Supporting Information Individually Dispersed Wood-Based Cellulose Nanocrystals Huibin Chang a, b, Jeffrey Luo a, b, Amir A. Bakhtiary Davijani a, An-Ting Chien a, Po-Hsiang Wang a, H. Clive Liu a, b a, b, *, and Satish Kumar a School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 b Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA, 30332 Corresponding author's email address: satish.kumar@mse.gatech.edu S-1
Supplemental Information Materials Cellulose nanocrystals with approximately 5 nm in diameter and 150-200 nm length were obtained from Process Development Center, University of Maine (freeze-dried powder, lot# 2012-FPL-CNC-48/051, 1.05 wt % sulfur) 1-2. SEM images of the CNCs used in this study are shown in Figure S1.The as-received CNCs are highly agglomerated micro-size sheets and individual CNC are visible at the edge of the sheet. Dimethyl formamide (DMF) obtained from BDH, Inc. was purified by distillation before use. Figure S1. SEM images of the as-received CNCs Preparation of CNC/DMF dispersion The moisture content of as-received CNCs is 3.8 wt % as determined by TGA (TA Instrument, Q500). The as-received CNCs was put in a glass bottle with loose lid and dried in oven at 105 C for various times to obtain lower moisture-containing CNCs. The moisture content of dried CNCs was then determined by TGA (Figure S2). Various CNCs were dispersed in DMF, DMF/water mixture, or in water using a sonication bath (Branson 3510R-MT, 100 W, 42 khz). S-2
Weight (%) 100.5 100.0 99.5 99.0 98.5 98.0 97.5 97.0 96.5 96.0 95.5 95.0 0 d c b a 0 10 20 30 40 50 Time (minute) Figure S2. TGA of various CNCs at 120 C (a) as received CNC; (b) and (c) as received CNCs vacuum dried at 105 C in vacuum oven for 6 and 12 hrs, respectively; (d) as received CNCs dried at 105 C in vacuum oven for 48 hrs. Characterization Cellulose nanocrystals (CNCs) were observed using scanning electron microscope (SEM, Zeiss Ultral60). For TEM, drops of dilute CNC dispersion were deposited on carbon-coated electron microscope grids and negatively stained with uranyl acetate (CF200-Cu, 200 Mesh, Electron Microscopy Sciences, Hatfield, PA). TEM images were obtained using a probe corrected scanning/transmission electron microscope JEL JEM-ARM200cF (JEL, Ltd, Tokyo, Japan) operated at 80kV. The dimension of CNCs was measured by ImageJ software. Dynamic light scattering (DLS) study was conducted using BI-200SM light scattering system (Brookhaven Instruments Co.), with the detector at 90 degrees, power at 11 mw, and a vertically polarized 532 nm laser. The solutions were kept at 25 C during DLS measurement, and the data collection duration was 2 min. Each solution was measured at least 5 times. The viscosity and refractive index of mixture of H 2 /DMF are based on literature data 3-4 using linear interpolation method and they are summarized in Table S1. The refractive index of CNCs used in this study is 1.47. Zeta potential of CNC/DMF (CNC containing 3.8 wt% moisture) solutions with different sonication time was measured by Zetasizer Nano ZS90 (Malvern Instruments) as shown in Table S-3
S2. Zeta potential was measured to fully characterize CNCs. However, its effect on dispersibility was not evaluated. The solution spectra were recorded by a Nicolet Magna-560 Fourier transform infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode. FTIR spectra were recorded in a spectral range of 4000-400 cm -1 with a resolution of 0.5 cm -1. Table S1. Viscosity and refractive index parameters used for DLS experiments. Volume Percent Water Viscosity Refractive Index in DMF (mpa s) 0 0.815 1.428 5 1.046 1.426 25 2.246 1.413 50 2.352 1.389 75 1.563 1.358 100 0.922 1.331 Table S2. Zeta potential of CNC/DMF solutions after different sonication times (CNCs 75 mg/100 ml DMF, CNC moisture content 3.8 wt%) Sonication time (hour) Zeta potential (mv) 1-14.5 ±1.6 2-16.1 ±1.4 4-15.2 ±1.6 8-16.0 ± 1.7 Figure S3. ptical images of CNCs with 3.8 wt% moisture in pure DMF (a), CNC with 0.6 wt% moisture in pure DMF (b) and in 50-50 volume percent H 2 /DMF mixture (c). S-4
(a) (b) (c) Figure S4. Representative TEM images of high CNC concentration (3g/100ml, 3.8 wt% moisture) in 5-95 volume percent H 2 /DMF mixture (a), pure water (b) and 25-75 volume percent H 2 /DMF mixture. For TEM study, all three samples were diluted by more than 100 times. (Note: Lower values of the calculated R h based on CNC dimensions obtained from TEM images are a result of the fact that TEM images are obtained on extremely dilute dispersions, and not at the concentrations used in light scattering experiments.) Table S3. Dimensions of CNC obtained from TEM dispersed in different solvents and the calculated hydrodynamic radius (R h ) 5-95 H 2 -DMF 25-75 H 2 -DMF Pure water Length (nm) 204 ± 57 153 ± 38 178 ± 27 Diameter (nm) 12.3 ± 2.5 6.3 ± 2.2 10.5 ± 2.2 Calculated R h 27-45 21-30 26-37 S-5
Absorbance 0.6 0.4 0 % H 2 5 % H 2 25 % H 2 50 % H 2 0.2 75 % H 2 100 % H 2 0.0 1800 1750 1700 1650 1600 1550 1500 Wavenumber (cm -1 ) Simulation Figure S5. ν(c) stretching region in FTIR spectra of CNC/DMF/H 2 dispersion Simulations are carried out in ChemBio3D 14 for energy minimization and simulation results are shown in supplemental videos. 4 CNC repeat units are initialized randomly in the DMF, H 2 or H 2 /DMF mixture. Using the molecular dynamics package, the molecules were heated to 300 K and kept at that temperature for 300 picoseconds. S-6
References S1. Lahiji, R. R.; Xu, X.; Reifenberger, R.; Raman, A.; Rudie, A.; Moon, R. J., Atomic Force Microscopy Characterization of Cellulose Nanocrystals. Langmuir 2010, 26 (6), 4480-4488. S2. Postek, M. T.; Vladár, A.; Dagata, J.; Farkas, N.; Ming, B.; Wagner, R.; Raman, A.; Moon, R. J.; Sabo, R.; Wegner, T. H., Development of the Metrology and Imaging of Cellulose Nanocrystals. Meas. Sci. Technol. 2011, 22 (2), 024005. S3. Bernal-García, J. M.; Guzmán-López, A.; Cabrales-Torres, A.; Estrada-Baltazar, A.; Iglesias-Silva, G. A., Densities and Viscosities of (N, N-Dimethylformamide+ Water) at Atmospheric Pressure from (283.15 to 353.15) K. Journal of Chemical & Engineering Data 2008, 53 (4), 1024-1027. S4. Wohlfarth, C., Refractive Index of the Mixture (1) Water;(2) N, N-Dimethylformamide. In Refractive indices of pure liquids and binary liquid mixtures (supplement to III/38), Springer: 2008, pp 580-581. S-7