Figure 1-1. Nine planetary boundaries as of 2022. The inner dark green shading represents the proposed safe operating space, and the orange wedges represent an estimate of the current position for each boundary. BII,... 42

Figure 1-2. The global flow of plastic packaging in 2013, based on the Project MainStream analysis by World Economic Forum, Ellen MacArthur Foundation & McKinsey & Company (2016). Although energy recovery from... 44

Figure 1-3. Refinery of crustacean shell waste. The shells contain three major chemicals that have many uses. Sustainably refining them can facilitate the growth of the circular bioeconomy. 47

Figure 1-4. The crystal structure of α-chitin and β-chitin. a. View from the bc projection [top of the N-acetylglucosamine (GlcNAc) residue six-membered ring and along the Oa primary axis], which is tilted to clearly... 51

Figure 1-5. Spectroscopic fingerprints of α- and β-chitin. a. In the infrared spectra (1800-1400 cm-1 region) of the two allomorphs, native α-chitin is characterized by a splitting of the amide I (C＝O stretching) vibration into signals...[이미지참조] 54

Figure 1-6. Mechanical properties of nanochitin. a. Ashby plot showing Young's modulus as a function of ultimate tensile strength reported in the literature. b. Qualitative diagram showing the size-cohesion relationship for chitin... 56

Figure 1-7. Hierarchical structure of the lobster cuticle based on Nikolov et al. (2010). Hexagons (yellow) in mineralized chitin-protein fiber planes indicate the honeycomb arrays with a segment length of 200 nm. It should be... 61

Figure 1-8. Optical properties of natural chitinous structures. a. Schematics of chitin nanofibers assembling in a helicoidal plywood (Bouligand) structure that enables structural colors. A left-handed helicoid reflects left-handed... 63

Figure 1-9. Adhesive structures of chitin in nature. Scanning electron microscopic images and schematic showing the spatula- and spindle-like structures found in the terminal elements (circles) of beetle, fly, and spider, indicating... 66

Figure 1-10. Nanoscale interactions of nanochitin. a. Tomography reconstructions and chirality obtained from cryogenic transmission electron microscopic images of an individual chitin nanowhisker (ChNW) based on principal... 69

Figure 1-11. Assembly of chitin nanowhiskers (ChNWs). a. Lyotropic liquid crystalline transition of ChNWs as a function of concentration (wt%). The aqueous suspensions exhibit phase separation on standing, showing a dark,... 71

Figure 1-12. Controlling the performance of nanochitin-reinforced polymer composites. a. Stress-strain curves of chitin nanowhisker (ChNW)/unvulcanized natural rubber composite films obtained by casting-evaporation from... 75

Figure 1-13. Gluing soft, wet substrates with silica nanoparticle suspensions. a. Schematic illustration of the concept of gluing wet polymeric substrates together using nanoparticles. Network chains (blue) are adsorbed on nanoparticles... 78

Figure 1-14. Designing mesoporous silica nanoparticle (MSNP) adhesives. a. Graphical illustration of the hydrogel/tissue polymer interacting on the SNP surface. MSNPs have a larger surface area and higher surface... 82

Figure 1-15. The structure of the guanidino moiety in arginine and its interaction with water. a. Front view of the guanidino (Gd) geometry shows atom labeling according to the IUPAC convention. Geometric values (valence angles... 87

Figure 1-16. Overview of the number of a. scientific publications and b. patents related to nanocellulose and nanochitin research from 1 Jan 2000 to 20 Oct 2022. The scientific publication search was performed using the... 89

Figure 1-17. Thesis structure showing the research packages of this study. The literature review (Chapter 1) provides the context and identifies nanochitin research gaps. Main synthesis and characterization experimental tasks are set... 91

Figure 2-1. Target properties of hydrochloric acid-hydrolyzed chitin nanowhiskers (ChNWs). a. A colloidally stable aqueous ChNW suspension at 1.0 wt%, pH 4.0. a. A scanning electron microscopic image showing the needle-like... 93

