Estimating the Strength of Single Chitin Nanofibrils via Sonication

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Estimating The Strength of Single Chitin Nanofibrils via Sonication-Induced Fragmentation Yu Bamba, Yu Ogawa, Tsuguyuki Saito, Lars A. Berglund, and Akira Isogai Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.7b01467 • Publication Date (Web): 14 Nov 2017 Downloaded from http://pubs.acs.org on November 16, 2017

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Estimating The Strength of Single Chitin Nanofibrils via Sonication-Induced Fragmentation Yu Bamba,† Yu Ogawa,‡,§ Tsuguyuki Saito,†,* Lars A. Berglund,# and Akira Isogai† †

Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The

University of Tokyo, Tokyo 113-8657, Japan ‡

CERMAV, University of Grenoble Alpes, F-38000 Grenoble, France

§

CERMAV, CNRS, F-38000 Grenoble, France

#

Wallenberg Wood Science Center and Department of Fibre and Polymer Technology, Royal

Institute of Technology, SE-100 44 Stockholm, Sweden

ABSTRACT: We report the mechanical strength of native chitin nanofibrils. Highly crystalline α-chitin nanofibrils were purified from filaments produced by a microalgae Phaeocystis globosa, and two types of β-chitin nanofibrils were purified from pens of a squid Loligo bleekeri and tubes of a tubeworm Lamellibrachia satsuma, with relatively low and high crystallinity, respectively. These chitin nanofibrils were fully dispersed in water. Strength of individualized nanofibrils was estimated using cavitation-induced tensile fracture of nanoscale filaments in a liquid medium. Both types of β-chitin nanofibrils exhibited similar strength values of approximately 3 GP; in contrast, the α-chitin nanofibrils exhibited a much lower strength value

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of 1.6 GPa. These strength estimates suggest that the tensile strength of chitin nanofibrils is governed by the molecular packing modes of chitin, rather than their crystallinity. KEYWORDS: chitin, strength, nanofibril, sonication, cavitation

INTRODUCTION Nanofibrillar native chitin is an emerging bio-based material that combines biochemical functions and good mechanical properties.1-2 Potential applications include wound dressings and substrates for cell culture. The elastic moduli of single chitin nanofibrils have previously been measured,3-5 but their mechanical strength has not been examined. Thus, it still remains an important subject for both the fundamental understanding and application of chitin. The lack of experimental analyses on single nanofibril strength is likely because of the technical difficulties of nanoscale mechanics and dispersing biologically-structured chitin nanofibrils, which are strongly linked via proteins and minerals in living tissues.6-7 However, several approaches to disintegrating chitin into individual nanofibrils have recently been proposed.8-14 We report the strength of individualized chitin nanofibrils estimated using cavitationinduced tensile fracture of nanoscale filaments in a liquid medium.15-17 This strength estimate approach was experimentally validated using carbon nanotubes and protein fibrils,15 and has also been applied to cellulose nanofibrils.18 Essentially, the strength of nanoscale filaments was calculated from the final invariable length and cross-sectional area of filaments that were sufficiently fragmented in a liquid medium, using an ultrasonic homogenizer. The implosion dynamics of cavitation bubbles were assumed as follows (see Reference 15 for theoretical details and experimental validation). An imploding bubble of the radius and wall velocity induces a radial solvent flow into the cavity center, with an inverse square dependence of the flow


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velocity on the distance from the cavity center ( = / ), so that the filaments in the vicinity of an imploding cavity are pulled toward the center by the gradient solvent flow, or tensile stress is imposed on the filaments. The maximum tensile stress is generated when the cavity is minimum in size (~10 µm), one end of the filament is positioned in the immediate vicinity of the cavity, and the filament is oriented to the radial solvent flow into the cavity center. This tensile stress is strong enough to break carbon nanotubes, and any filaments are fragmented at the initial stage of sonication treatment. After a sufficiently long time of ultrasonic treatment, the fragmented filaments have invariable lengths, called limiting length , at which tensile stress becomes equal to strength .

