Concurrent Cellulose Hydrolysis and Esterification to Prepare Surface ...
Concurrent Cellulose Hydrolysis and Esterification to Prepare Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties
Stephen Spinella†,‡ Anthony Maiorana,† Qian Qian,† Nathan J. Dawson,§ Victoria Hepworth,† Scott A. McCallum, † Manoj Ganesh,‡ Kenneth D. Singer,§ and Richard A. Gross† †
Department of Chemistry and Biology, Rensselaer Polytechnic Institute (RPI), 4005B BioTechnology Bldg., 110 8th Street, Troy, N.Y. 12180, USA ‡
Department of Chemical and Bimolecular Engineering, NYU Polytechnic School of Engineering, Six Metrotech Center, Brooklyn, New York 11201, USA
§
Department of Physics, Case Western Reserve University, 2076 Adelbert Road, Cleveland, Ohio 44106, USA
*Corresponding Author Richard A. Gross; Email: [email protected]; Ph: 518-276-3734; Fax: 518-276-3405
Total number of pages: 13 Total number of Figures: 6 Total number of Tables: 11 Key Words: Cellulose nanocrystals, Fischer esterification, cellulose hydrolysis, carboxylic acid, nanocomposite, polyvinyl alcohol
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Contents: 1. List of Figures a) Figure SI: Quantitative solid-state Carbon NMR spectra for modified CNCs S5 b) Figure S2: Conductometric titration of modified CNCs with 0.1 M HCl S6 c) Figure S3: Thermogravimetric analysis of modified and unmodified CNCs under air with a heating rate of 20 °C/min. S7 d) Figure S4: Scanning Electron Microscopy (SEM) photomicrographs of: (a) Ramie fibers and cellulose co-products isolated from hydrolysis reactions (reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid) conducted with (b) malonic acid (c) citric acid and (d) malonic acids. Scale bar = 50, 100 and 500 nm S8 e) Figure S5: Wide angle X-Ray spectroscopy (WAXS) of ramie fibers and recovered cellulose particles. The later are co-products from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. S10 f) Figure S6: Wide angle X-Ray spectroscopy (WAXS) of citrate CNCs prepared from residual cellulose particles by reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% citric acid. S11 2. List of Tables a) Table S1: pKa of malonic, malic and citric acids S3 b) Table S2: Influence of the HCl concentration on the %-yield of citric acid CNCs, nonsolubilized cellulose (cellulose co-product) and water-soluble co-products. S3 S4 c) Table S3: Preparation of malonic and malate CNCs: effect of HCl concentrationa d) Table S4: Comparison of results reported herein to previous reports of one-pot acid catalyzed concurrent hydrolysis of amorphous cellulose segments and Fischer esterification reactions S4 e) Table S5: Determination of the crystallinity index of modified and non-modified cellulose by Wide Angle X-Ray Spectroscopy (WAXS) S5 f) Table S6: Amount of modification of CNCs S6 g) Table S7: Thermal stability of modified CNCs under nitrogen S7 h) Table S8: Thermal stability of modified CNCs under air S7 i) Table S9 Crystallinity index of residual cellulose particles recovered from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. S10 j) Table S10: Thermal stability of polyvinyl alcohol/CNC nanocomposites S11 k) Table S11: Thermal properties of polyvinyl alcohol/CNC nanocomposites S12 3. References S13
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Table S1: pKa of malonic, malic and citric acids Organic Acid pKa1 pKa2 pKa3 Malonic Acid1 2.83 5.69 Citric Acid2 3.15 4.77 6.40 Malic Acid2 3.5 5.2 1) Brown, H.C. et al., in Braude, E.A. and F.C. Nachod Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955 2) Dawson, R.M.C. et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959 Table S2: Influence of the HCl concentration on the %-yield of citric acid CNCs, non-solubilized cellulose (cellulose co-product) and water-soluble co-products.a HCl (Molarity) CNC Yield (%)b Yield (%) non- Yield (%) of water solubilized soluble co-productsd c cellulose 0.2 11.2 ± 4.0 75 ± 2 14 ± 3 0.1 19.6 ± 3.2 74 ± 3 5 ± 2.3 0.05 20.5 ± 5.2 72 ± 2 7 ± 3.7 0.025 18.75 ± 2.98 78 ± 3.4 3 ± 3.7 0.01 8.6 ± 1.52 85 ± 2 6 ± 2.2 0.005 7.5 ± 2.08 88 ± 1.0 4 ± 2.0 e 0 5.1 ± 3.2 93 ± 0.5 2 ± 1.2 a) Values reported are the mean from three independent experiments and the corresponding standard deviation. b) Determined gravimetrically from isolated modified CNCs after freeze drying. c) Determined gravimetrically from isolated non-solubilized material. d) Presumed to consist of glucose and corresponding oligomers. The %-yield is determined from the following equation: (100-[% yields of CNC + non-solubilized cellulose]).
