International Journal of Biological Macromolecules 69 (2014) 35–38
Contents lists available at ScienceDirect
International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac
Short communication
Preparation of chitin nanofiber-reinforced carboxymethyl cellulose films Daisuke Hatanaka a , Kazuya Yamamoto a , Jun-ichi Kadokawa a,b,∗ a
Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan Research Center for Environmentally Friendly Materials Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran, Hokkaido 050-8585, Japan b
a r t i c l e
i n f o
Article history: Received 8 March 2014 Received in revised form 17 April 2014 Accepted 7 May 2014 Available online 20 May 2014 Keywords: Carboxymethyl cellulose Chitin nanofiber Electrostatic interaction Composite film Ionic polysaccharide
a b s t r a c t In this study, we investigated the preparation of chitin nanofiber (CNF)-reinforced carboxymethyl cellulose (CMC) films by their electrostatic interaction. First, CMC films and self-assembled CNF dispersions with methanol were prepared by casting technique and regeneration from chitin ion gels with an ionic liquid, respectively. Then, the CMC films were immersed in the dispersions with the different CNF contents, followed by centrifugation to obtain the desired composite films. The amounts of the absorbed CNFs on the films were calculated by the weight increases after the above compatibilization procedure. The presence of CNFs on the films was also confirmed by the SEM and IR measurements. The mechanical properties of the composite films were evaluated by tensile testing, which suggested the reinforcing effect of CNFs present on the CMC films. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Naturally occurring polysaccharides such as cellulose and chitin are the representative biomass resources on the earth [1,2] and have widely been studied for their potential to become environmentally benign substitutes for petroleum-based materials because of their eco-friendly and biodegradable properties [3,4]. Cellulose is the most abundant natural polysaccharide, which consists of a chain of -(1 → 4)-linked d-glucose residues and is a very important renewable resource used in a number of traditional applications, such as in furniture, clothing, and medical products [5,6]. Various derivatives of cellulose have also been synthesized and used in practical applications [7]. Carboxymethyl cellulose (CMC) is one of the most widely applied cellulose derivatives and shows good processabilities such as the film formation, which has practically been used in detergent, food, paper, and textile industries [8]. Because CMC has a number of carboxylic acid groups, it is an acidic polysaccharide (Fig. 1). The commercially available CMC is generally composed of its sodium salt form, which exhibits water solubility.
∗ Corresponding author at: Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan. Tel.: +81 99 285 7743; fax: +81 99 285 3253. E-mail address: [email protected] (J.-i. Kadokawa). http://dx.doi.org/10.1016/j.ijbiomac.2014.05.022 0141-8130/© 2014 Elsevier B.V. All rights reserved.
Chitin is a structurally similar polysaccharide as cellulose, but which has acetamido groups at C-2 position in place of hydroxy groups in cellulose [9–11]. Thus, it is an aminopolysaccharide composed of a chain of -(1 → 4)-linked N-acetyl-d-glucosamine residues (Fig. 1). Because the acetyl groups in the isolated chitin samples from natural sources are partially cleaved (generally several %), it can be considered as a basic polysaccharide having free amino groups. In this study, we have performed to prepare composite materials from the aforementioned acidic and basic polysaccharides by their electrostatic interaction. Specifically, we used self-assembled nanofibers as a chitin moiety for compatibilization with CMC. In the previous study, we found that such self-assembled chitin nanofibers with ca. 20–60 nm in width and several hundred nm in length were facilely obtained by regeneration from chitin ion gels with an ionic liquid, 1-allyl-3methylimidazolium bromide (AMIMBr, Fig. 1), using methanol, followed by sonication [12,13], which had been based on our investigation on the gelation of chitin with the ionic liquid [14]. In this paper, accordingly, we report the preparation of selfassembled chitin nanofiber (CNF)-reinforced CMC films by the electrostatic interaction on surface of the film according to the procedure in Fig. 2. The morphology and mechanical property of the resulting films were evaluated by the SEM measurement and tensile testing, respectively. The present approach facilely provides new bio-based composite materials from two abundant natural polysaccharides.