For filaments with circular or square cross sections, the strength was as follows,15

2 = (1)

where is the viscosity of solvent, and is the diameter or width of the filament. This equation

was simplified by applying a typical value / ~10 s , and using ~10 Pa s of water, ≈ 2 × 10! "

# (2)

For filaments with rectangular cross sections, the strength was as follows, =

1 1 $ + ( (3) % '

where % and ' are the width and thickness of the rectangular cross section, respectively. The equation was simplified in the same manner as Equation 2, 1 1 ≈ 1.0 × 10! $ + ( (4) % '


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EXPERIMENTAL SECTION Materials. Squid-pen β-chitin was purified from Loligo bleekeri pens. Pens were cut into 1 cm pieces, and soaked in a 2:1 mixture of CHCl3 and CH3OH for 1 d to extract lipids and lipoproteins. Pens were then sequentially treated with a 2.5 M NaOH solution, a 0.3% NaClO2 solution, and a 1 M HCl solution. This sequential process was repeated four times to purify βchitin. The NaOH treatment was carried out for 1 d under a nitrogen purge; the NaClO2 treatment was carried out for 3 h in an acetate buffer adjusted at pH 4.8 and at 70 °C; and the HCl treatment was carried out for 3 h. Tubeworm β-chitin was purified from tubes of Lamellibrachia satsuma. Tubes were cut into 1 cm pieces, and purified in the same manner as squid-pen chitin. Purified tubeworm chitin was surface-modified by TEMPO-mediated oxidation with 10 mmol NaClO per gram of chitin,10 and washed with deionized water. Algal α-chitin was purified from Phaeocystis globosa filaments. The filaments were purified in the same manner as squid-pen chitin. All purified chitins were kept in a wet state until use. All chemicals were laboratory grade (Wako Pure Chemicals, Tokyo, Japan) and used as received. Sonication. Squid pen and algal chitins were suspended in acetic acid solutions with pH 3.3 at 0.01% w/v.8,

19

Tubeworm chitin was suspended in distilled water at 0.01% w/v. Chitin

suspensions (20 mL) were roughly homogenized using a Physcotron NS-56 at 7500 rpm for 1min, and then sonicated using a Nihon Seiki US-300T (300W, 19.5 kHz) operating at 6% output power. The ultrasonic waves were emitted in a 5 min on/5 min off interval for up to 400 min, while the temperature of the suspension was maintained at approximately 10 °C using a cooling system. Analyses. X-ray diffraction data of squid-pen and tubeworm β-chitins were collected at BL40B2 of SPring-8 (Hyogo, Japan). Diffraction patterns were recorded using a flat imaging


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plate (Rigaku, Tokyo, Japan). Crystal sizes of the hydrated (0 1 0) plane were calculated using Scherrer’s equation,20 being regarded as and ' of squid-pen and tubeworm β-chitins, respectively. The line broadening of diffraction peaks were estimated via peak deconvolution using pseudo-Voigt functions. TEM observations were performed using a JEOL JEM-2000EX microscope, operated at an accelerating voltage of 200 kV. The 0.01% suspensions were diluted to 0.0005% with an acetic acid solution at pH 3.3 or distilled water, and negatively stained with a 0.5% uranyl acetate solution. For each chitin sample, the length of approximately 200 chitin nanofibrils were measured from TEM images using an image processing software. The widths

and % of tubeworm and algal nanofibrils, respectively, were also measured by TEM.

RESULTS AND DISCUSSION Length of Fragmented Nanofibrils. We used three kinds of chitin, purified from pens of a squid L. bleekeri, tubes of a tubeworm L. satsuma, and filaments produced by a microalgae Phaeocystis globosa. Squid-pen chitin has the crystal form of β-chitin, and consists of relatively low-crystallinity nanofibrils a few nm in width. Tubeworm chitin also has the crystal form of βchitin, but consists of highly crystalline nanofibrils with widths of 20–50 nm. Algal chitin has the crystal form of α-chitin, and its nanofibrils are highly crystalline. The cross sectional shape of squid-pen, tubeworm, and algal chitin nanofibrils were assumed to square, rectangle, and circle, respectively (Figure 1).21-22 Although shells of crabs and shrimps are abundant and widely used as chitin resources, their nanofibrils were not individually dispersed, and therefore, were unable to be used in this study. a)

b) d

dW

c) d

dT


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Figure 1. The approximated shapes of (a) squid pen, (b) tubeworm, and (c) algal chitin nanofibril cross-sections.

Figure 2. TEM images and length distributions of squid-pen chitin nanofibrils sonicated for (a,b) 5 min, (c) 80 min, and (d,e) 400 min.