Figure 2-2. a. Schematic top-down production of nanochitin through chemical and physical routes into individual nanowhiskers or nanofibers, respectively, accompanied by surface changes. b. The most common laboratory-scale... 95

Figure 2-3. Overview of chemical reactions enabling the post-surface modification of nanochitin, occurring on the amino or hydroxy group, acetamide group, and other functional groups such as carboxylic acid introduced during the... 105

Figure 2-4. Attenuated total reflectance-Fourier-transform infrared spectrum of a. shrimp shell-derived bulk α-chitin (Sigma-Aldrich C7170) compared to those of five nanochitin types including b. chitin nanowhiskers (ChNWs), c.... 109

Figure 2-5. Solid-state ¹³C nuclear magnetic resonance spectrum of bulk chitin (Sigma-Aldrich C7170) compared to those of five nanochitin types including chitin nanowhiskers (ChNWs), TEMPO [(2,2,6,6-tetramethylpiperidin-1-... 112

Figure 2-6. Scanning electron microscopic (SEM) images of five nanochitin types including a. chitin nanowhiskers (ChNWs), b. TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl free radical]-oxidized ChNWs (T-ChNWs),... 115

Figure 2-7. Length and width distributions of five nanochitin types including a. chitin nanowhiskers (ChNWs), b. TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl free radical]-oxidized ChNWs (T-ChNWs), c. zwitterionic ChNWs (Z-ChNWs), d. alkaline deacetylated ChNWs (D-ChNWs), and e. guanylated ChNWs (G-ChNWs). Nanochitin dimensions are... 116

Figure 2-8. X-ray diffractograms (XRDs) of a. bulk α-chitin (Sigma-Aldrich C7170) powder, and freeze-dried powder of five nanochitin types including b. chitin nanowhiskers (ChNWs), c. TEMPO [(2,2,6,6-... 120

Figure 2-9. Photographs of 1.0 wt% aqueous suspensions of five nanochitin types including chitin nanowhiskers (ChNWs), TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical]-oxidized ChNWs (T-ChNWs), zwitterionic... 124

Figure 2-10. Representative conductometric (light gray)/potentiometric (pH, dark gray) titration curves of a. chitin nanowhisker (ChNWs), and b. deacetylated ChNWs (D-ChNWs) showing the graphical determination of equivalent... 130

Figure 2-11. Representative conductometric (light gray)/potentiometric (pH, dark gray) titration curves of a. TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical]-oxidized chitin nanowhiskers (T-ChNWs), and... 132

Figure 2-12. Representative potentiometric (pH) titration curves (blue) and their first derivatives (orange) of a. deacetylated chitin nanowhiskers (D-ChNWs) and b. guanylated ChNWs (G-ChNWs) showing the graphical... 133

Figure 3-1. Schematic illustration of the preparation of nylon 66 (Ny66, gray) nanocomposite films containing cellulose nanocrystals (CNCs, blue) or deacetylated chitin nanowhiskers (D-ChNWs, orange) via a. in situ interfacial... 141

Figure 3-2. Scanning electron microscopic images of executed dumbbell-shaped test specimens, which show the difference in morphology at the grip, whitening (necking), and fractured cross-section positions (Figure 3-4 below)... 145

Figure 3-3. Variation of mechanical properties including Young's modulus (E, ■, blue), ultimate tensile strength (σ, ●, orange), and elongation at break (εb, ▲, gray) with nanofiller content of a. cellulose nanocrystal/nylon 66...[이미지참조] 147

Figure 3-4. a. Photograph and illustration of a nylon 66 film specimen after tensile testing, showing the three regions measured using scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS). SEM images of... 154

Figure 3-5. One-dimensional wide-angle X-ray diffraction patterns and peak deconvolution of a. neat nylon 66, b. in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC0.4), c. in situ polymerized deacetylated chitin... 158

Figure 3-6. Two-dimensional wide-angle X-ray scattering patterns of (from top to bottom) neat nylon 66, in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC0.4), in situ polymerized deacetylated chitin nanowhisker... 159

