1. Regular Linking of Cellulose nanocrystals via Click Chemistry: Synthesis and formation of Cellulose Nanoplatelet Gels

2. TEMPO-mediated Oxidation of Cellulose Nanocrystals (CNCs) TEMPO –mediated oxidation selectively oxidizes the primary hydroxyl groups while leaving unaffected the secondary hydroxyl groups O O O O O O O OH OH OH OH OH OH OH OH OH OH HOOC HOOC HOOC HOOC O O O O O O O OH OH OH OH OH OH OH OH OH OH NaOOC NaOOC NaOOC NaOOC (n-2)/2 2,2,6,6-tetramethyl-1-piperidinyloxy-radical ( TEMPO) NaBr NaOCl pH 10 R.T. Montanari et al. Macromolecules, 2005, 38, 1665-1671

3. Fourier Transform Infrared Spectroscopy (FTIR) C=O band CNCs TEMPO-oxidized CNCs 1730 cm -1 New signal at 1730 cm -1 indicates successful oxidation reaction

4. Degree of Oxidation (DO) DO was determined by using acid-base titration and FTIR Excellent correlation was found between these two methods Results are in good agreement with the recent literature (Montanari et al., Macromolecules, 2005, 38, 1665-1671, Saito et al., Biomacromolecules, 2006, 7, 1687-1691)

5. Strong Acid – Weak Acid Titration 50 mg of dry TEMPO-oxidized material was suspended in 15 ml of 0.01 M HCl. After 10 min of stirring the suspension was titrated with 0.01M NaOH. 162 x C x (V2-V1) w-36 x C x (V2-V1) = 0.19 DO= Where, C= NaOH conc. V1, V2= amount of NaOH (L) W= weight of the O.D. sample (g) Value 36 is the difference between the molecular weight of an AGU and that of the sodium salt of a glucuronic acid Weak acid region Da Silva Perez et al., Biomacromolecules, 2003, 4, 1417-1425

6. FT-IR DO= I 1730 I 1050 ≈ 0.20 COOH (1730) Cellulose backbone (1050) Habibi, Y., Chanzy, H., and Vignon, M. R. Cellulose, 2006, 13(6), 679-687.

7. In general, 1,3-dipolar cycloaddition reactions have long been popular in the generation of carbohydrate mimetics in the homogeneous reaction environment. 1 The reaction has gained increasing attention after discovering that the 1,3- dipolar cycloaddition between azides and terminal alkynes can be catalysed by Cu(I) salts. 2,3 Several authors have described the use of this novel click-chemistry concept for the generation of carbohydrate mimetics and derivatives. 4,5,6 Click Chemistry 1. Gallos, J. K. and Koumbis, A. E. Curr. Org. Chem., 2003, 7(5), 397–426. 2. Tornøe, C. W.; Christensen, C.; and Meldal, M. J. Org. Chem., 2002, 67(9), 3057–3064. 3. Rostovtsev, V. V.; Green, L. G.; Fokin V. V.; and Sharpless, K. B. Angew.Chem., Int. Ed., 2002, 41(14), 2596–2599. 4. Huisgen, R. Pure Appl. Chem., 1989, 61(4), 613−628. 5. Kolb, H. C; Finn, M. G; and Sharpless, K. B. Angew. Chem., Int. Ed., 2001, 40(11), 2004−2021. 6. Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.; Scheel, A.; Voit, B.; Pyun, J.; Fréchet, J. M. J.; Sharpless, K. B.; and Fokin, V. V. Angew. Chem., Int. Ed., 2004, 43(30), 3928 −3932.

8. Huisgen Cycloaddition Cellulose nanoplatelet gels (Click chemistry) Grafting click precursors onto TEMPO-oxidized CNCs Huisgen reaction (1,3-dipolar cycloaddition) The Huisgen Cycloaddition is the reaction of a dipolarophile with a 1,3-dipolar compound that leads to 5-membered (hetero)cycles.

9. The Creation of the Azido Functionality on the Nano Crystals N 3 (2120 cm -1 ) C=O (1730 cm -1 )

10. The Creation of the Alkyne Precursor on the Crystals

11. The Formation of CNC-Based Click-Gels N 3 disappeared

12. Click Reaction Precursors in H 2 O Gel formation: Elemental analysis: Sample% C% H% N% O a Tempo-ox. CNC41.755.760.0852.41 CNC43.556.110.0450.30 CNC-AZ42.875.201.9050.03 CNC-PR43.205.290.7950.72 CNC-Click43.286.031.5149.18 a O = 100 % - C (%) – H (%) – N (%) CuSO 4 Ascorbic acid vigorous stirring (1 min) The grafting densities of CNC-PR and CNC-AZ were calculated by using the DO value of 0.20 for Tempo-oxidized CNCs and the elemental composition of CNC-PR and CNC-AZ ; grafting densities of CNC-PR and CNC-AZ were found to be ~50% and ~35%, respectively

13. Transmission Electron Microscopy Individual CNC TEM images of TEMPO-oxidized cellulose nanocrystals (a) and cellulose nano-platelet gel (b). Scale bar 500 nm ab The average dimensions of the crystals were found to be approximately 10-20 nm width and 100-200 nm long.

14. Thermogravimetric Analysis CNC-Click CNC-Click has different thermal properties than its precursors

15. Benzoylation of Cellulose; Allowing the Visualization of Mol. Weight Distribution Cell-OH + Benzoyl-Cl Cell-Bz Reaction is carried out in Ionic Liquid UV – active benzoyl group Benzoylated cellulose is completely soluble in THF (compatible with GPC)

16. Gel Permeation Chromatography CNC-Click Solid line (CNC-Click); Dotted line (CNC-PR); Dashed line (CNC-AZ) CNC-click showed significantly higher molecular weight (cross-linking) Than its precursors (CNC-AZ and CNC-PR) SampleM n (1 x10 3 gmol -1 ) M W (1 x10 3 gmol -1 ) M p (1 x10 3 gmol -1 ) PD CNC2869514.1 CNC-PR2172533.5 CNC-AZ1553353.4 CNC-Click273356312.6

17. Summary  The primary hydroxyl groups in cellulose nanocrystals were first selectively oxidized to carboxylic acids which were further used as reactive sites for the amidation reactions to provide the precursors necessary for the Click chemistry reaction.  Click-chemistry has been utilized for the preparation of new gel-like cellulose nanomaterials.  Benzoylation of CNCs allows complete dissolution of material into THF and makes GPC analysis possible