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Preparation of Chitin/Cellulose Composite Gels and Films with Ionic Liquids
Akihiko Takegawa, Masa-aki Murakami, Yoshiro Kaneko, Jun-ichi Kadokawa
PII: S0144-8617(09)00392- DOI: 10.1016/j.carbpol.2009.07. Reference: CARP 4303
To appear in: Carbohydrate Polymers
Received Date: 26 May 2009 Revised Date: 8 July 2009 Accepted Date: 16 July 2009
Please cite this article as: Takegawa, A., Murakami, M-a., Kaneko, Y., Kadokawa, J-i., Preparation of Chitin/ Cellulose Composite Gels and Films with Ionic Liquids, Carbohydrate Polymers (2009), doi: 10.1016/j.carbpol. 2009.07.
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1 Preparation of Chitin/Cellulose Composite Gels and
2 Films with Ionic Liquids
3 Akihiko Takegawa, Masa-aki Murakami, Yoshiro Kaneko, and Jun-ichi Kadokawa* 4 Department of Chemistry, Biotechnology, and Chemical Engineering, Graduate School of Science and 5 Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan 6 7 ABSTRACT 8 In this study, we performed preparation and characterizations of the chitin/cellulose composite gels and 9 films using the two ionic liquids, 1-allyl-3-methylimidazolium bromide and 1-butyl-3- 10 methylimidazolium chloride. First, chitin and cellulose were dissolved in each appropriate ionic liquid. 11 Then, the two liquids were mixed in the desired ratios at 100 oC to give the homogeneous mixtures. The 12 gels were obtained by standing the mixtures for 4 days. On the other hand, the films were obtained by 13 casting the mixtures on glass plates, followed by soaking in water and drying. The obtained gels and 14 films were characterized by XRD and TGA measurements. The mechanical properties of the gels and 15 films were evaluated under compressive and tensile modes, respectively. 16 17 Keywords: Chitin; Cellulose; Ionic liquid; Gel; Film 18 19 * Corresponding author. Tel.: +81 99 285 7743; fax: +81 99 285 3253.
20 E-mail address: [email protected]
47 films, and membranes have been prepared using these solvent systems (Zhang, Guo, & Du, 2002; Zheng, 48 Zhou, Du, & Zhang, 2002; Kondo, Kasai, & Brown Jr., 2004; Zhou, Zhang, & Guo, 2005; Liang, Zhang, 49 & Xu, 2007). 50 It has been reported that a variety of room temperature ionic liquids can be used to dissolve cellulose 51 (Liebert & Heinze, 2008; Feng & Chen, 2008). For example, it was found that 1-butyl-3- 52 methylimidazolium chloride (BMIMCl, Fig. 1) dissolved cellulose in relatively high concentrations 53 (Swatloski, Spear, Holbrey, & Rogers, 2002). In the following papers by the same research group, the 54 cellulose films were further obtained by casting the solutions of cellulose in BMIMCl onto a glass plate, 55 followed by reconstitution by the addition of water (Turner, Spear, Holbrey, & Rogers, 2004; Turner, 56 Spear, Holbrey, Daly, & Rogers, 2005). We have also studied preparation of new materials using 57 cellulose and ionic liquids (Murakami, Kaneko, & Kadokawa, 2007; Kadokawa, Murakami, & Keneko, 58 2008a). As the recent result in the course of the work, we reported formation of a gel from a solution of 59 cellulose in BMIMCl (Kadokawa, Murakami, & Kaneko, 2008b; Kadokawa, Murakami, Takegawa, & 60 Kaneko, 2009), which was obtained by keeping the solution at room temperature for several days. This 61 method for the preparation of the gel materials with ionic liquids has been extended to other 62 polysaccharides such as carrageenan and guar gum (Prasad, Kaneko, & Kadokwa, 2009; Prasad, Izawa, 63 Kaneko, Kadokawa, 2009). On the other hand, only a few examples have been reported regarding the 64 dissolution of chitin with ionic liquids (Xie, Zhang, & Li, 2006; Mantz, Fox, Green III, Fylstra, DeLong, 65 & Trulove, 2007; Wu, Sasaki, Irie, & Sakurai, 2008). For the development of studies on chitin using the 66 ionic liquids, therefore, we have considered to find other ionic liquids which can dissolve chitin. Then, 67 the dissolution of chitin with the ionic liquids can be extended to the further work, e.g., the production 68 of new materials composed of chitin. 69 On the basis of the above viewpoints, recently, we found that an ionic liquid, 1-allyl-3- 70 methylimidazolium bromide (AMIMBr, Fig. 1)) formed a clear liquid with chitin and evaluated its weak 71 gel nature by rheological analysis in a further work (Prasad et al., 2009). In the recent communication, 72 we also reported preparation and electrochemical properties of chitin/cellulose composite gel electrolyte
