**3. CNFs nanocomposites**

Very recently [6] new nanocomposite films of CNFs reinforced silsesquioxane-urethaneacry‐ late (SSQ-UA) copolymer were prepared. CNFs-SSQ-UA nanocomposite films were highly transparent due to filling of nanometer sized (10-20 nm) CNFs inside the hybrid inorganicorganic SSQ-UA copolymer. CNFs due their crystalline structure drastically increased the Young's moduli and the tensile strengths of the composite and decreased the coefficient of thermal expansion (CTE). High thermal stability of polysilsesquioxane improved heat resistance of CNFs. The composite in the ratio of SSQ/UA = 5/0, 4/1, 3/2, 2/3, and 1/4, was prepared and blended with CNFs and copolymerized using a photo initiator 2-Hydroxy-2 methylpropiophenone then cured for free radical polymerization by UV irradiation for 8 min at 40 mW cm-1 (SPOT CURE SP-7, Ushio Inc).

## **3.1. Optical properties of CNFs composites**

Fig. 12 shows % transmittance vs wavelength (nm) of composite film. Neat CNF sheet was not transparent as % transmittance is nil in visible region and interpreted at 600 nm for all composites. While neat poly-SSQ film had approximately 90% transmittance. After SSQ-UA matrix impregnation and subsequent polymerization, the obtained CNFs nanocomposites in different ratio of SSQ/UA became highly transparent for visible light. CNFs sheets blended with SSQ-UA had good transparency (85% at 600 nm) in case of SSQ/UA ratio 5/0. Blending with 1/4 ratio of SSQ/UA, CNFs sheet transparency decreased slightly to 80% compared with 85% for 5/0 blending ratio of SSQ/UA. The composite films became transparent due to nanosized composition of CNF sheet. Since the width (10-20 nm) of CNFs was much shorter than the wavelength of visible light (approximately 400-800 nm), the nanocomposites cause less light scattering than a microfiber reinforced composite at the interface between nanofiber and SSQ-UA matrix. At 600 nm since transmittance of nanocomposites were 85-80%, the optical loss caused by nanofiber reinforcement were only in the range 5-10% despite the high fiber content of 50 wt.%. The transmittance of nanocomposites increased as ratio of SSQ increased. The chitin nanofiber sheet obtained in this study can be available like a paper, though the novelty of the paper is composed of nano-meter thick fibers. Several patterns can be printed on the nanofiber paper that we have prepared using a domestic inkjet printer (Fig. 13a). The printed NF paper became transparent (Fig. 13b) after matrix impregnation. This newly established technique of transparent printing on such a thin (70 µm) composite sheet can have application in printing of wiring used in electronic devices or electronic papers.

81% decreased compared to the corresponding to neat SSQ-UA matrices. Thus, CNFs with low CTE worked effectively to decrease the thermal expansion of SSQ-UA copolymer film as a

**Figure 13.** CNFs sheet a) without blending with SSQ-UA matrix; b) after blending with SSQ-UA matrix followed by

copolymerization by UV irradiation. Reproduced with permission from ref. 6. Copyright 2012, Elsevier.

**Figure 12.** Regular light transmittance spectra of CNFs composite film, the material of which measurements were con‐

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ducted are shown in the inset of figure. Reproduced with permission from ref. 6. Copyright 2012, Elsevier.

Fig. 15 shows Young's moduli and tensile strengths of SSQ-UA copolymer films and their CNFs composites. The Young's moduli of SSQ-UA with the ratio of 3/2, 2/3, and 1/4 without CNFs decreased from 1,571 to 128 MPa with increasing the ratio of reactive diluent UA oligomer. This is due to decrease in crosslinking density with decreasing the amount of strengthening hybrid component SSQ. The SSQ-UA films with the ratio of 5/0 and 4/1 were too fragile to measure the mechanical properties so their bars are not shown in the Young's

result of reinforcement.