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Table S3: Preparation of malonic and malate CNCs: effect of HCl concentrationa Organic Acid
HCl (M)
CNC Yield (%)b
Malonic Acid 0.2 9.0 Malonic Acid 0.1 20 ± 2 Malonic Acid 0.05 19 ± 3.1 Malonic Acid 0.025 19.8 ± 3.2 Malonic Acid 0.01 7.0 Malonic Acid 0.005 5.0 e Malonic Acid 0 4.8 ± 2 Malic Acid 0.2 13.5 ± 3.8 Malic Acid 0.1 18 ± 4.0 Malic Acid 0.05 20 ± 4.0 Malic Acid 0.025 17 ± 3 Malic Acid 0.01 9 Malic Acid 0.005 7 0 3.4 Malic Acide a-f) Table footnotes are identical to Table SI-2
Yield (%) non- Yield (%) of water solubilized soluble co-productsd c cellulose 72 19.0 76 ± 3.0 5 ± 3.8 73 ± 2.8 8±5 72 ± 2.0 8.5 ± 3.6 83.0 10.0 88.0 7.0 92 ± 2.0 3.0 ± 3 70 ± 5.0 17 ± 3.1 75 ± 4.0 5 ± 5.3 74 ± 5.2 6 ± 4.0 77 ± 2.0 6 ± 3.3 85 6.0 90 3.0 93 3.6
Table S4: Comparison of results reported herein to previous reports of one-pot acid catalyzed concurrent hydrolysis of amorphous cellulose segments and Fischer esterification reactions. Cellulose Organic Acid Average Degree of Yield (%) source (concentration wt-%) substitution Cotton1 Acetic acid (90%) 0.12 25 Cotton1 Butyric acid (90%) 0.11 20 Cotton2 Lactic acid (88%) 0.13 23 Formic acid (90%) Not reported Not reported Microcrystalline Cellulose3 Ramie Citric acid (80% ) 0.18 20.5 Ramie Malic acid (80%) 0.16 20.0 Ramie Malonic acid (80) 0.22 19.8
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Figure SI: Quantitative solid-state Carbon NMR spectra for modified CNCs Table S5: Determination of the crystallinity index of modified and non-modified cellulose by Wide Angle X-Ray Spectroscopy (WAXS) Crystallinity Index(%) Modified CNC a HCl-CNCs 74% Malate-CNCs 78% Malonate-CNCs 75% Citrate-CNCs 78% a reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid).
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Figure S2: Conductometric titration of modified CNCs with 0.1 M HCl
Table S6: Amount of modification of CNCs Modified CNC Acid amount (mmol COOH/kg cellulose)a TEMPO Oxidized CNCs4 1080 Citrate CNCs 1884 ± 124 Malate CNCs 1617 ± 170 Malonate CNCs 1108 ± 94 a) Determined by Conductometric Titration
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Figure S3. Thermogravimetric analysis of modified and unmodified CNCs under air with a heating rate of 20 °C/min.
Table S7: Thermal stability of modified CNCs under nitrogen T50%b(°C) Char (600°C)c Sample T10%a(°C) Malate CNCs 256 350 16 Citrate CNCS 288 345 20 Malonate CNCs 326 366 13 HCl CNCs 317 365 8 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative. c) Determined from residual weight at 600°C
Table S8: Thermal stability of modified CNCs under air Sample T10%a(°C) T50%b(°C) Malate CNCs 305 323 Citrate CNCS 267 324 Malonate CNCs 273 334 HCl CNCs 311 335 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative.
