The synthesis routes of imidazolium ionic liquids are shown in
Scheme 1, and the details are described in Section 2.3. The reactionscould be readily carried out due to the strong nucleophilictiy and
steric accessibility of the number 3 position nitrogen atom in 1-
vinylimidazole and high reactivity of 1-bromobutane and methyl
iodide. Both [VBI]Br and [VMI]I are soluble in water, alcohols and
DMF, insoluble in ethyl ether, chloroform and tetrahydrofuran.
The copolymers for preparing OH form anion exchange
membranes based on two types of imidazolium ionic liquid
monomers were synthesized via free radical polymerization, as
mentioned in Section 2.3. The synthetic routes are shown in
Scheme 2 and Scheme 3. Because of the strong water affinity of
imidazolium ionic liquids, styrene was introduced to the polymer
backbone to adjust the hydrophilic-lipophilic balance of the
membranes. The properties of the copolymers could be tuned by
varying the monomer ratios in the reactants.
The feed ratio of IILs/styrene, nitrogen content of copolymers
and the molar ratio of IILs/styrene in copolymers are summarized
in Table 1. Sample A, B and C were polymerized by [VBI]Br with
styrene, while Sample D, E and F were polymerized by [VMI]I with
styrene. The Nitrogen only existed in the imidazolium cation
groups, hence, the amount of imidazolium groups in the copolymers
could be reflected by the nitrogen content and controlled
by varying the feed ratio of IILs/styrene. It can be seen in Table 1
that the nitrogen content of copolymers decreased with the
decreasing amount of ionic liquids. All the copolymers and OH
form anion exchange membranes obtained in this work are soluble
in alcohols and DMF, insoluble in ethyl ether, chloroform and
tetrahydrofuran. Thus, the membranes could be prepared by solution
casting method mentioned in Section 2.4.
Fig. 1 shows the results of FT-IR spectra analysis of IILs and
membranes. The strong peaks between 2800 and 3000 cm1 are
the characteristics of methyl and methane of the branch of imidazolium
cation. The sharp peak at 1572 cm1 is identified to the
stretching vibration of C]N and the peak at 1162 cm1 is identified
to the flexural vibration of CeH in the imidazole ring.
The synthesis routes of imidazolium ionic liquids are shown inScheme 1, and the details are described in Section 2.3. The reactionscould be readily carried out due to the strong nucleophilictiy andsteric accessibility of the number 3 position nitrogen atom in 1-vinylimidazole and high reactivity of 1-bromobutane and methyliodide. Both [VBI]Br and [VMI]I are soluble in water, alcohols andDMF, insoluble in ethyl ether, chloroform and tetrahydrofuran.The copolymers for preparing OH form anion exchangemembranes based on two types of imidazolium ionic liquidmonomers were synthesized via free radical polymerization, asmentioned in Section 2.3. The synthetic routes are shown inScheme 2 and Scheme 3. Because of the strong water affinity ofimidazolium ionic liquids, styrene was introduced to the polymerbackbone to adjust the hydrophilic-lipophilic balance of themembranes. The properties of the copolymers could be tuned byvarying the monomer ratios in the reactants.The feed ratio of IILs/styrene, nitrogen content of copolymersand the molar ratio of IILs/styrene in copolymers are summarizedin Table 1. Sample A, B and C were polymerized by [VBI]Br withstyrene, while Sample D, E and F were polymerized by [VMI]I withstyrene. The Nitrogen only existed in the imidazolium cationgroups, hence, the amount of imidazolium groups in the copolymerscould be reflected by the nitrogen content and controlledby varying the feed ratio of IILs/styrene. It can be seen in Table 1that the nitrogen content of copolymers decreased with thedecreasing amount of ionic liquids. All the copolymers and OHform anion exchange membranes obtained in this work are solublein alcohols and DMF, insoluble in ethyl ether, chloroform andtetrahydrofuran. Thus, the membranes could be prepared by solutioncasting method mentioned in Section 2.4.Fig. 1 shows the results of FT-IR spectra analysis of IILs andmembranes. The strong peaks between 2800 and 3000 cm1 arethe characteristics of methyl and methane of the branch of imidazoliumcation. The sharp peak at 1572 cm1 is identified to thestretching vibration of C]N and the peak at 1162 cm1 is identifiedto the flexural vibration of CeH in the imidazole ring.
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