73 containing binary ionic liquids with aqueous H 2 SO 4 for an electric double layer capacitor (Yamazaki et 74 al., 2009). The composite gel was prepared from a homogeneous mixture obtained from a liquid of 75 chitin with AMIMBr and a liquid of cellulose with BMIMCl according to the similar method as that for 76 the aforementioned gel of cellulose with BMIMCl (Kadokawa, Murakami, & Kaneko, 2008b). 77 In this paper, we report the detailed study on the chitin/cellulose composite gels with the ionic liquids, 78 AMIMBr and BMIMCl, including characterization and mechanical property. Moreover, we also 79 describe preparation, characterization, and mechanical property of the chitin/cellulose composite films 80 with the ionic liquids. The films were simply obtained by soaking the homogeneous mixtures of 81 chitin/cellulose with AMIMBr/BMIMCl into water. 82 83 2. Experimental Section 84 2.1. Materials 85 Microcrystalline cellulose from Merck was used. Chitin powder from crab shells was purchased from 86 Nakalai Tesque, Inc. The degree of acetylation of the chitin sample was estimated by elemental analysis 87 data to be 94.6 %, which was in good agreement with that of a standard chitin (Kurita, 2001)). An ionic 88 liquid, BMIMCl, was purchased from Sigma – Aldrich Co. An ionic liquid, AMIMBr was prepared by 89 reaction of 1-methylimidazole with 3-bromo-1-propene according to the method modified from the 90 literature procedure (Zhao et al., 2005). 91 92 2.2. Preparation of chitin/cellulose composite gel with ionic liquids 93 A typical experimental procedure for preparation of chitin/cellulose composite gel with ionic liquids 94 was as follows (chitin : cellulose = 1 : 3, mol/mol). Mixtures of chitin (0.0420 g, 0.206 mmol) with 95 AMIMBr (0.860 g, 4.24 mmol) and of cellulose (0.100 g, 0.617 mmol) with BMIMCl (1.00 g, 5. 96 mmol) were independently heated at 100 oC for 24 h with stirring to give clear liquids of chitin (5 % 97 w/w) and cellulose (10 % w/w) in each ionic liquid, respectively. The two liquids were mixed and 98 heated at 100 o^ C for 1 h with stirring to form a homogeneous mixture. The resulting mixture was
124 Senstar LSC-1/30, Tokyo Testing Machine Co.). NMR spectra were recorded on a JEOL ECX 400 125 spectrometer. 126 127 3. Results and discussion 128 The chitin/cellulose composite gels with ionic liquids were prepared according to the similar 129 experimental manner as that for preparation of the gel of cellulose with BMIMCl (Fig. 2), described in 130 our previous publication (Kadokawa, Murakami, & Kaneko, 2008b). Since we had not found any ionic 131 liquids which had ability to dissolve both chitin and cellulose in sufficient concentrations for the present 132 study, two kinds of the ionic liquids, i.e., AMIMBr and BMIMCl were used as follows. The clear liquids 133 of chitin in AMIMBr (5 % w/w) and of cellulose in BMIMCl (10 % w/w) were independently prepared 134 by heating each mixture at 100 oC for 24 h. We already confirmed in the previous literature that 135 deacetylation, degradation, and decreasing the molecular weight of chitin did not frequently occur 136 during the experiment for the formation of the 5 % w/w clear liquid with AMIMBr (Prasad et al., 2009). 137 Then, the two liquids in desired ratios were mixed at 100 oC to form a homogeneous mixture. The 138 homogeneity of the mixture was confirmed by observation using a charge coupled device camera with 139 200 times magnification scale. After the mixture was transferred to an appropriate mold and kept 140 standing at room temperature for 4 days, the formed gel was taken out from the mold, soaked in acetone 141 for 10 min, and dried under ambient conditions to give a composite gel. When the feed molar ratios of 142 chitin to cellulose were 1 : 3 – 1 : 1, the gels were facilely formed. Increasing the molar ratio of chitin to 143 cellulose than 1 : 1 did not give the gel formation. 144 The molar ratios of each material in the gels were estimated as follows. First, the gel was subjected to 145 Soxhlet extraction with methanol to extract the ionic liquids. The molar amounts of chitin and cellulose 146 in the gel were calculated on the basis of a weight of the residual material and the feed ratio of the two 147 polysaccharides used for preparation of the gel. On the other hand, the methanol extract was 148 concentrated and analyzed by the 1 H NMR measurement. The molar amounts of the two ionic liquids 149 were calculated by the integrated ratios of the 1 H NMR spectrum using hydroquinone dimethyl ether as