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Analysis of Pellets from Centrifugation Scanning electron microscopy (SEM) was performed on native ramie fibers and the residual cellulose co-product isolated after acid hydrolysis reactions with malonic-, malic- and citric acids. The SEM photomicrographs are shown in Figure SI-3.
Figure S4: Scanning Electron Microscopy (SEM) photomicrographs of: (a) Ramie fibers and cellulose co-products isolated from hydrolysis reactions (reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid) conducted with (b) malonic acid (c) citric acid and (d) malonic acids. Scale bar = 50, 100 and 500 m. Residual cellulose isolated as a co-product from concurrent cellulose hydrolysis and Fisher esterification reactions. The cellulose co-product is composed of micron sized particles. Average particle sizes of residual cellulose particles for reactions conducted with malic, citric and malonic acids are 50±10 µm (length) by 20±5 µm (width), 55±15 µm (length) by 30±10 µm (width) and 58±12 µm (length) by 17±5 µm (width), respectively. Neat ramie fibers (Figure SI-3) have
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lengths on the order of hundreds of microns and widths of approximately 100 nm. The morphologies of residual cellulose particles resemble microcrystalline cellulose (MCC).5 Indeed, MCC is also produced from native cellulose by acid hydrolysis.6 These micron sized particles do not form colloidal solutions. Consequently, they are easily separated from modified CNCs by centrifugation. TEMPO oxidation of cellulose has also been shown to result in micron sized particles.7 WAXS was performed on residual cellulose and the results are shown in Figure SI-3 and in Table SI-8. Crystallinity indexes for non-hydrolyzed residual cellulose particles from reactions using malic-, citric- and malonic acids are 73%, 72% and 69%, respectively. The crystallinity of neat ramie fibers is 60%. Based on SEM and WAXS analysis, residual cellulose is comprised of crystalline particles that are similar to MCC. Furthermore, FTIR experiments showed that residual cellulose particles are not functionalized (data not shown herein). It is well known that CNCs can be isolated from MCC using controlled acid hydrolysis.8
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Figure S5: Wide angle X-Ray spectroscopy (WAXS) of ramie fibers and recovered cellulose particles. The later are co-products from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid.
Table S9: Crystallinity index of residual cellulose particles recovered from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. Modified CNC Crystallinity Index(%) Malate-CNCs 73% Malonate-CNCs 72% Citrate-CNCs 69% Ramie Fibers 60
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Figure S6: Wide angle X-Ray spectroscopy (WAXS) of citrate CNCs prepared from residual cellulose particles by reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% citric acid. Table S10: Thermal stability of polyvinyl alcohol/CNC nanocomposites Sample T10%a(°C) T50%b(°C) Polyvinyl Alcohol 288 346 PVOH +1% HCl-CNCs 289 353 PVOH +1% Malonate-CNCs 283 345 PVOH +1% Malate-CNCs 299 360 PVOH +1% Citrate-CNCs 306 385 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative.
