Individualization of nano-sized plant cellulose fibrils

Transcription

1 Individualization of nano-sized plant cellulose fibrils achieved by direct surface carboxylation using TEMP catalyst Department of Biomaterial Sciences The University of Tokyo Akira ISGAI

2 TEMP / NaBr / NaCl oxidation of polysaccharides at ph 10 Advantages points : Aqueous media at ph 10 Highly regioselective reaction at C6-H Proceeds under mild conditions (at room temp, < 2 h) Formation of some aldehyde groups CH H H ph 10 CNa H H NaCl NaBr N H NaH Glucuronic acid unit N CH H H NaCl NaBr N CH 2 H H Glucose unit TEMP-mediated oxidation proceeds similarly to enzymatic reactions but more rapidly. H

3 TEMP-mediated oxidation of various celluloses Water (100 ml) TEMP ( g) NaBr (0.125 g) Cellulose fibers (1 g) Cellulose fibers / water slurry at room temp. and ph 10 NaCl / water 0.4M NaH addition to keep ph 10 Isolation & washing process TEMP-oxidized cellulose Analyses

4 Research projects of TEMP-oxidized celluloses in our lab TEMP oxidation of various celluloses, chitins & other polysaccharides Preparation & characterization of water-soluble TEMP-oxidized cellulose (cellouronic acid) prepared from regenerated celluloses TEMP oxidation of paper pulps to improve paper properties by introducing carboxyl & aldehyde groups Preparation & characterization of TEMP-oxidized cellulose nanofibers, supported by JSPS NED Nanotech Challenge Project for high gas-barrier packaging materials JSPS Bio-Nanofibril Project for fundamental research Applying METI National Project with companies, university labs & government for new bio-nanofibers (undecided)

5 Hierarchical structure of highly crystalline cellulose in plants Tree Fiber assembly Single fiber Bundle of microfibrils Cellulose microfibril Cellulose chain Fiber surface Wood Wood tissue Width : µm Length : 1 3 mm Width > 15 nm Width 3 4 nm Length > 5 µm Width 0.4 nm Length 500 nm Crystallinity %

6 Cellulose single nano-fibers from abundant biomass resources Cellulose single nano-fiber Cellulose molecules Downsizing processing Bottom-up processing Abundant wood biomass Width 3 4 nm Length > 5 µm Crystallinity %

7 ptical microphotographs of the original and TEMP-oxidized wood celluloses (never-dried) riginal wood cellulose TEMP-oxidized wood cellulose TEMP-mediated oxidation 50 µm Carboxylate content 0.05 mmol/g Carboxylate content 1.5 mmol/g Even though a significant amount of carboxylate groups is formed in TEMP-oxidized cellulose, no swelling of fibers in water is observed. Saito et al., Biomacromolecules, 2007

8 Metal ion content in TEMP-oxidized cotton celluloses after ion-exchange treatment TEMP-oxidized cellulose-cna TEMP-oxidized cellulose-cm Metal ion Metal ion content (mmol/g) Mg Al Ca Mn Co Ni Cu Sr Ag Cd Ba La Pb Metal ion treated Pb, Ca & Ag can form carboxylate salt almost 1:1 by molar ratio. Saito & Isogai, Carbohydrate Polymers, 2005

9 Biodegradation of TEMP-oxidized cellulose Disintegration TEMP-oxidized cellulose suspension in water Transparent dispersion TEM observation Domestic blender at 12,000 rpm < 4 min Ultrasonic homogenizer < 2 min Magnetic stirrer at 1,500 rpm ~ 12 days 50 nm

10 TEMP-mediated oxidation of various native celluloses -Effective surface modification of cellulose microfibril- Plants (tree) Electrostatic repulsion Cellulose microfibrils 4-5 nm 0.5 nm Cellulose nanofiber dispersion in water Anhydroglucose unit Disintegration in water µm Wood fiber TEMP-mediated oxidation N : -CH 2 H : Hemicellulose region TEMP : -C Na + : -CH 2 H TEMP-oxidized cellulose fibers suspended in water

11 100 nm Saito et al., Biomacromolecules, 2007

12 Wood cellulose fibers are the most suitable resources for preparing TEMP-oxidized cellulose nano-fibers Wood cellulose microfibrils Hemicellulose & disordered region N TEMP-mediated oxidation N H Glucose unit Glucuronate unit C Disintegration in water ζ-potential : 80mV

13 Structural model of TEMP-oxidized cellulose nanofiber riginal TEMP-oxidized wood cellulose microfibril nanofiber -CH 2 H Glucose unit 4 nm -C - Glucuronate unit 1.7 Carboxylate groups / nm 2

