Electronic Supplementary Material
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Cellulose Nanocrystals with CO2-Switchable Aggregation and
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Redispersion Properties
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Hai-Dong Wang, Philip G. Jessop, Jean Bouchard, Pascale Champagne*, Michael F.
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Cunningham*
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Corresponding author: M. F. Cunningham*
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Department of Chemical Engineering, Queen’s University, 19 Division Street, Kingston, Ontario
K7L 3N6, Canada
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e-mail: michael.cunningham@chee.queensu.ca; tel: 613-533-2782; fax 613-533-6637
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Co-Corresponding author: P. Champagne*
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Department of Civil Engineering, Queen’s University, 58 University Avenue, Kingston, Ontario
K7L 3N6, Canada
e-mail: champagne@civil.queensu.ca; tel: 613-533-3053; fax 613-533-2128
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1.82
1.62
CNC-APIm
Native CNC
1.42
1112 cm-1
1162 cm-1
Kubelka-Munk (-)
1.22
1.02
712 cm-1
1429 cm-1
-1
900 cm
0.82
0.62
0.42
0.22
0.02
-0.18
2000
1600
1200
800
-1
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Wavenumbers (cm )
Fig. S1 DRIFT-IR spectra of native CNC and CNC-APIm
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2
400
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Table S1 Degree of protonation of HPIm calculated by different protons at different conditions
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measured by 1H NMR spectroscopy (see Fig. 5 for the assignment of different protons in HPIm).
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HPIm concentration is fixed at 15 mg/ml
Degree of protonation at different conditionsa
Protons
Original
CO2 Sparging (5 min)
CO2 + N2 Sparging (5+30 min)
(%)
(%)
(%)
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7.0
77
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2
25
108
35
3
19
97
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Average
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94
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a
Data were recorded on a Bruker Avance 400 NMR spectrometer at 25oC using 90% H2O + 10%
  0
D2O as solvent. The degree of protonation was calculated as:
 100% , where  , 100 ,
100   0
and  0 denote a specific chemical shift and chemical shifts at 100% (1.0 M HCl) and 0% (1.0 M
NaOH) degree of protonation, respectively. To check reproducibility, all NMR measurements
were conducted at least in triplicate and differences for all repeated measurements were less than
5%. Only one set of data were used for the calculation in this table. The degree of protonation
value is not exact.
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Calculation of Surface Imidazole and Sulfate Densities
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The elemental analysis data (Table 1) show that: 1. the two CNC-APIm samples are consistent
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suggesting high reproducibility of the CNC-APIm preparation and purification procedures as
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described in this work and; 2. the S concentrations for native CNC and CNC-APIm are similar
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indicating that the sulfate groups are not significantly hydrolyzed after the CNC-APIm
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preparation and purification processes. According to the TEM images (Fig. 6), native CNC and
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CNC-APIm show similar dimensions with lengths ranging from around 100 nm to 300 nm and
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diameters of ca. 10 nm. Treating CNC as a nanorod with a square cross-section, we made the
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following assumptions before conducting an approximate calculation of the APIm and sulfate
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density on the CNC surface:
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1. Both CNC and CNC-APIm are nanorods with a square cross-section of 7.1 nm × 7.1 nm
(diagonal: 10 nm). The nanorods have non-reactive ends;
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2. Any cross-section of CNC and CNC-APIm, along the axial direction, is packed with
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cellulose Iβ unit cells in the same pattern. These cellulose unit cells, as determined by X-ray
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diffraction (Sugiyama et al. 1991), have cross-sectional dimensions of 0.61 nm × 0.54 nm in
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the directions parallel to the two sides of CNC square cross-section (Habibi et al. 2006);
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3. Anhydrous glucose units (AGUs) are evenly distributed on four sides of each cellulose unit
cell with the two ends having no AGU;
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4. The sulfate groups remain intact after the APIm coupling reaction;
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5. The CNC-APIm has the same density as native CNC which is around 1.6×10-21 g/nm3
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(Habibi et al. 2010; Majoinen et al. 2011).
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If we take 1 nm length (one unit volume) of CNC-APIm (side of cross-section is 7.1 nm as
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determined in the above assumption), then its volume and surface area are 50.4 nm3 and 28.4
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nm2, respectively. In the elemental analysis results (Table 1), the average of the two CNC-APIm
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measurements is used for the calculation. So the imidazole and sulfate molarities in one unit
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volume
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we have:
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Surface imidazole density: 1.53 units/nm2
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Surface sulfate density: 0.38 units/nm2.
are
(50.4×1.6×10-21)×3.75%/42=7.20×10-23
mol
and
(50.4×1.6×10-
)×0.72%/32=1.81×10-23 mol, respectively. Assuming that all of these groups are at the surface,
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In the same unit volume of CNC-APIm, there is (50.4×1.6×10-21)/162=4.98×10-22 mol of
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AGUs. The CNC-APIm surface cellulose units account for around 2×[(7.1/0.61+7.1/0.54)-
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2]/[7.1×7.1/(0.61×0.54)]=0.3 (30%) of the total mass. Then we have:
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Surface AGU to imidazole molar ratio: 4.98×10-22×0.3/(7.20×10-23)=2.08;
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Surface AGU to sulfate molar ratio: 4.98×10-22×0.3/(1.81×10-23)=8.25.
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