Figure 3-7. One-dimensional wide-angle X-ray scattering (1D WAXS) patterns of films of a. neat nylon 66 (Ny66), b. in situ polymerized deacetylated chitin nanowhisker (D-ChNW)/Ny66 composite (I-NS0.4), and c. solution... 160

Figure 3-8. Attenuated total reflectance-Fourier-transform infrared spectroscopy (FTIR) spectra in the 1700-1450 cm-1 range showing the amide I and II bands for a. in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC),...[이미지참조] 163

Figure 3-9. Thermal properties of neat nylon 66 (Ny66) and its composite films at 0.4 wt% filler loading. Differential scanning calorimetry (DSC) of a. 1st heating and b. subsequent cooling thermograms of the films: in situ... 166

Figure 3-10. Differential scanning calorimetric (DSC) thermograms showing the (left) 1st heating runs and (right) cooling runs of a. in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC), b. in situ polymerized... 167

Figure 3-11. Thermogravimetric analysis curves of a. in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC), b. in situ polymerized deacetylated chitin nanowhisker (D-ChNW)/nylon 66 (I-NS), c. solution (formic... 170

Figure 3-12. Differential thermogravimetric curves of a. in situ polymerized cellulose nanocrystal (CNC)/nylon 66 (I-NC), b. in situ polymerized deacetylated chitin nanowhisker (D-ChNW)/nylon 66 (I-NS), c. solution (formic... 171

Figure 4-1. Distinguishing different classes of adhesives based on their adhesion principles and features. a. Polymeric tissue adhesives, including chitin hydrogels (Azuma et al., 2015; Pang et al., 2020; Xu et al., 2018).... 180

Figure 4-2. Schematic illustration of various tissue adhesive types and their adhesion strength ranges. Compared to physical adsorption-based nanoparticle suspension adhesives, the performance, storage, and handling of chemically... 181

Figure 4-3. Summary of nanoparticle property. a. Schematic illustrations of dimensions and surface chemistry of bioorganic and TM-50 silica nanoparticles. b. Classifying nanoparticles based on their adhesion abilities (Figure 4-5... 183

Figure 4-4. Amino acid composition (mol%) of (top) porcine skin-derived gelatin and (bottom) porcine skin, grouped based on the propensity of the residue side chain. Tyrosine (Tyr) is considered hydrophobic due to the presence of... 185

Figure 4-5. Adhesion of nanoparticles to soft, wet substrates. a. Representative photographs showing the gluing of two pieces of (left) gelatin hydrogel (23 wt%) and (right) porcine skin using 30 μL of an aqueous suspension of... 187

Figure 4-6. Representative lap shear stress-strain curves of a. gelatin, and b. porcine skin assemblies glued by aqueous suspensions of three groups (Figure 4-3b, 4-5d) of nanoparticles including TM-50 silica nanoparticles... 188

Figure 4-7. Time-dependent adhesion strength of nanoparticle suspensions. Adhesion strengths under normal conditions on a. gelatin hydrogels (23 wt%), and b. porcine skin glued with various aqueous suspensions of... 192

Figure 4-8. Correlation of surface functional group concentration and adhesion strength (τadh) of nanochitin to gelatin hydrogels (23 wt%) by varying a. the [Gd+] of N-guanidinium chitin nanowhiskers (G-ChNWs) and b. the [NH3+]...[이미지참조] 194

Figure 4-9. Dispersion of bioorganic nanoparticles under highly acidic conditions. a. Photographs of the 1.0 wt% aqueous suspensions at pH 2 at 1 h after preparation. CNCs, cellulose nanocrystals; T-ChNWs, TEMPO [(2,2,6,6-... 196

Figure 4-10. Attenuated total reflectance-Fourier-transform infrared spectra of hydrogel substrates including neutral poly(vinyl alcohol) (PVA), anionic polyacrylate (PAA), and cationic poly(allylamine hydrochloride) (PAH) used for... 200

Figure 4-11. a. Attenuated total reflectance-Fourier-transform infrared, and b. ¹H nuclear magnetic resonance spectra of methacryl guanidine hydrochloride (MAGH) monomer used for the synthesis of the guanidinium-... 201