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D. Hatanaka et al. / International Journal of Biological Macromolecules 69 (2014) 35–38
Fig. 1. Chemical structures of carboxymethyl cellulose (CMC), chitin, and 1-allyl-3-methylimidazolium bromide (AMIMBr).
2. Experimental part
subsequently under ambient conditions and reduced pressure to give a CMC film.
2.1. Materials Carboxymethyl cellulose (sodium salt, Mw = 7 × 105 , degree of carboxymethylation = 90%) was purchased from Sigma–Aldrich Co. Chitin powder from crab shells was purchased from Wako Pure Chemical Industries, Ltd., Japan. The weight–average molecular weight and degree of deacetylation values of the chitin sample were estimated by viscometric and IR analyses to be 7 × 105 and 4%, respectively [15,16]. An ionic liquid, AMIMBr, was prepared by reaction of 1-methylimidazole with 3-bromo-1-propene according to the method modified from the literature procedure [17]. Other reagents and solvents were available commercially and used without further purification.
2.3. Preparation of self-assembled CNF dispersion A procedure was conducted according to our previous publication [12]. A mixture of chitin (0.12 g, 0.59 mmol) with AMIMBr (1.00 g, 4.92 mmol) was left standing at room temperature for 24 h, followed by heating at 100 ◦ C for 24 h with stirring to give a chitin ion gel with AMIMBr. The gel was then soaked in methanol (40 mL) at room temperature for 48 h, followed by sonication for 10 min to give a self-assembled CNF dispersion (CNF content; 3.0 mg/mL). The dispersion was diluted two and three folds with methanol to give dispersions with 1.5 and 0.75 mg/mL CNF contents, respectively. 2.4. Preparation of chitin nanofiber-reinforced CMC film
2.2. Preparation of CMC film A commercially available CMC sodium salt (0.50 g, 0.24 mmol) was dissolved with water (200 mL) and treated with cationexchange resin (Amberlite IR 120B NA) at room temperature for 5 h. After the resin was removed by filtration, the filtrate was concentrated and thinly casted on a paraffin film. Then, it was dried
A typical experimental procedure was as follows. The CMC film (20.2 mg, 2.1 cm × 1.2 cm) was immersed in 0.75 mg/mL CNF dispersion (5.0 mL, the amount of chitin; 0.019 mmol) and the system was subjected to centrifugation (2000 rpm) for 30 min twice. Then, the film was washed with methanol and dried under reduced pressure to give a CNF-reinforced CMC film.
Fig. 2. Schematic image for preparation procedure of self-assembled CNF-reinforced CMC film.
D. Hatanaka et al. / International Journal of Biological Macromolecules 69 (2014) 35–38
Fig. 3. IR spectra of (a) CMC sodium salt, (b) CMC film, (c) composite film from 3.00 mg/mL CNF dispersion, and (d) chitin powder.
2.5. Measurements Attenuated total reflection (ATR) IR spectra were recorded on a PerkinElmer Spectrum Two spectrometer. Scanning electron microscopy (SEM) images were obtained using an Hitachi SU-70 electron microscope. The stress–strain curves were measured using a tensile tester (Little Senster LSC-1/30, Tokyo Testing Machine). 3. Results and discussion Because CMC is commercially available as its sodium salt form, which shows water solubility, it has been converted into the free acid form for the preparation of the desired CNF/CMC composite film by their electrostatic interaction attributed to the presence of COOH and NH2 groups [18]. After an aqueous solution of the CMC
37
sodium salt was treated with cation-exchange resin, it was thinly casted and dried to give a CMC film having free carboxylic acid groups. The conversion of salt form to acid form was confirmed by the IR analysis. The IR spectrum of the CMC sodium salt showed carbonyl absorption at 1592 cm−1 due to the carboxylate salt (Fig. 3a). The absorption disappeared in the IR spectrum of the resulting film, whereas it newly exhibited carbonyl absorption at 1727 cm−1 due to the carboxylic acid (Fig. 3b). These IR spectra indicated the formation of the CMC film having the carboxylic acid groups. The resulting film showed water insolubility. Then, the self-assembled CNFs were absorbed on surface of the CMC film by the electrostatic interaction to produce the desired composite films. A commercially available chitin powder with