14 TEMP / NaBr / NaCl oxidation of polysaccharides at ph 10 Advantages points : Aqueous media at ph 10 Highly regioselective reaction at C6-H Proceeds under mild conditions (at room temp, < 2 h) Formation of some aldehyde groups CH H H ph 10 CNa H H NaCl NaBr N H NaH Glucuronic acid unit N CH H H NaCl NaBr N Depolymerization Discoloration etc. CH 2 H H Glucose unit TEMP-mediated oxidation proceeds similarly to enzymatic reactions but more rapidly. H

15 TEMP-mediated oxidation of cellulose using NaCl 2 at ph 3-7 Advantages : Aqueous media at ph 3-7 Highly regioselective reaction at C6-H No aldehydes are present in the oxidized products NaCl Proceeds under mild conditions (at C, 2-24 h) β-elimination and depolymerization is avoidable. N N Glucose unit CH 2 H H H NaCl CH H H thers TEMP-Peroxidase-H 2 2 TEMP-Laccase- 2 NaCl 2 Glucuronic acid unit CNa H H Saito et al., Biomacromolecules, 2009

16 Carboxylate content and DP of TEMP-oxidized celluloses ph xidation Carboxylate time (h) content (mmol/g) DP riginal wood cellulose ー ,260 xidized celluloses prepared by TEMP/NaCl/NaCl , , xidized celluloses prepared by TEMP / NaBr / NaCl DP values were determined by cuen viscosity method TEMP-oxidized celluloses prepared at ph 6.8 by TEMP / NaCl / NaCl 2 had higher DPs, although longer oxidation times were required. Saito et al., Biomacromolecules, 2009

17 100 nm

18 Size map of new TEMP-oxidized cellulose nano-fibers (TCN) prepared from native celluloses 1000 Bacterial cellulose CNT TCN 100 nm Length / diameter ratio CNT TCN Hydrolyzed cellulose whisker Mechanically fibrillated cellulose Diameter (nm) Rayon fibers Microcrystalline cellulose TCN covers new nano-fiber region at nm-level diameters in the map, which has not been prepared from other polymers or by other processes.

19 Differences in morphology and consumed energy between micro-fibrillate cellulose and TEMP-oxidized cellulose nano-fibers Micro-fibrillated cellulose TEMP-oxidized cellulose nanofibers 100 µm 100 nm Disintegration energy > 200 khw / kg More than 10 times cycles by highpressure homogenizer Disintegration energy < 2 khw / kg

20 ptical transparency of a TCN film 100 Transmittance (%) Wavelength (nm) The TCN films obtained are transparent and bendable. Fukuzumi et al., Biomacromolecules, 2008

21 Coefficient of thermal expansion of TCN film ppm / K Expansion (%) Temperature ( C) The extremely low CTE of TCN films is available for electronic and flexible display devices. The CTE of glass is ca. 8 ppm / K. Fukuzumi et al., Biomacromolecules, 2008

22 Changes in water contact angle on TCN films by 0.05% AKD treatment 120 Contact angle ( ) % AKD-treated TCN film riginal TCN film Time (s) The surface hydrophilicity of TCN films is controllable by simple soaking treatment in AKD dispersion and drying. Fukuzumi et al., Biomacromolecules, 2008

23 NED Nanotech Challenge Programs Stage I from 2007 to 2010 Project title NED: New Energy and Industrial Technology Development rganization of Japan, and is an affiliated organization of Ministry of Economy, Trade and Industry Development of environment compliant high-capability packaging components using cellulose single nano-fiber rganizations: Kao Corporation, Nippon Paper Industries, The University of Tokyo Project Leader: Akira Isogai (The University of Tokyo) utline: TEMP-oxidized cellulose single nanofibers (TCN) are new biobased nano-materials with various potential applications. During the development research of applying TCN to environmentallycompatible and high-performance packaging components, we work toward the creation of sustainable society.

24 Development of environment compliant high-performance packaging components using TEMP-oxidized cellulose single nano-fibers (NED project) Background General waste in Japan 5.2 Mt / y Electricity / machinery 0.18 Mt 3.4% Household 1.05 Mt, 20.2% thers 0.3 Mt, 5.8% Containers/ packaging 3.67 Mt, 70.6% thers 0.21 Mt 3% Household commodity 0.19 Mt, 3.9% Agriculture Forestry Fisheries 0.19 Mt 3.9% Transportation 0.33 Mt, 6.8% Industrial waste in Japan 4.9 Mt / y Production Processing waste 0.92 Mt 18.9% Building products 0.71 Mt 14.6% Electricity Machinery 1.2 Mt, 24.7% Containers packaging 1.14 Mt 23.5% TEMP N 100 nm Wood cellulose Incineration disposal: 53% (5.4 Mt/y) TEMP-oxidized cellulose nanofibers C 2 emission: 6.7 M t / year New environmentally compatible packaging materials are needed. Matching Goal Development of environmentally friendly packaging materials with high-bas barrier properties, from TEMP-oxidized cellulose nanofibers and bioplastics