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Figure S11: Thermal properties of polyvinyl alcohol/CNC nanocompositesa Sample
Tm(°C)
∆H1 (J/g)
χ(%)b
Polyvinyl Alcohol (PVOH) 224.5 51.2 34 PVOH + 1% HCl CNCs 225.0 46.0 30 PVOH + 1% Malonate CNCs 227.6 51.9 35 PVOH + 1% Malate CNCs 229.0 68.1 45 PVOH + 1% Citrate CNCs 227.5 72.5 48 a) Determination by second scan DSC thermograms recorded under N2 flow with 10 °C/min heating rate from 0 to 250 °C. b) χ = (∆Hm)/∆H°m where ∆H°m = 150 J/g.9
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References: (1) (2)
(3)
(4) (5)
(6) (7)
(8)
(9)
Braun, B.; Dorgan, J. R. Ecobionanocomposites Based on Polylactide and Cellulosic Nanowhiskers: Synthesis and Propertie Biomacromolecules 2009, 10, 334–341. Spinella, S.; Lo Re, G.; Liu, B.; Dorgan, J.; Habibi, Y.; Leclère, P.; Raquez, J.-M.; Dubois, P.; Gross, R.A. Polylactide/Cellulose Nanocrystal Nanocomposites: Efficient Routes for Nanofiber Modification and Effects of Nanofiber Chemistry on PLA Reinforcement Polymer, 2015, 65, 9–17. Yu, H. Y.; Qin, Z. Y.; Sun, B.; Yan, C. F.; Yao, J. M. One-Pot Green Fabrication and Antibacterial Activity of Thermally Stable Corn-Like CNC/Ag Nanocomposites J. Nanoparticle Res. 2014, 16, 1–12. Way, A. E.; Hsu, L.; Shanmuganathan, K.; Weder, C.; Rowan, S. J. PH-responsive Cellulose Nanocrystal Gels and Nanocomposite ACS Macro Lett. 2012, 1, 1001–1006. Thoorens, G.; Krier, F.; Leclercq, B.; Carlin, B.; Evrard, B. Microcrystalline Cellulose, a Direct Compression Binder in a Quality by Design Environment-A Review. Int. J. Pharm. 2014, 473, 64–72. Nada, A.-A. M. A.; El-Kady, M. Y.; Abd El Sayed, E. S.; Amine, F. Preparation and Characterization of Anhydrothrombin. BioResources 2009, 4, 1359–1371. Peyre, J.; Pääkkönen, T.; Reza, M.; Kontturi, E. Simultaneous Preparation of Cellulose Nanocrystals and Micron-Sized Porous Colloidal Particles of Cellulose by TEMPOMediated Pxidation Green Chem. 2015, 17, 808–811. Çetin, N. S.; Tingaut, P.; Özmen, N.; Henry, N.; Harper, D.; Dadmun, M.; Sèbe, G. Acetylation of Cellulose Nanowhiskers with Vinyl Acetate Under Moderate Conditions Macromol. Biosci. 2009, 9, 997–1003. Ricciardi, R.; Auriemma, F.; Gaillet, C.; De Rosa, C.; Lauprêtre, F. Investigation of the Crystallinity of Freeze/Thaw Poly(Vinyl Alcohol) Hydrogels by Different Techniques Macromolecules 2004, 37, 9510–9516.
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Stephen Spinella†,‡ Anthony Maiorana,† Qian Qian,† Nathan J. Dawson,§ Victoria Hepworth,† Scott A. McCallum, † Manoj Ganesh,‡ Kenneth D. Singer,§ and Richard A. Gross† †
Department of Chemistry and Biology, Rensselaer Polytechnic Institute (RPI), 4005B BioTechnology Bldg., 110 8th Street, Troy, N.Y. 12180, USA ‡
Department of Chemical and Bimolecular Engineering, NYU Polytechnic School of Engineering, Six Metrotech Center, Brooklyn, New York 11201, USA
§
Department of Physics, Case Western Reserve University, 2076 Adelbert Road, Cleveland, Ohio 44106, USA
*Corresponding Author Richard A. Gross; Email: [email protected]; Ph: 518-276-3734; Fax: 518-276-3405
Total number of pages: 13 Total number of Figures: 6 Total number of Tables: 11 Key Words: Cellulose nanocrystals, Fischer esterification, cellulose hydrolysis, carboxylic acid, nanocomposite, polyvinyl alcohol
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Contents: 1. List of Figures a) Figure SI: Quantitative solid-state Carbon NMR spectra for modified CNCs S5 b) Figure S2: Conductometric titration of modified CNCs with 0.1 M HCl S6 c) Figure S3: Thermogravimetric analysis of modified and unmodified CNCs under air with a heating rate of 20 °C/min. S7 d) Figure S4: Scanning Electron Microscopy (SEM) photomicrographs of: (a) Ramie fibers and cellulose co-products isolated from hydrolysis reactions (reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid) conducted with (b) malonic acid (c) citric acid and (d) malonic acids. Scale bar = 50, 100 and 500 nm S8 e) Figure S5: Wide angle X-Ray spectroscopy (WAXS) of ramie fibers and recovered cellulose particles. The later are co-products from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. S10 f) Figure S6: Wide angle X-Ray spectroscopy (WAXS) of citrate CNCs prepared from residual cellulose particles by reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% citric acid. S11 2. List of Tables a) Table S1: pKa of malonic, malic and citric acids S3 b) Table S2: Influence of the HCl concentration on the %-yield of citric acid CNCs, nonsolubilized cellulose (cellulose co-product) and water-soluble co-products. S3 S4 c) Table S3: Preparation of malonic and malate CNCs: effect of HCl concentrationa d) Table S4: Comparison of results reported herein to previous reports of one-pot acid catalyzed concurrent hydrolysis of amorphous cellulose segments and Fischer esterification reactions S4 e) Table S5: Determination of the crystallinity index of modified and non-modified cellulose by Wide Angle X-Ray Spectroscopy (WAXS) S5 f) Table S6: Amount of modification of CNCs S6 g) Table S7: Thermal stability of modified CNCs under nitrogen S7 h) Table S8: Thermal stability of modified CNCs under air S7 i) Table S9 Crystallinity index of residual cellulose particles recovered from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. S10 j) Table S10: Thermal stability of polyvinyl alcohol/CNC nanocomposites S11 k) Table S11: Thermal properties of polyvinyl alcohol/CNC nanocomposites S12 3. References S13
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Table S1: pKa of malonic, malic and citric acids Organic Acid pKa1 pKa2 pKa3 Malonic Acid1 2.83 5.69 Citric Acid2 3.15 4.77 6.40 Malic Acid2 3.5 5.2 1) Brown, H.C. et al., in Braude, E.A. and F.C. Nachod Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955 2) Dawson, R.M.C. et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959 Table S2: Influence of the HCl concentration on the %-yield of citric acid CNCs, non-solubilized cellulose (cellulose co-product) and water-soluble co-products.a HCl (Molarity) CNC Yield (%)b Yield (%) non- Yield (%) of water solubilized soluble co-productsd c cellulose 0.2 11.2 ± 4.0 75 ± 2 14 ± 3 0.1 19.6 ± 3.2 74 ± 3 5 ± 2.3 0.05 20.5 ± 5.2 72 ± 2 7 ± 3.7 0.025 18.75 ± 2.98 78 ± 3.4 3 ± 3.7 0.01 8.6 ± 1.52 85 ± 2 6 ± 2.2 0.005 7.5 ± 2.08 88 ± 1.0 4 ± 2.0 e 0 5.1 ± 3.2 93 ± 0.5 2 ± 1.2 a) Values reported are the mean from three independent experiments and the corresponding standard deviation. b) Determined gravimetrically from isolated modified CNCs after freeze drying. c) Determined gravimetrically from isolated non-solubilized material. d) Presumed to consist of glucose and corresponding oligomers. The %-yield is determined from the following equation: (100-[% yields of CNC + non-solubilized cellulose]).
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Table S3: Preparation of malonic and malate CNCs: effect of HCl concentrationa Organic Acid
HCl (M)
CNC Yield (%)b
Malonic Acid 0.2 9.0 Malonic Acid 0.1 20 ± 2 Malonic Acid 0.05 19 ± 3.1 Malonic Acid 0.025 19.8 ± 3.2 Malonic Acid 0.01 7.0 Malonic Acid 0.005 5.0 e Malonic Acid 0 4.8 ± 2 Malic Acid 0.2 13.5 ± 3.8 Malic Acid 0.1 18 ± 4.0 Malic Acid 0.05 20 ± 4.0 Malic Acid 0.025 17 ± 3 Malic Acid 0.01 9 Malic Acid 0.005 7 0 3.4 Malic Acide a-f) Table footnotes are identical to Table SI-2
Yield (%) non- Yield (%) of water solubilized soluble co-productsd c cellulose 72 19.0 76 ± 3.0 5 ± 3.8 73 ± 2.8 8±5 72 ± 2.0 8.5 ± 3.6 83.0 10.0 88.0 7.0 92 ± 2.0 3.0 ± 3 70 ± 5.0 17 ± 3.1 75 ± 4.0 5 ± 5.3 74 ± 5.2 6 ± 4.0 77 ± 2.0 6 ± 3.3 85 6.0 90 3.0 93 3.6
Table S4: Comparison of results reported herein to previous reports of one-pot acid catalyzed concurrent hydrolysis of amorphous cellulose segments and Fischer esterification reactions. Cellulose Organic Acid Average Degree of Yield (%) source (concentration wt-%) substitution Cotton1 Acetic acid (90%) 0.12 25 Cotton1 Butyric acid (90%) 0.11 20 Cotton2 Lactic acid (88%) 0.13 23 Formic acid (90%) Not reported Not reported Microcrystalline Cellulose3 Ramie Citric acid (80% ) 0.18 20.5 Ramie Malic acid (80%) 0.16 20.0 Ramie Malonic acid (80) 0.22 19.8
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Figure SI: Quantitative solid-state Carbon NMR spectra for modified CNCs Table S5: Determination of the crystallinity index of modified and non-modified cellulose by Wide Angle X-Ray Spectroscopy (WAXS) Crystallinity Index(%) Modified CNC a HCl-CNCs 74% Malate-CNCs 78% Malonate-CNCs 75% Citrate-CNCs 78% a reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid).
