RSC Advances
Paper
1
7,26
of pore structures.
In this work, various solvents, including 6.08 (1H), 5.41 (1H), 4.25 (2H), 1.87 (2H), 1.25 (18H), 0.83 (3H).
1
3
MeOH (methanol), EtOH (ethanol), MeCN (acetonitrile), MeCN–
C-NMR (DMSO-d , d ppm): 135.74, 129.21, 123.68, 119.67,
6
EA (EA ¼ ethyl acetate) mixture, and EtOH–EA–H O mixture, are 109.04, 49.65, 31.78, 29.66, 29.51 (overlapped peaks), 29.48,
2
applied in polymerization to control the mesostructure and 29.39, 29.27, 29.19, 28.88, 25.86, 22.57, 14.32.
1
chemical composition of the imidazolium-type MPILs prepared
by copolymerizing DVB with ILs of 3-alkyl-1-vinylimidazolium NMR (DMSO-d
bromide (alkyl ¼ n-butyl, n-hexyl, n-octyl, n-dodecyl, or n-hexa- (1H), 6.05 (1H), 5.45 (1H), 4.24 (2H), 1.88 (2H), 1.26 (26H), 0.84
3-n-Hexadecyl-l-vinylimidazolium bromide (VI-C16): H-
6
, d ppm): 9.83 (1H), 8.37 (1H), 8.04 (1H), 7.38
1
3
6
decyl). Other synthetic conditions such as the initiator (3H). C-NMR (DMSO-d , d ppm): 135.78, 129.29, 123.68,
concentration and the molar ratio of the two monomers are also 119.71, 108.93, 49.57, 31.84, 29.66, 29.52 (overlapped peaks),
systematically investigated. CO2 sorption capability and 29.47, 29.38, 29.31, 29.20, 28.91, 25.96, 22.55, 14.31.
adsorption–desorption cycle are also tested to investigate their
27,28
potential application in adsorption.
2.2 Synthesis of mesoporous copolymers
The mesoporous poly(ionic liquid) was prepared through the
radical co-polymerization of 3-alkyl-1-vinylimidazolium
bromide (VI-C4, 6, 8, 12 and 16) and divinylbenzene (DVB), as
2. Experimental
1
2
.1 Synthesis of imidazolium-based ILs
sketched in Scheme 1. In a typical synthesis, DVB (11 mmol), VI-
C4 (10 mmol) and AIBN (azobisisbutyronitrile, 5.5 mmol) were
dissolved in the solvent (30 mL) in a three-necked ask under
3-Butyl-1-vinylimidazolium bromide (VI-C4) was synthesized
according to ref. 1 and the procedure was described in Scheme
. Typically, butyl bromide (50 mmol) and 1-vinylimidazole
ꢁ
nitrogen protection. The mixture was reuxed at 76 C for 24 h
1
with stirring. The solid was collected by ltration, washed with
(50 mmol) were mixed in a 100 mL ask with vigorous stirring
ꢁ
ꢁ
deionized water and ethanol and dried under vacuum at 50 C.
under nitrogen atmosphere. The mixture was reuxed at 70 C
for 24 h. Aer reaction, the top phase was poured out, and the
solid residue was washed three times with ethyl acetate and
ether, nally dried at 50 C for 12 h under vacuum. Similarly,
other imidazolium-based ionic liquids with different alkyl chain
Various other copolymers were synthesized by varying the
synthetic parameters including the solvent, initiator concen-
tration, initial chemical compositions and the ionic liquid
precursor such as using VI-C6, VI-C8, VI-C12 or VI-C16 to
instead of VI-C4.
ꢁ
length were synthesized using bromo-hexane, bromo-heptane,
1
-bromodecane and 1-bromohexadecane respectively. The cor-
2
.3 Characterization
responding structure analysis was summarized as follows.