degree of deacetylation = 4% was used and the self-assembled CNF dispersions were prepared by soaking chitin/AMIMBr ion gels in methanol, followed by sonication according to the previously reported procedure by us [12]. The aforementioned CMC films were immersed in the dispersions with different CNF contents (0.75, 1.5, and 3.0 mg/mL) (Fig. 2). The systems were subjected to centrifugation and the films were washed with methanol and dried to give the CNF/CMC composite films. The amounts of the absorbed CNFs per unit surface area on the CMC films were calculated by the weight increases of the resulting films from the CMC films used, which increased with increasing the CNF contents in the dispersions as follows; 13.9, 17.5, and 26.5 g/cm2 (CNF/CMC film) from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively. The surface morphologies of the composite films were investigated by the SEM measurement. The SEM images of all the films observed the presence of CNFs on surface of the films (Fig. 4). Furthermore, the images suggested the increases of the number of CNFs on the films with increasing the CNF contents in the dispersions, which were in good agreement with the trend of the CNF amounts determined by the weight calculation as aforementioned. The presence of chitin in the films was also confirmed by the IR measurement because the IR spectra of the resulting films exhibited carbonyl absorption at 1627 cm−1 due to the acetamido group in the chitin structure (Fig. 3d) in addition to that due to the carboxylic acid group, as representatively shown in Fig. 3c. However, the carbonyl absorption due to carboxylate, which took part into the electrostatic interaction with ammonium group, was not detected in the IR spectra. This is probably because of a little presence of the ammonium carboxylate only at the interfacial area between two materials. The mechanical properties of the composite films were evaluated by tensile testing. The stress–strain curves in Fig. 5 indicated obvious increases both in the fracture stress and strain values of the composite films compared with the CMC film. Specifically, the composite film obtained from 3.00 mg/mL CNF dispersion showed the much larger fracture stress and strain values (Fig. 5d) because its surface was largely covered by the CNFs as seen in Fig. 4c. These results strongly suggested the reinforcing effect of the CNFs present even on surface of the films. The previous study also reported the reinforcing effect by the presence of chitin whiskers on surface of a chitosan membrane [19].
Fig. 4. SEM images of (a)–(c) composite films from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively.
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D. Hatanaka et al. / International Journal of Biological Macromolecules 69 (2014) 35–38
facilely obtained by regeneration from the chitin ion gels, were a good candidate as the material component for the compatibilization with acidic polysaccharides. Therefore, this approach will be applied to other acidic polysaccharides to produce further practical bio-based materials in the future. References
Fig. 5. Stress–strain curves of (a) CMC film and (b)–(d) composite films from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively, under tensile mode; fracture stress and strain values are shown in the figure.
4. Conclusions In this paper, we reported the preparation of the CNF-reinforced CMC films by immersing the CMC films in the CNF dispersions, followed by drying. The amounts of the CNFs on the resulting films increased with increasing the CNF contents in the dispersions used. The SEM images of the films supported the nanofiber morphologies on the films. The reinforcing effect of CNFs present on the films was confirmed by tensile testing and the number of CNFs strongly affected enhancement of the mechanical property. The present study revealed that the self-assembled CNFs, which were