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The squid-pen nanofibrils were fully individualized by sonication within the initial 5 min (Figure 2a). The nanofibrils were long, and those with lengths greater than 1 µm were often observed, but included some kinks (Figure 2b). After 80 min of sonication, most of the nanofibrils were significantly fragmented, and the average length was reduced to approximately 480 nm (Figure 2c). Further sonication up to 400 min did not markedly change nanofibril morphology (Figure 2d,e). The average length of the nanofibrils was still approximately 450 nm, and their length distribution was nearly unchanged from that of the nanofibrils sonicated for 80 min (Figure 2c,e). These result indicate that the nanofibrils were subjected to the maximum tensile load (see Introduction section), and sufficiently fragmented overcoming the stochastic nature of cavitation-induced fragmentation. Therefore, the length distribution extending asymmetrically is likely to come from the inherent structure of chitin nanofibrils. The time limiting length is achieved depends only on sonication parameters such as pulsing rate, power, and container geometry;15 in fact, our sonication conditions were sufficient for reaching the limiting length of chitin nanofibrils. Thus, we sonicated the other samples for up to 400 min under the same conditions. Tubeworm chitin was not dispersed under the same sonication conditions as those applied for the squid-pen sample. This was probably because the degree of N-acetylation of tubeworm chitin was very high (0.99),10 and the amount of electric charges required for dispersion was not enough. Therefore, it was TEMPO-oxidized before sonication, and nanofibril surfaces were partially carboxylated. Accordingly, the carboxylated tubeworm nanofibrils were readily dispersed by sonication for 5 min (Figure 3a). Tubeworm nanofibrils were very long, and most were greater than 5 µm in length. After 400 min of sonication, the average length of tubeworm nanofibrils was reduced to approximately 2 µm (Figure 3b). The distribution of both the length


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and width of the tubeworm nanofibrils were wide, and no significant correlation between length and width was found (Figure 3c). Although a few nm-wide thin fibrils were occasionally found with TEM, these fibrils had no clear particle boundary and were not included in the results.

Figure 3. TEM images and length distributions of (a‒c) tubeworm and (d‒f) algal chitin nanofibrils sonicated for (a,d) 5 min and (b,e) 400 min.


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Algal nanofibrils were dispersed by sonication for 5 min and were long, similar to tubeworm nanofibrils (Figure 3d). After 400 min of sonication, the average length was reduced to approximately 3 µm (Figure 3e). The size distribution of algal nanofibrils was also wide, and no significant correlation between length and width was found (Figure 3f). Width of Fragmented Nanofibrils. The crystal lattice of β-chitin takes on the hydrated form in the presence of water.23 Water molecules are intercalated within the (0 1 0) plane of βchitin, expanding the cross-sectional sizes of β-chitin nanofibrils. Sonication-induced fragmentation occurs in water, and hydration should be accounted for estimating squid-pen and tubeworm nanofibril cross-sections. Thus, cross-sectional dimensions d and dT of squid-pen and tubeworm nanofibrils (see Figure 1) were approximated to crystal sizes of the (0 1 0) plane of wet β-chitin samples (Figure 4), and were approximately 4 and 17 nm, respectively. According to a previous study on the packing mode of the crystal lattice in cross-sections of tubeworm βchitin nanofibril, cross-sectional dimensions dW of tubeworm nanofibrils do not change in water;21 the crystallite size normal to hydrated (0 1 0) plane corresponds to the short side of the rectangular cross section, and the long side that is along (0 1 0) plane does not expand in water. Thus, the dW values were measured as the nanofibril widths using TEM. It is probable that the nanofibril widths shown in TEM images were the long sides, because tubeworm nanofibrils were likely deposited on the hydrophilic TEM grid with their long sides down. The α-chitin crystals are not hydrated, and the cross-sectional dimensions d of algal α-chitin nanofibrils were determined using TEM. For all chitin samples, nanofibril widths were roughly unchanged before and after sonication.


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Squid pen (0 1 0)

dry

wet

Intensity (a.u.)

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Tubeworm (0 1 0)

dry

wet

0.4

0.8

1.2

1.6

2.0

-1

q, 2π/d (Å )

Figure 4. X-ray diffraction profiles of squid-pen and tubeworm β-chitin nanofibrils in dry and wet states.