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Figure S2: Conductometric titration of modified CNCs with 0.1 M HCl
Table S6: Amount of modification of CNCs Modified CNC Acid amount (mmol COOH/kg cellulose)a TEMPO Oxidized CNCs4 1080 Citrate CNCs 1884 ± 124 Malate CNCs 1617 ± 170 Malonate CNCs 1108 ± 94 a) Determined by Conductometric Titration
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Figure S3. Thermogravimetric analysis of modified and unmodified CNCs under air with a heating rate of 20 °C/min.
Table S7: Thermal stability of modified CNCs under nitrogen T50%b(°C) Char (600°C)c Sample T10%a(°C) Malate CNCs 256 350 16 Citrate CNCS 288 345 20 Malonate CNCs 326 366 13 HCl CNCs 317 365 8 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative. c) Determined from residual weight at 600°C
Table S8: Thermal stability of modified CNCs under air Sample T10%a(°C) T50%b(°C) Malate CNCs 305 323 Citrate CNCS 267 324 Malonate CNCs 273 334 HCl CNCs 311 335 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative.
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Analysis of Pellets from Centrifugation Scanning electron microscopy (SEM) was performed on native ramie fibers and the residual cellulose co-product isolated after acid hydrolysis reactions with malonic-, malic- and citric acids. The SEM photomicrographs are shown in Figure SI-3.
Figure S4: Scanning Electron Microscopy (SEM) photomicrographs of: (a) Ramie fibers and cellulose co-products isolated from hydrolysis reactions (reaction conditions: 3 hours, 140°C, 0.05 M HCl, 80% organic acid) conducted with (b) malonic acid (c) citric acid and (d) malonic acids. Scale bar = 50, 100 and 500 m. Residual cellulose isolated as a co-product from concurrent cellulose hydrolysis and Fisher esterification reactions. The cellulose co-product is composed of micron sized particles. Average particle sizes of residual cellulose particles for reactions conducted with malic, citric and malonic acids are 50±10 µm (length) by 20±5 µm (width), 55±15 µm (length) by 30±10 µm (width) and 58±12 µm (length) by 17±5 µm (width), respectively. Neat ramie fibers (Figure SI-3) have
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lengths on the order of hundreds of microns and widths of approximately 100 nm. The morphologies of residual cellulose particles resemble microcrystalline cellulose (MCC).5 Indeed, MCC is also produced from native cellulose by acid hydrolysis.6 These micron sized particles do not form colloidal solutions. Consequently, they are easily separated from modified CNCs by centrifugation. TEMPO oxidation of cellulose has also been shown to result in micron sized particles.7 WAXS was performed on residual cellulose and the results are shown in Figure SI-3 and in Table SI-8. Crystallinity indexes for non-hydrolyzed residual cellulose particles from reactions using malic-, citric- and malonic acids are 73%, 72% and 69%, respectively. The crystallinity of neat ramie fibers is 60%. Based on SEM and WAXS analysis, residual cellulose is comprised of crystalline particles that are similar to MCC. Furthermore, FTIR experiments showed that residual cellulose particles are not functionalized (data not shown herein). It is well known that CNCs can be isolated from MCC using controlled acid hydrolysis.8
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Figure S5: Wide angle X-Ray spectroscopy (WAXS) of ramie fibers and recovered cellulose particles. The later are co-products from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid.