[1] J.M. Berg, J.L. Tymoczko, L. Stryer, Biochemistry, 6th ed., W.H. Freeman & Co., New York, 2006 (Chapter 11). [2] C. Schuerch, in: H.F. Mark, N. Bilkales, C.G. Overberger (Eds.), Encyclopedia of Polymer Science and Engineering, 13, 2nd ed., John Wiley & Sons, New York, 1986, pp. 87–162. [3] A. Rouilly, L. Rigal, J. Macromol, Sci. Polym. Rev C42 (2002) 441–479. [4] A.K. Mohanty, M. Misra, L.T. Drzal, J. Polym. Environ. 10 (2002) 19–26. [5] D. Klemm, B. Heublein, H.P. Fink, A. Bohn, Angew. Chem. Int. Ed. 44 (2005) 3358–3393. [6] D. Klemm, F. Kramer, S. Moritz, T. Lindström, M. Ankerfors, D. Gray, A. Dorris, Angew. Chem. Int. Ed. 50 (2011) 5438–5466. [7] E. Doelker, Adv. Polym. Sci. 107 (1993) 199–265. [8] A.M. Stephen, G.O. Philips, P.A. Williams, Food Polysaccharides and their Applications, Taylor & Francis, London, 1995. [9] K. Kurita, Mar. Biotechnol. 8 (2006) 203–226. [10] M. Rinaudo, Prog. Polym. Sci. 31 (2006) 603–632. [11] C.K.S. Pillai, W. Paul, C.P. Sharma, Prog. Polym. Sci. 34 (2009) 641–678. [12] J. Kadokawa, A. Takegawa, S. Mine, K. Prasad, Carbohydr. Polym. 84 (2011) 1408–1412. [13] R. Tajiri, T. Setoguchi, S. Wakizono, K. Yamamoto, J. Kadokawa, J. Biobased Mater. Bioenergy 7 (2013) 655–659. [14] K. Prasad, M. Murakami, Y. Kaneko, A. Takada, Y. Nakamura, J. Kadokawa, Int. J. Biol. Macromol. 45 (2009) 221–225. [15] M. Poirier, G. Charlet, Carbohydr. Polym. 50 (2002) 363–370. [16] Y. Shigemasa, H. Matsuura, H. Sashiwa, H. Saimoto, Int. J. Biol. Macromol. 18 (1996) 237–242. [17] D. Zhao, Z. Fei, T.J. Geldbach, R. Scopelliti, G. Laurenczy, P.J. Dyson, Helv. Chim. Acta 88 (2005) 665–675. [18] A.M. Bochek, L.D. Yusupova, N.M. Zabivalova, G.A. Petropavlovskii, Russ. J. Appl. Chem. 75 (2002) 645–648. [19] B. Ma, A. Qin, X. Li, X. Zhao, C. He, Mater. Lett. 120 (2014) 82–85.
Contents lists available at ScienceDirect
International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac
Short communication
Preparation of chitin nanofiber-reinforced carboxymethyl cellulose films Daisuke Hatanaka a , Kazuya Yamamoto a , Jun-ichi Kadokawa a,b,∗ a
Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan Research Center for Environmentally Friendly Materials Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran, Hokkaido 050-8585, Japan b
a r t i c l e
i n f o
Article history: Received 8 March 2014 Received in revised form 17 April 2014 Accepted 7 May 2014 Available online 20 May 2014 Keywords: Carboxymethyl cellulose Chitin nanofiber Electrostatic interaction Composite film Ionic polysaccharide
a b s t r a c t In this study, we investigated the preparation of chitin nanofiber (CNF)-reinforced carboxymethyl cellulose (CMC) films by their electrostatic interaction. First, CMC films and self-assembled CNF dispersions with methanol were prepared by casting technique and regeneration from chitin ion gels with an ionic liquid, respectively. Then, the CMC films were immersed in the dispersions with the different CNF contents, followed by centrifugation to obtain the desired composite films. The amounts of the absorbed CNFs on the films were calculated by the weight increases after the above compatibilization procedure. The presence of CNFs on the films was also confirmed by the SEM and IR measurements. The mechanical properties of the composite films were evaluated by tensile testing, which suggested the reinforcing effect of CNFs present on the CMC films. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Naturally occurring polysaccharides such as cellulose and chitin are the representative biomass resources on the earth [1,2] and have widely been studied for their potential to become environmentally benign substitutes for petroleum-based materials because of their eco-friendly and biodegradable properties [3,4]. Cellulose is the most abundant natural polysaccharide, which consists of a chain of -(1 → 4)-linked d-glucose residues and is a very important renewable resource used in a number of traditional applications, such as in furniture, clothing, and medical products [5,6]. Various derivatives of cellulose have also been synthesized and used in practical applications [7]. Carboxymethyl cellulose (CMC) is one of the most widely applied cellulose derivatives and shows good processabilities such as the film formation, which has practically been used in detergent, food, paper, and textile industries [8]. Because CMC has a number of carboxylic acid groups, it is an acidic polysaccharide (Fig. 1). The commercially available CMC is generally composed of its sodium salt form, which exhibits water solubility.
