procedure described
earlier.24
has been shown in supplementary section Fig. 5S, ESI .)
3
2.7. General procedure for conventional radical ring opening
copolymerization of BCVCP and MMA in bulk
In a 500 mL R. B. flask, 46 mL acetic acid and 206 mL
acetonitrile were taken. Aqueous formaldehyde solution (6.78
g, 226.05 mmol) was added to the R. B. flask followed by
addition of tris(2-aminoethyl)amine (1 g, 6.08 mol) with
continuous stirring of the mixture for 1 h. It was then cooled
to 0 uC and sodium borohydride (3.37 g, 89.05 mmol) was
slowly added to the flask. The reaction mixture was stirred for
48 h at room temperature and then solvent was removed. The
residue was made strongly basic (pH . 11) with 3 M aq. NaOH.
It was then extracted with dichloromethane (DCM) three
times. DCM extract was dried with MgSO4 and then the solvent
was removed. The residue was dissolved in pentane, filtered
In a Schlenk tube BCVCP (0.3 g, 1.42 6 1023 mol), MMA (0.568
g, 5.68 6 1023 mol) and azobisisobutyronitrile (AIBN), (0.0058
g, 3.55 6 1025 mol) were taken at a time and the tube was
sealed with a silicone septum. Nitrogen was purged through it
to remove oxygen from the Schlenk tube. Then the tube was
immersed into the oil bath preheated at 105 uC. Within 10 min
the reaction mixture became highly viscous. The resultant
reaction mixture was dissolved in THF and the polymer was
precipitated using hexane as non solvent. The polymer was
characterized by GPC, DSC, TGA, IR and NMR.
14488 | RSC Adv., 2013, 3, 14486–14494
This journal is ß The Royal Society of Chemistry 2013