150 an internal standard. On the basis of the above two calculations, the molar ratios of chitin, cellulose, 151 AMIMBr, and BMIMCl in the gel were estimated, which were shown in Table 1. By comparing the ratio 152 of each material in the gel of run 1 in Table 1 (chitin : cellulose : AMIMBr : BMIMCl = 1 : 1 : 19.5 : 153 9.7) with the corresponding feed ratio (chitin : cellulose : AMIMBr : BMIMCl = 1 : 1 : 20.0 : 9.3) for 154 the gel preparation, it was suggested that little ionic liquids were leached out during the gelation process. 155 The data in Table 1 also indicated that the larger amounts of AMIMBr were leached out during the 156 gelation process when the higher feed ratios of the chitin liquid with AMIMBr to the cellulose liquid 157 with BMIMCl were used for the gel preparation (run 2 and 3 in Table 1). 158 The XRD profiles of the gels in Fig. 3c-e exhibited little diffraction peaks due to the crystalline 159 structures of chitin and cellulose as observed in Fig. 3a-b. Figure 4 shows the TGA curves of the gels in 160 comparison with those of chitin and cellulose. The TGA curves of the gels in Fig. 4c-e exhibited weight 161 losses starting at around 200 oC, which were almost 100 oC lower than those of chitin and cellulose in 162 Fig. 4a-b. These characterizations indicated that the crystalline structures of the polysaccharides were 163 not maintained in the gels due to good miscibility of the two polysaccharides with the ionic liquids. The 164 TGA curves of the gels also showed weight losses of 12.9 – 14.5 % at temperatures up to 100 oC, which 165 were reasonably explained by evaporation of water. These data suggested that the gels contained 166 relatively large amounts of water, and accordingly the following similar gelation mechanism was 167 considered as that for the gel of cellulose with BMIMCl reported in our previous paper (Kadokawa, 168 Murakami, & Kaneko, 2008b). The present gels were gradually formed with absorption of water and 169 simultaneously exclusion of the excess ionic liquids. Thus, the aggregates of the polysaccharide chains 170 were formed during this process, which probably acted as cross-linking points for the gel formation. 171 The stress-strain curves of the gels under compressive mode were measured, which are shown in Fig. 172 5. The fracture stresses and strains were 44.6 – 130.0 kPa and 13.0 – 14.1 %, respectively. The 173 mechanical properties became more brittle with increasing the ratio of chitin in the gels. 174 The chitin/cellulose films were further obtained by casting the homogeneous mixtures of 175 chitin/cellulose with AMIMBr/BMIMCl onto a glass plate, followed by reconstitution in water. First, the
202 the higher contents of chitin. The presence of the slight amounts of the ionic liquids probably 203 contributed to the miscibility of the two polysaccharides in the films. 204 The stress-strain curves of the films in Fig. 8 indicated that the mechanical properties became more 205 elastic with decreasing the ratios of chitin to cellulose in the films. The fracture stresses and strains were 206 7.5 – 9.0 MPa and 3.7 – 11.0 %, respectively. 207 208 4. Conclusions 209 210 In this paper, we reported the preparation and characterizations of the chitin/cellulose composite gels 211 and films using the two ionic liquids, AMIMBr and BMIMCl. First, chitin and cellulose were dissolved 212 in each appropriate ionic liquid. Then, the two liquids were mixed in the desired ratios at 100 oC to give
213 the homogeneous mixtures. The gels were obtained by standing the mixtures for 4 days. On the 214 other hand, the films were obtained by casting the mixtures on glass plates, followed by soaking in water 215 and drying. The obtained gels and films were characterized by XRD and TGA measurements, which 216 showed relatively good miscibility among the polysaccharides and the ionic liquids in the materials. The 217 mechanical properties of the gels and films were changed depending on the ratios of chitin to cellulose 218 in the materials. 219 220 Acknowledgments 221 The authors acknowledge the financial support from KRI Inc., Kyoto, Japan. 222 223 References 224 Cai, J. & Zhang, L. (2005). Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous 225 solutions. Macromolecular Bioscience , 5 , 539-548. 226 Feng, L. & Chen, Z.-L. (2008). Research progress on dissolution and functional modification of 227 cellulose in ionic liquids. Journal of Molecular Liquids , 142 , 1-5.