**3.3. Mechanical characterization of composites**

#### **3.2. Thermal properties of composites**

Fig. 14 shows the CTE of neat CNFs and its composites. Although neat poly-SSQ (SSQ/UA = 5/0) was too fragile to measure the thermal expansion, the CNF reinforced nanocomposite was tough for CTE measurement. CTE of CNF sheet without SSQ matrix was only 8.0 × 10-6 K-1. While CTE of SSQ-UA copolymer films without CNFs were high in the range 96.2-164.0 × 10-6 K-1 depending on the ratio of SSQ/UA as shown by bars in Fig. 14. CTEs of all nanocomposites decreased significantly to a constant value of 30 × 10-6 K-1. These values corresponded to 66 to

**Figure 12.** Regular light transmittance spectra of CNFs composite film, the material of which measurements were con‐ ducted are shown in the inset of figure. Reproduced with permission from ref. 6. Copyright 2012, Elsevier.

**Figure 13.** CNFs sheet a) without blending with SSQ-UA matrix; b) after blending with SSQ-UA matrix followed by copolymerization by UV irradiation. Reproduced with permission from ref. 6. Copyright 2012, Elsevier.

81% decreased compared to the corresponding to neat SSQ-UA matrices. Thus, CNFs with low CTE worked effectively to decrease the thermal expansion of SSQ-UA copolymer film as a result of reinforcement.

#### **3.3. Mechanical characterization of composites**

**3. CNFs nanocomposites**

96 Advances in Nanofibers

at 40 mW cm-1 (SPOT CURE SP-7, Ushio Inc).

**3.1. Optical properties of CNFs composites**

**3.2. Thermal properties of composites**

Very recently [6] new nanocomposite films of CNFs reinforced silsesquioxane-urethaneacry‐ late (SSQ-UA) copolymer were prepared. CNFs-SSQ-UA nanocomposite films were highly transparent due to filling of nanometer sized (10-20 nm) CNFs inside the hybrid inorganicorganic SSQ-UA copolymer. CNFs due their crystalline structure drastically increased the Young's moduli and the tensile strengths of the composite and decreased the coefficient of thermal expansion (CTE). High thermal stability of polysilsesquioxane improved heat resistance of CNFs. The composite in the ratio of SSQ/UA = 5/0, 4/1, 3/2, 2/3, and 1/4, was prepared and blended with CNFs and copolymerized using a photo initiator 2-Hydroxy-2 methylpropiophenone then cured for free radical polymerization by UV irradiation for 8 min

Fig. 12 shows % transmittance vs wavelength (nm) of composite film. Neat CNF sheet was not transparent as % transmittance is nil in visible region and interpreted at 600 nm for all composites. While neat poly-SSQ film had approximately 90% transmittance. After SSQ-UA matrix impregnation and subsequent polymerization, the obtained CNFs nanocomposites in different ratio of SSQ/UA became highly transparent for visible light. CNFs sheets blended with SSQ-UA had good transparency (85% at 600 nm) in case of SSQ/UA ratio 5/0. Blending with 1/4 ratio of SSQ/UA, CNFs sheet transparency decreased slightly to 80% compared with 85% for 5/0 blending ratio of SSQ/UA. The composite films became transparent due to nanosized composition of CNF sheet. Since the width (10-20 nm) of CNFs was much shorter than the wavelength of visible light (approximately 400-800 nm), the nanocomposites cause less light scattering than a microfiber reinforced composite at the interface between nanofiber and SSQ-UA matrix. At 600 nm since transmittance of nanocomposites were 85-80%, the optical loss caused by nanofiber reinforcement were only in the range 5-10% despite the high fiber content of 50 wt.%. The transmittance of nanocomposites increased as ratio of SSQ increased. The chitin nanofiber sheet obtained in this study can be available like a paper, though the novelty of the paper is composed of nano-meter thick fibers. Several patterns can be printed on the nanofiber paper that we have prepared using a domestic inkjet printer (Fig. 13a). The printed NF paper became transparent (Fig. 13b) after matrix impregnation. This newly established technique of transparent printing on such a thin (70 µm) composite sheet can have

application in printing of wiring used in electronic devices or electronic papers.