Strength Estimates. Figure 5 shows the strength distributions of squid-pen, tubeworm, and algal chitin nanofibrils, which were estimated by substituting the length and width of sonicated (400 min) nanofibrils for and values, respectively, in Equation 2 (squid pen and algae) or


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Equation 4 (tubeworm). Table 1 summarizes mean strength values. Similar to cellulose nanofibrils,18 all chitin nanofibrils showed asymmetrically extended distributions of strength, so that the geometric means were significantly lower than their arithmetic means.

30

30

a)

30

b)

20 15 10 5

20 15 10 5

0 1

2

3

4

5

6

7

8

20 15 10 5

0 0

c)

25

Frequency (%)

25

Frequency (%)

25

Frequency (%)

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0 0

1

Strength (GPa)

2

3

4

5

6

7

8

0

1

Strength (GPa)

2

3

4

5

6

7

8

Strength (GPa)

Figure 5. Strength distributions of (a) squid-pen, (b) tubeworm, and (c) algal chitin nanofibrils.

Table 1. Summary of Strength Estimates of Chitin Nanofibrils. cross-sectional dimension (nm)

limiting length

sample

tensile strength σ

d

dW

dT

Llim (nm)

AMa (GPa)

GMb (GPa)

GSDc

squid-pen β-chitin

4.1

–

–

452 ± 235

3.1

1.9

2.9

tubeworm β-chitin

–

38 ±10

17

2179 ± 1398

2.8

1.3

3.9

–

–

2904 ± 1727

1.6

0.9

3.2

algal α-chitin a

37 ± 8 b

c

Arithmetic mean, Geometric mean, Geometric standard deviation.

Both β-chitin nanofibrils exhibited similar strength of approximately 3 GPa in arithmetic mean, irrespective of crystallinity. This suggests that the strength of these chitin nanofibrils is predominantly based on the breaking strength of covalent bonds along chitin molecular chains, rather than those of hydrogen bonds or other van der Waals interactions. Accordingly, β-chitin nanofibrils can mechanically function to their full extent, considering the theoretical assumption


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that the ideal strength of solids is approximately one fifteenth of the elastic modulus;24 the strength (3 GPa) was very close to one fifteenth of the elastic modulus of β-chitin (~40 GPa).5 The α-chitin nanofibrils of algae exhibited a much lower mean strength value (1.6 GPa in arithmetic mean), despite their high crystallinity. The strength of α-chitin is about half that of βchitin, even though α-chitin (1.46 g cm-3) is anhydrate and slightly higher in density than hydrated β-chitin (1.43 g cm-3).23, 25 Further, this strength value was significantly lower than one fifteenth of the elastic modulus of α-chitin (~60 GPa).4 The difference in strength between α- and β-chitin nanofibrils may be due to their molecular packing modes;25-26 α-chitin has an antiparallel packing mode where the reducing ends of neighboring molecular chains point in opposite directions, whereas β-chitin has a parallel packing mode where the reducing ends of all molecular chains point in the same direction. The anti-parallel packing mode is likely to make it more difficult to continue the crystal phase in the direction of the fiber axis during biosynthesis, introducing more defects. Figure 6 shows Weibull plots constructed from strength distributions using the following equation,27 3 ,() = exp 0− " # 4 (5) 2

where ,() is the probability of a nanofibril remaining unbroken at a given load , and the

parameters 2 and 6 are adjustable constants. Parameter 2 is the mean strength value. Parameter 6 is given as the slope of the Weibull plot, and related to the coefficient of variation.

Materials with large variability in strength have smaller 6 values. For example, in regular tensile

tests, steel 6 is approximately 100, whereas more brittle ceramics 6 is approximately 10. In this

study, the resulting 6 values were very small and approximately 1.1, 0.9, and 1.1 for the squid-

pen, tubeworm, and algal nanofibrils, respectively. Although these 6 values cannot be directly


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compared with those from regular tensile tests of large, hand-holdable specimens, it should be noted that the 6 values of all chitin nanofibrils were approximately 1, and were almost the same values as those for cellulose nanofibrils using the same sonication method.18 This consistency possibly suggests high defect-dependency of nanofibrillar structure consisting of oriented molecular chains on tensile strength, for both chitin and cellulose.