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279 Wu, Y., Sasaki, T., Irie, S. & Sakurai, K. (2008). A novel biomass-ionic liquid platform for the 280 utilization of native chitin. Polymer , 49 , 2321-2327. 281 Xie, H., Zhang, S., & Li, S. (2006). Chitin and chitosan dissolved in ionic liquids as reversible sorbents 282 of CO 2. Green Chemistry, 8, 630-633. 283 Yamazaki, S., Takegawa, A., Kaneko, Y., Kadokawa, J., Yamagata, M., & Ishikawa, M. (2009). An 284 acidic cellulose-chitin hybrid gel as novel electrolyte for an electric double layer capacitor. 285 Electrochemistry Communications , 11 , 68-70. 286 Zhang, L., Guo, J., & Du, Y. (2002). Morphology and properties of cellulose/chitin blends membranes 287 from NaOH/thiourea aqueous solution. Journal of Applied Polymer Science, 86 , 2025-2032. 288 Zhao, D., Fei, Z., Geldbach, T. J., Scopelliti, R., Laurenczy, G., & Dyson, P. J. (2005). Allyl- 289 functionalised ionic liquids: synthesis, characterization, and reactivity. Helvetica Chimica 290 Acta , 88 , 665-675. 291 Zheng, H., Zhou, J., Du, Y., & Zhang, L. (2002). Cellulose/chitin films blended in NaOH/urea aqueous 292 solution. Journal of Applied Polymer Science, 86 , 1679-1683. 293 Zhou, D., Zhang, L., & Guo, S. (2005). Mechanisms of lead biosorption on cellulose/chitin beads. Water 294 Research, 39, 3755-3762. 295 296 297 298 299 300 301 302 303 304
305 Table 1.
306 Preparation and characterizations of chitin/cellulose composite gels with ionic liquids.
307 Run Molar ratio in feed Molar ratio in gel Fracture strain (kPa) Fracture strain (%)
308 (chitin : cellulose : AMIMBr : BMIMCl) (compressive mode)
309 1 1 : 1 : 20.0 : 9.26 1 : 1 : 19.5 : 9.7 44.6 14.
310 2 1 : 2 : 20.0 : 18.5 1 : 2 : 15.5 : 17.8 92.9 13.
311 3 1 : 3 : 20.2 : 27.3 1 : 3 : 16.3 : 27.4 130.0 14.
312
313 Table 2.
314 Preparation and characterizations of chitin/cellulose composite films with ionic liquids.
315 Run Molar ratio in feed Molar ratio in film Fracture strain (MPa) Fracture strain (%)
316 (chitin : cellulose : AMIMBr : BMIMCl) (tensile mode)
317 1 1 : 3 : 20.0 : 28.8 1 : 3 : 0.90 : 2.4 8.2 3.
318 2 1 : 5 : 20.0 : 48.4 1 : 5 : 0.58 : 2.0 7.5 5.
319 3 1 : 7 : 20.0 : 65.7 1 : 7 : 0.65 : 1.7 7.5 7.
320 4 1 : 9 : 19.7 : 76.5 1 : 9 : 0.43 : 1.7 9.0 11.
321
322
323
Br
N N Chitin
O
O HO NHAc
OH n Cl
N N Cellulose
O
O HO OH
OH n AMIMBr (^) BMIMCl Fig. 1
Fig. 2.
Fig. 3.
Fig. 4.
Strain(%)
Stress (kPa)
(a)
(b)
(c)
Fig. 5.
Stress (MPa)
Strain(%)
(a)
(b) (c)
(d)
Fig. 8.