∗ Corresponding author at: Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan. Tel.: +81 99 285 7743; fax: +81 99 285 3253. E-mail address: [email protected] (J.-i. Kadokawa). http://dx.doi.org/10.1016/j.ijbiomac.2014.05.022 0141-8130/© 2014 Elsevier B.V. All rights reserved.
Chitin is a structurally similar polysaccharide as cellulose, but which has acetamido groups at C-2 position in place of hydroxy groups in cellulose [9–11]. Thus, it is an aminopolysaccharide composed of a chain of -(1 → 4)-linked N-acetyl-d-glucosamine residues (Fig. 1). Because the acetyl groups in the isolated chitin samples from natural sources are partially cleaved (generally several %), it can be considered as a basic polysaccharide having free amino groups. In this study, we have performed to prepare composite materials from the aforementioned acidic and basic polysaccharides by their electrostatic interaction. Specifically, we used self-assembled nanofibers as a chitin moiety for compatibilization with CMC. In the previous study, we found that such self-assembled chitin nanofibers with ca. 20–60 nm in width and several hundred nm in length were facilely obtained by regeneration from chitin ion gels with an ionic liquid, 1-allyl-3methylimidazolium bromide (AMIMBr, Fig. 1), using methanol, followed by sonication [12,13], which had been based on our investigation on the gelation of chitin with the ionic liquid [14]. In this paper, accordingly, we report the preparation of selfassembled chitin nanofiber (CNF)-reinforced CMC films by the electrostatic interaction on surface of the film according to the procedure in Fig. 2. The morphology and mechanical property of the resulting films were evaluated by the SEM measurement and tensile testing, respectively. The present approach facilely provides new bio-based composite materials from two abundant natural polysaccharides.
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D. Hatanaka et al. / International Journal of Biological Macromolecules 69 (2014) 35–38
Fig. 1. Chemical structures of carboxymethyl cellulose (CMC), chitin, and 1-allyl-3-methylimidazolium bromide (AMIMBr).
2. Experimental part
subsequently under ambient conditions and reduced pressure to give a CMC film.
2.1. Materials Carboxymethyl cellulose (sodium salt, Mw = 7 × 105 , degree of carboxymethylation = 90%) was purchased from Sigma–Aldrich Co. Chitin powder from crab shells was purchased from Wako Pure Chemical Industries, Ltd., Japan. The weight–average molecular weight and degree of deacetylation values of the chitin sample were estimated by viscometric and IR analyses to be 7 × 105 and 4%, respectively [15,16]. An ionic liquid, AMIMBr, was prepared by reaction of 1-methylimidazole with 3-bromo-1-propene according to the method modified from the literature procedure [17]. Other reagents and solvents were available commercially and used without further purification.
2.3. Preparation of self-assembled CNF dispersion A procedure was conducted according to our previous publication [12]. A mixture of chitin (0.12 g, 0.59 mmol) with AMIMBr (1.00 g, 4.92 mmol) was left standing at room temperature for 24 h, followed by heating at 100 ◦ C for 24 h with stirring to give a chitin ion gel with AMIMBr. The gel was then soaked in methanol (40 mL) at room temperature for 48 h, followed by sonication for 10 min to give a self-assembled CNF dispersion (CNF content; 3.0 mg/mL). The dispersion was diluted two and three folds with methanol to give dispersions with 1.5 and 0.75 mg/mL CNF contents, respectively. 2.4. Preparation of chitin nanofiber-reinforced CMC film
2.2. Preparation of CMC film A commercially available CMC sodium salt (0.50 g, 0.24 mmol) was dissolved with water (200 mL) and treated with cationexchange resin (Amberlite IR 120B NA) at room temperature for 5 h. After the resin was removed by filtration, the filtrate was concentrated and thinly casted on a paraffin film. Then, it was dried
A typical experimental procedure was as follows. The CMC film (20.2 mg, 2.1 cm × 1.2 cm) was immersed in 0.75 mg/mL CNF dispersion (5.0 mL, the amount of chitin; 0.019 mmol) and the system was subjected to centrifugation (2000 rpm) for 30 min twice. Then, the film was washed with methanol and dried under reduced pressure to give a CNF-reinforced CMC film.