2

0

ln[-ln(P)]

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-2

-4

Algae Tubeworm Squid pen

-6 -4

-2

0

2

4

ln(σ)

Figure 6. Weibull plots constructed from strength distributions in Figure 5.

CONCLUSIONS The strength values of 1) a few nm-wide and relatively low crystalline squid-pen β-chitin nanofibrils, 2) thick and highly crystalline tubeworm β-chitin nanofibrils, and 3) thick and highly crystalline algal α-chitin, were experimentally estimated on the basis of cavitation-induced tensile fracture of nanofibrils in water. Both types of β-chitin nanofibrils exhibited similar strength of approximately 3 GP; whereas, the α-chitin nanofibrils of algae exhibited a much lower strength of 1.6 GPa. These estimates suggest that the tensile strength of chitin nanofibrils


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is governed by the molecular packing modes of chitin, rather than cross-sectional dimensions and crystallinity. The strength values presented here are comparable to those of cellulose nanofibrils, which is reasonable because chitin is similar to cellulose in both molecular structure and packing mode. Indeed, nanofibrillar native chitin is a unique material exhibiting high mechanical strength, as well as biochemical functions for medical applications.

AUTHOR INFORMATION Corresponding Author * [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This study was partially supported by Grants-in-Aid for scientific research from the Japan Society for the Promotion of Science (JSPS, 15H04524 and 15K14765), the Core Research for Evolutional Science and Technology (CREST, JPMJCR13B2) and the Mirai programs of the Japan Science and Technology Agency (JST). The authors are grateful to Dr. Masahisa Wada (Kyoto University, Japan) and Dr. Satoshi Kimura (The University of Tokyo, Japan) for kindly providing us with tubeworm and algal chitin samples.

REFERENCES 1. Rinaudo, M. Chitin and chitosan: Properties and applications. Prog. Polym. Sci. 2006, 31, 603‒632.


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2. Ifuku, S.; Saimoto, H. Chitin nanofibers: preparations, modifications, and applications. Nanoscale 2012, 4, 3308‒3318. 3. Nishino, T.; Matsui, R.; Nakamae, K. Elastic modulus of the crystalline regions of chitin and chitosan. J. Polym. Sci. Pol. Phys. 1999, 37, 1191‒1196. 4. Ogawa, Y.; Hori, R.; Kim, U. J.; Wada, M. Elastic modulus in the crystalline region and the thermal expansion coefficients of α-chitin determined using synchrotron radiated X-ray diffraction. Carbohydr. Polym. 2011, 83, 1213‒1217. 5. Moshe-Drezner, H.; Shilo, D.; Dorogoy, A.; Zolotoyabko, E. Nanometer-Scale Mapping of Elastic Modules in Biogenic Composites: The Nacre of Mollusk Shells. Adv. Funct. Mater. 2010, 20, 2723‒2728. 6. Nikolov, S.; Petrov, M.; Lymperakis, L.; Friak, M.; Sachs, C.; Fabritius, H. O.; Raabe, D.; Neugebauer, J. Revealing the Design Principles of High-Performance Biological Composites Using Ab initio and Multiscale Simulations: The Example of Lobster Cuticle. Adv. Mater. 2010, 22, 519‒526. 7. Chaussard, G.; Domard, A. New aspects of the extraction of chitin from squid pens. Biomacromolecules 2004, 5, 559‒564. 8. Fan, Y. M.; Saito, T.; Isogai, A. Preparation of chitin nanofibers from squid pen β-chitin by simple mechanical treatment under acid conditions. Biomacromolecules 2008, 9, 1919‒1923. 9. Fan, Y.; Saito, T.; Isogai, A. Chitin nanocrystals prepared by TEMPO-mediated oxidation of α-chitin. Biomacromolecules 2008, 9, 192‒198. 10. Fan, Y. M.; Saito, T.; Isogai, A. TEMPO-mediated oxidation of β-chitin to prepare individual nanofibrils. Carbohydr. Polym. 2009, 77, 832‒838. 11. Fan, Y. M.; Saito, T.; Isogai, A. Individual chitin nano-whiskers prepared from partially deacetylated α-chitin by fibril surface cationization. Carbohydr. Polym. 2010, 79, 1046‒1051. 12. Ifuku, S.; Nogi, M.; Abe, K.; Yoshioka, M.; Morimoto, M.; Saimoto, H.; Yano, H. Preparation of Chitin Nanofibers with a Uniform Width as α-Chitin from Crab Shells. Biomacromolecules 2009, 10, 1584‒1588. 13. Ifuku, S.; Nogi, M.; Yoshioka, M.; Morimoto, M.; Yano, H.; Saimoto, H. Fibrillation of dried chitin into 10-20 nm nanofibers by a simple grinding method under acidic conditions. Carbohydr. Polym. 2010, 81, 134‒139. 14. Ifuku, S.; Nogi, M.; Abe, K.; Yoshioka, M.; Morimoto, M.; Saimoto, H.; Yano, H. Simple preparation method of chitin nanofibers with a uniform width of 10-20 nm from prawn shell under neutral conditions. Carbohydr. Polym. 2011, 84, 762‒764. 15. Huang, Y. Y.; Knowles, T. P. J.; Terentjev, E. M. Strength of Nanotubes, Filaments, and Nanowires From Sonication-Induced Scission. Adv. Mater. 2009, 21, 3945‒3948. 16. Hennrich, F.; Krupke, R.; Arnold, K.; Stutz, J. A. R.; Lebedkin, S.; Koch, T.; Schimmel, T.; Kappes, M. M. The mechanism of cavitation-induced scission of single-walled carbon nanotubes. J. Phys. Chem. B 2007, 111, 1932‒1937. 17. Rooze, J.; Groote, R.; Jakobs, R. T. M.; Sijbesma, R. P.; van Iersel, M. M.; Rebrov, E. V.; Schouten, J. C.; Keurentjes, J. T. F. Mechanism of Ultrasound Scission of a Silver-Carbene Coordination Polymer. J. Phys. Chem. B 2011, 115, 11038‒11043. 18. Saito, T.; Kuramae, R.; Wohlert, J.; Berglund, L. A.; Isogai, A. An Ultrastrong Nanofibrillar Biomaterial: The Strength of Single Cellulose Nanofibrils Revealed via SonicationInduced Fragmentation. Biomacromolecules 2013, 14, 248‒253.