Fig. 14 shows the CTE of neat CNFs and its composites. Although neat poly-SSQ (SSQ/UA = 5/0) was too fragile to measure the thermal expansion, the CNF reinforced nanocomposite was tough for CTE measurement. CTE of CNF sheet without SSQ matrix was only 8.0 × 10-6 K-1. While CTE of SSQ-UA copolymer films without CNFs were high in the range 96.2-164.0 × 10-6 K-1 depending on the ratio of SSQ/UA as shown by bars in Fig. 14. CTEs of all nanocomposites decreased significantly to a constant value of 30 × 10-6 K-1. These values corresponded to 66 to Fig. 15 shows Young's moduli and tensile strengths of SSQ-UA copolymer films and their CNFs composites. The Young's moduli of SSQ-UA with the ratio of 3/2, 2/3, and 1/4 without CNFs decreased from 1,571 to 128 MPa with increasing the ratio of reactive diluent UA oligomer. This is due to decrease in crosslinking density with decreasing the amount of strengthening hybrid component SSQ. The SSQ-UA films with the ratio of 5/0 and 4/1 were too fragile to measure the mechanical properties so their bars are not shown in the Young's

**4. Preventive effect of CNF on dextran sulfate sodium (DSS)-induced**

In this section we describe the medical aspect of CNFs taking a model of DSS- induced colitis in mouse as investigated by Azuma et al [4]. The effect of CNFs on disease activity index such as weight loose, loose stools, and bleeding symptoms in colitis were studied. CNFs adminis‐ tered mouse exhibited a significant reduced in disease activity index. Colon length increased that was shortened due to DSS induction by administration of CNFs compared to control. Damage in intestinal mucosa was microscopically monitored as shown in Fig. 16. In CNFs group on 6th day erosion, crypt destruction, and edema were markedly suppressed compared to control. The number of myeloperoxidase (MPO)-positive cells lowered significantly compared to control group. Thus CNFs improved clinical symptoms in DSS-induced acute UC

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**Figure 16.** Effect of CNFs administration on histopathologicucedal changes in DSS-induced acute UC mice; a) control,

Preparation of CNFs from crab, prawn shells, and a number of species of mushrooms have been discussed. Both chemical treatments and mechanical processing have been described in detail. CNFs prepared from crab shell, the presence of acidic medium was important to reduce the size of NFs. While in case of prawn shells the fibrillation was achieved in neutral conditions. Width of CNFs was 10-20 nm with high aspect ratio. After completion of fibrillation the CNFs were in physical state of wet gel of very high viscosity. Size of NFs was determined by recording FE-SEM of flakes or thin film of NFs. Apart from using grinder a newly developed high pressure jet atomization machine (Star Burst System; SBS) was also employed to fibrillate the NFs. Fibrillation was more effective when SBS was used that gave more thinner (19.0-16.5 nm) and homogeneous NFs compared to girder. NFs were characterized for chitin content by XRD and FT-IR measurements. CNFs were also prepared from five different species of edible

b) CNFs, and c) chitin powder. Reproduced with permission from ref. 4. Copyright 2012, Elsevier.

**ulcerative colitis (UC)**

mouse model.

**5. Conclusion**

**Figure 14.** Coefficient of thermal expansion (CTE) of SSQ-UA copolymer films and SSQ-UA-CNFs composites. Repro‐ duced with permission from ref. 6. Copyright 2012, Elsevier.

moduli plot. Nanocomposites were tough enough for the testing due to CNF support. The Young's moduli of these nanocomposites significantly increased and reached in the range 3.36 to 4.29 GPa. The tensile strengths also significantly increased in the range 31 to 59 MPa. It is important to notice that each Young's moduli and tensile strength of the chitin nanofiber composites were higher than that of CNF sheet or SSQ-UA copolymer. The higher Young's moduli and tensile strength of composite is due to SSQ-UA matrix embedded in every space of CNF sheet and strongly interacts with NF at the interface thus resulted in the increase of the reinforcement effect. The enhancements of mechanical properties of composite strongly support that a CNF sheet with a high Young's modulus (1.80 GPa) and a high tensile strength (30 MPa) worked effectively as a reinforcement filler for SSQ-UA copolymer.

**Figure 15.** Young's modulus and tensile strength of SSQ-UA copolymer and SSQ-UA-CNFs composites. Reproduced with permission from ref. 6. Copyright 2012, Elsevier.