Figure 4-12. Adhesion mechanics of bioorganic nanoparticles at the macroscopic level (bulk adhesion test). (Top) major interactions responsible for the adhesion between functional groups of the nanoparticle (blue) and the hydrogel substrate (orange), and (bottom) adhesion strength of 2 wt % suspensions of bioorganic nanoparticles including cellulose nanocrystals... 203

Figure 4-13. Representative lap shear stress-strain curves of hydrogel assemblies: a. neutral poly(vinyl alcohol) (PVA), b. anionic polyacrylate (PAA), c. cationic poly(allylamine hydrochloride) (PAH), and d. cationic... 204

Figure 4-14. Adhesion mechanics of bioorganic nanoparticles at the molecular level using surface forces apparatus. a. Schematic representation of measuring the surface adhesion showing salt bridge interactions between mica... 205

Figure 4-15. Comparing noncovalent interactions underwater. Linear scale of underwater adhesion energies per unit area in mJ m-2. The energy of the guanidinium (Gd+)-mediated salt bridge in this study is shown along with those of other motifs reported in the literature obtained under aqueous conditions using a surface forces apparatus (Table 4-3). Blue scales...[이미지참조] 209

Figure 4-16. a. Adhesion strengths of aqueous suspensions (2 wt %) of bioorganic nanoparticles including cellulose nanocrystals (CNCs, pH 4), TEMPO [(2,2,6,6-ttetramethylpiperidin-1-yl)oxyl free radical]-oxidized chitin... 211

Figure 4-17. Adhesion strengths of suspensions (2 wt%) of bioorganic nanoparticles including cellulose nanocrystals (CNCs, pH 4), TEMPO [(2,2,6,6-ttetramethylpiperidin-1-yl)oxyl free radical]-oxidized chitin nanowhiskers... 212

Figure 4-18. Wet adhesion and adsorption of nanochitin suspensions (2 wt%, pH 4) to hydrogels. a. The poly(allylamine hydrochloride) (PAH) assembly glued by the zwitterionic chitin nanowhisker (Z-ChNW) suspension... 214

Figure 4-19. Hemostatic properties of nanochitin. a-c. Hemostatic dynamics using dog blood. a. Thromboelastogram demonstrating the development of blood clots and clot strength over time and corresponding... 215

Figure 4-20. Antibacterial activities of bioorganic nanoparticles including cellulose nanocrystals (CNCs), TEMPO [(2,2,6,6-(tetramethylpiperidin-1-yl)oxyl free radical]-oxidized chitin nanowhiskers (T-ChNWs), zwitterionic... 218

Figure 4-21. In vivo biocompatibility testing of N-guanidinium chitin nanowhiskers (G-ChNWs) in a mouse model of asthma induced by ovalbumin (OVA). a. Total and OVA-specific immunoglobulin E (IgE) levels in serums. b. Eosinophil and neutrophil counts in bronchoalveolar lavage fluids (BALF). c. Total immune cell counts in the BALF. Controls... 220

Figure 4-22. In vitro degradation of N-guanidinium chitin nanowhiskers (G-ChNWs) using lysozyme at 37 ℃. a. Weight change after one-week incubation. Phosphate-buffered saline (PBS, 0.1 M, pH 7.4) without lysozyme was... 222

Figure C-1. Representative conductometric (light gray)/potentiometric (pH, dark gray) titration curves of cellulose nanocrystals (CNCs) showing the graphical determination of equivalent points. Blue indicates the equivalence point... 283

Scheme 2-1. Mechanism of acidic hydrolysis of chitin. 99

Scheme 2-2. Mechanism of acidic deacetylation of chitin nanowhiskers. 101

Scheme 2-3. Synthesis of five types of low-aspect ratio nanochitin. Nanochitin having lengths shorter than starting bulk chitin is represented by fewer repeating units. TEMPO, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical.... 108

Scheme 4-1. Synthesis of hydrogel substrates for macroscopic adhesion tests: a. poly(vinyl alcohol) (PVA), b. polyacrylate (PAA), c. poly(allylamine hydrochloride) (PAH), and d. poly(methacryl guanidine hydrochloride)-... 199