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19. Qi, Z. D.; Fan, Y. M.; Saito, T.; Fukuzumi, H.; Tsutsumi, Y.; Isogai, A. Improvement of nanofibrillation efficiency of α-chitin in water by selecting acid used for surface cationisation. RSC Adv. 2013, 3, 2613‒2619. 20. Alexander, L. E. X-ray Diffraction Methods in Polymer Science. Robert E. Kreiger Publishing Co.: Huntington, NY, 1979. 21. Ogawa, Y.; Kimura, S.; Wada, M. Electron diffraction and high-resolution imaging on highly-crystalline β-chitin microfibril. J. Struct. Biol. 2011, 176, 83‒90. 22. Ogawa, Y.; Kimura, S.; Wada, M.; Kuga, S. Crystal analysis and high-resolution imaging of microfibrillar α-chitin from Phaeocystis. J. Struct. Biol. 2010, 171, 111‒116. 23. Kobayashi, K.; Kimura, S.; Togawa, E.; Wada, M. Crystal transition between hydrate and anhydrous β-chitin monitored by synchrotron X-ray fiber diffraction. Carbohydr. Polym. 2010, 79, 882‒889. 24. Ashby, M.; Shercliff, H.; Cebon, D. Materials: Engineering, Science, Processing and Design. Butterworth-Heinemann: Oxford, 2009. 25. Sikorski, P.; Hori, R.; Wada, M. Revisit of α-Chitin Crystal Structure Using High Resolution X-ray Diffraction Data. Biomacromolecules 2009, 10, 1100‒1105. 26. Nishiyama, Y.; Noishiki, Y.; Wada, M. X-ray Structure of Anhydrous β-Chitin at 1 angstrom Resolution. Macromolecules 2011, 44, 950‒957. 27. Roylance, D. Mechanics of Materials. John Wiley & Sons: New York, 1996; p 251‒254.


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For Table of Contents Use Only Estimating The Strength of Single Chitin Nanofibrils via Sonication-Induced Fragmentation Yu Bamba, Yu Ogawa, Tsuguyuki Saito, Lars A. Berglund, and Akira Isogai


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Estimating the Strength of Single Chitin Nanofibrils via Sonication

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