Fig. 2. Schematic image for preparation procedure of self-assembled CNF-reinforced CMC film.
D. Hatanaka et al. / International Journal of Biological Macromolecules 69 (2014) 35–38
Fig. 3. IR spectra of (a) CMC sodium salt, (b) CMC film, (c) composite film from 3.00 mg/mL CNF dispersion, and (d) chitin powder.
2.5. Measurements Attenuated total reflection (ATR) IR spectra were recorded on a PerkinElmer Spectrum Two spectrometer. Scanning electron microscopy (SEM) images were obtained using an Hitachi SU-70 electron microscope. The stress–strain curves were measured using a tensile tester (Little Senster LSC-1/30, Tokyo Testing Machine). 3. Results and discussion Because CMC is commercially available as its sodium salt form, which shows water solubility, it has been converted into the free acid form for the preparation of the desired CNF/CMC composite film by their electrostatic interaction attributed to the presence of COOH and NH2 groups [18]. After an aqueous solution of the CMC
37
sodium salt was treated with cation-exchange resin, it was thinly casted and dried to give a CMC film having free carboxylic acid groups. The conversion of salt form to acid form was confirmed by the IR analysis. The IR spectrum of the CMC sodium salt showed carbonyl absorption at 1592 cm−1 due to the carboxylate salt (Fig. 3a). The absorption disappeared in the IR spectrum of the resulting film, whereas it newly exhibited carbonyl absorption at 1727 cm−1 due to the carboxylic acid (Fig. 3b). These IR spectra indicated the formation of the CMC film having the carboxylic acid groups. The resulting film showed water insolubility. Then, the self-assembled CNFs were absorbed on surface of the CMC film by the electrostatic interaction to produce the desired composite films. A commercially available chitin powder with degree of deacetylation = 4% was used and the self-assembled CNF dispersions were prepared by soaking chitin/AMIMBr ion gels in methanol, followed by sonication according to the previously reported procedure by us [12]. The aforementioned CMC films were immersed in the dispersions with different CNF contents (0.75, 1.5, and 3.0 mg/mL) (Fig. 2). The systems were subjected to centrifugation and the films were washed with methanol and dried to give the CNF/CMC composite films. The amounts of the absorbed CNFs per unit surface area on the CMC films were calculated by the weight increases of the resulting films from the CMC films used, which increased with increasing the CNF contents in the dispersions as follows; 13.9, 17.5, and 26.5 g/cm2 (CNF/CMC film) from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively. The surface morphologies of the composite films were investigated by the SEM measurement. The SEM images of all the films observed the presence of CNFs on surface of the films (Fig. 4). Furthermore, the images suggested the increases of the number of CNFs on the films with increasing the CNF contents in the dispersions, which were in good agreement with the trend of the CNF amounts determined by the weight calculation as aforementioned. The presence of chitin in the films was also confirmed by the IR measurement because the IR spectra of the resulting films exhibited carbonyl absorption at 1627 cm−1 due to the acetamido group in the chitin structure (Fig. 3d) in addition to that due to the carboxylic acid group, as representatively shown in Fig. 3c. However, the carbonyl absorption due to carboxylate, which took part into the electrostatic interaction with ammonium group, was not detected in the IR spectra. This is probably because of a little presence of the ammonium carboxylate only at the interfacial area between two materials. The mechanical properties of the composite films were evaluated by tensile testing. The stress–strain curves in Fig. 5 indicated obvious increases both in the fracture stress and strain values of the composite films compared with the CMC film. Specifically, the composite film obtained from 3.00 mg/mL CNF dispersion showed the much larger fracture stress and strain values (Fig. 5d) because its surface was largely covered by the CNFs as seen in Fig. 4c. These results strongly suggested the reinforcing effect of the CNFs present even on surface of the films. The previous study also reported the reinforcing effect by the presence of chitin whiskers on surface of a chitosan membrane [19].