1
3
-n-Butyl-l-vinylimidazolium bromide (VI-C4): H-NMR
Nitrogen sorption isotherms were measured at 77 K on a BEL-
SORP-MINI volumetric adsorption analyzer, and the sample was
outgassed in the degas port of the apparatus at 523 K for 3 h
prior to testing. The BET specic surface area was calculated
(DMSO-d , d ppm): 9.87 (1H), 8.34 (1H), 8.03 (1H), 7.37 (1H),
6
6
.09 (1H), 5.44 (1H), 4.24 (2H), 1.80 (2H), 1.23 (2H), 0.83 (3H).
C-NMR (DMSO-d , d ppm): 135.71, 129.32, 123.74, 119.70,
6
1
3
1
2
09.10, 49.54, 31.70, 29.73, 29.57 (overlapped peaks), 29.55,
0
using adsorption data acquired at a relative pressure (P/P )
9.44, 29.41, 29.17, 28.98, 25.95, 22.54, 14.37.
range of 0.05–0.22 and the total pore volume was determined
from the amount adsorbed at a relative pressure of about 0.99.
The pore size distribution (PSD) curves were calculated from the
adsorption branch of the isotherm using the Barrett–Joyner–
Halenda (BJH) algorithm. The CHN elemental analysis was
performed on an elemental analyzer Vario Elcube. FT-IR spectra
were recorded on a Nicolet iS10 FT-IR instrument (KBr discs) in
1
3-n-Hexyl-l-vinylimidazolium bromide (VI-C6): H-NMR
(DMSO-d , d ppm): 9.83 (1H), 8.35 (1H), 8.07 (1H), 7.38 (1H),
6
6
1
1
2
.05 (1H), 5.41 (1H), 4.23 (2H), 1.85 (2H), 1.24 (6H), 0.84 (3H).
3C-NMR (DMSO-d , d ppm): 135.67, 129.37, 123.75, 119.81,
6
09.11, 49.65, 31.68, 29.65, 29.61 (overlapped peaks), 29.54,
9.41, 29.41, 29.17, 28.92, 25.97, 22.52, 14.33.
1
ꢀ1
1
3-n-Octyl-l-vinylimidazolium bromide (VI-C8): H-NMR
the 4000–400 cm region. H NMR spectra were measured with
(
DMSO-d
6
, d ppm): 9.86 (1H), 8.32 (1H), 8.07 (1H), 7.38 (1H),
a Bruker DPX 300 spectrometer at ambient temperature in D6-
6
.08 (1H), 5.40 (1H), 4.25 (2H), 1.81 (2H), 1.20 (10H), 0.84 (3H).
DMSO using TMS as internal reference. CO
isotherms were measured at 298 K on a Micromeritics ASAP
020 volumetric adsorption analyzer. SEM image was per-
formed on a HITACHI S-4800 eld-emission scanning electron
microscope. UV-vis spectra were collected on the SHIMADZU
UV-2600 in the region of 220–850 nm.
2
adsorption
1
3
C-NMR (DMSO-d , d ppm): 135.72, 129.33, 123.75, 119.72,
6
1
2
09.07, 49.66, 31.67, 29.67, 29.51 (overlapped peaks), 29.68,
2
9.45, 29.21, 29.17, 28.91, 25.97, 22.53, 14.31.
1
3-n-Dodecyl-l-vinylimidazolium bromide (VI-C12): H-NMR
6
(DMSO-d , d ppm): 9.82 (1H), 8.31 (1H), 8.03 (1H), 7.39 (1H),
3
. Results and discussion
3.1 MPILs synthesized by VI-C6
The mesoporous polymers are synthesized by co-polymerization
of DVB and the vinylimidazolium-based ILs tethered with
different length of alkyl chains. The employed ILs can be dis-
solved in polar solvents, such as methanol, ethanol,
Scheme 1 Synthetic procedure of mesoporous poly(ionic liquid)s.
23390 | RSC Adv., 2014, 4, 23389–23395
This journal is © The Royal Society of Chemistry 2014