Table S9: Crystallinity index of residual cellulose particles recovered from reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% organic acid. Modified CNC Crystallinity Index(%) Malate-CNCs 73% Malonate-CNCs 72% Citrate-CNCs 69% Ramie Fibers 60
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Figure S6: Wide angle X-Ray spectroscopy (WAXS) of citrate CNCs prepared from residual cellulose particles by reactions conducted for 3 hours at 140°C with 0.05 M HCl and 80% citric acid. Table S10: Thermal stability of polyvinyl alcohol/CNC nanocomposites Sample T10%a(°C) T50%b(°C) Polyvinyl Alcohol 288 346 PVOH +1% HCl-CNCs 289 353 PVOH +1% Malonate-CNCs 283 345 PVOH +1% Malate-CNCs 299 360 PVOH +1% Citrate-CNCs 306 385 a) Determined by TGA under N2 at a heating rate of 20°C/min b) Determined from the peak of the derivative.
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Figure S11: Thermal properties of polyvinyl alcohol/CNC nanocompositesa Sample
Tm(°C)
∆H1 (J/g)
χ(%)b
Polyvinyl Alcohol (PVOH) 224.5 51.2 34 PVOH + 1% HCl CNCs 225.0 46.0 30 PVOH + 1% Malonate CNCs 227.6 51.9 35 PVOH + 1% Malate CNCs 229.0 68.1 45 PVOH + 1% Citrate CNCs 227.5 72.5 48 a) Determination by second scan DSC thermograms recorded under N2 flow with 10 °C/min heating rate from 0 to 250 °C. b) χ = (∆Hm)/∆H°m where ∆H°m = 150 J/g.9
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References: (1) (2)
(3)
(4) (5)
(6) (7)
(8)
(9)
Braun, B.; Dorgan, J. R. Ecobionanocomposites Based on Polylactide and Cellulosic Nanowhiskers: Synthesis and Propertie Biomacromolecules 2009, 10, 334–341. Spinella, S.; Lo Re, G.; Liu, B.; Dorgan, J.; Habibi, Y.; Leclère, P.; Raquez, J.-M.; Dubois, P.; Gross, R.A. Polylactide/Cellulose Nanocrystal Nanocomposites: Efficient Routes for Nanofiber Modification and Effects of Nanofiber Chemistry on PLA Reinforcement Polymer, 2015, 65, 9–17. Yu, H. Y.; Qin, Z. Y.; Sun, B.; Yan, C. F.; Yao, J. M. One-Pot Green Fabrication and Antibacterial Activity of Thermally Stable Corn-Like CNC/Ag Nanocomposites J. Nanoparticle Res. 2014, 16, 1–12. Way, A. E.; Hsu, L.; Shanmuganathan, K.; Weder, C.; Rowan, S. J. PH-responsive Cellulose Nanocrystal Gels and Nanocomposite ACS Macro Lett. 2012, 1, 1001–1006. Thoorens, G.; Krier, F.; Leclercq, B.; Carlin, B.; Evrard, B. Microcrystalline Cellulose, a Direct Compression Binder in a Quality by Design Environment-A Review. Int. J. Pharm. 2014, 473, 64–72. Nada, A.-A. M. A.; El-Kady, M. Y.; Abd El Sayed, E. S.; Amine, F. Preparation and Characterization of Anhydrothrombin. BioResources 2009, 4, 1359–1371. Peyre, J.; Pääkkönen, T.; Reza, M.; Kontturi, E. Simultaneous Preparation of Cellulose Nanocrystals and Micron-Sized Porous Colloidal Particles of Cellulose by TEMPOMediated Pxidation Green Chem. 2015, 17, 808–811. Çetin, N. S.; Tingaut, P.; Özmen, N.; Henry, N.; Harper, D.; Dadmun, M.; Sèbe, G. Acetylation of Cellulose Nanowhiskers with Vinyl Acetate Under Moderate Conditions Macromol. Biosci. 2009, 9, 997–1003. Ricciardi, R.; Auriemma, F.; Gaillet, C.; De Rosa, C.; Lauprêtre, F. Investigation of the Crystallinity of Freeze/Thaw Poly(Vinyl Alcohol) Hydrogels by Different Techniques Macromolecules 2004, 37, 9510–9516.
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