Fig. 4. SEM images of (a)–(c) composite films from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively.
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facilely obtained by regeneration from the chitin ion gels, were a good candidate as the material component for the compatibilization with acidic polysaccharides. Therefore, this approach will be applied to other acidic polysaccharides to produce further practical bio-based materials in the future. References
Fig. 5. Stress–strain curves of (a) CMC film and (b)–(d) composite films from 0.75, 1.50, and 3.00 mg/mL CNF dispersions, respectively, under tensile mode; fracture stress and strain values are shown in the figure.
4. Conclusions In this paper, we reported the preparation of the CNF-reinforced CMC films by immersing the CMC films in the CNF dispersions, followed by drying. The amounts of the CNFs on the resulting films increased with increasing the CNF contents in the dispersions used. The SEM images of the films supported the nanofiber morphologies on the films. The reinforcing effect of CNFs present on the films was confirmed by tensile testing and the number of CNFs strongly affected enhancement of the mechanical property. The present study revealed that the self-assembled CNFs, which were
[1] J.M. Berg, J.L. Tymoczko, L. Stryer, Biochemistry, 6th ed., W.H. Freeman & Co., New York, 2006 (Chapter 11). [2] C. Schuerch, in: H.F. Mark, N. Bilkales, C.G. Overberger (Eds.), Encyclopedia of Polymer Science and Engineering, 13, 2nd ed., John Wiley & Sons, New York, 1986, pp. 87–162. [3] A. Rouilly, L. Rigal, J. Macromol, Sci. Polym. Rev C42 (2002) 441–479. [4] A.K. Mohanty, M. Misra, L.T. Drzal, J. Polym. Environ. 10 (2002) 19–26. [5] D. Klemm, B. Heublein, H.P. Fink, A. Bohn, Angew. Chem. Int. Ed. 44 (2005) 3358–3393. [6] D. Klemm, F. Kramer, S. Moritz, T. Lindström, M. Ankerfors, D. Gray, A. Dorris, Angew. Chem. Int. Ed. 50 (2011) 5438–5466. [7] E. Doelker, Adv. Polym. Sci. 107 (1993) 199–265. [8] A.M. Stephen, G.O. Philips, P.A. Williams, Food Polysaccharides and their Applications, Taylor & Francis, London, 1995. [9] K. Kurita, Mar. Biotechnol. 8 (2006) 203–226. [10] M. Rinaudo, Prog. Polym. Sci. 31 (2006) 603–632. [11] C.K.S. Pillai, W. Paul, C.P. Sharma, Prog. Polym. Sci. 34 (2009) 641–678. [12] J. Kadokawa, A. Takegawa, S. Mine, K. Prasad, Carbohydr. Polym. 84 (2011) 1408–1412. [13] R. Tajiri, T. Setoguchi, S. Wakizono, K. Yamamoto, J. Kadokawa, J. Biobased Mater. Bioenergy 7 (2013) 655–659. [14] K. Prasad, M. Murakami, Y. Kaneko, A. Takada, Y. Nakamura, J. Kadokawa, Int. J. Biol. Macromol. 45 (2009) 221–225. [15] M. Poirier, G. Charlet, Carbohydr. Polym. 50 (2002) 363–370. [16] Y. Shigemasa, H. Matsuura, H. Sashiwa, H. Saimoto, Int. J. Biol. Macromol. 18 (1996) 237–242. [17] D. Zhao, Z. Fei, T.J. Geldbach, R. Scopelliti, G. Laurenczy, P.J. Dyson, Helv. Chim. Acta 88 (2005) 665–675. [18] A.M. Bochek, L.D. Yusupova, N.M. Zabivalova, G.A. Petropavlovskii, Russ. J. Appl. Chem. 75 (2002) 645–648. [19] B. Ma, A. Qin, X. Li, X. Zhao, C. He, Mater. Lett. 120 (2014) 82–85.
