Degrees of polymerization (DP) and DP distribution of cellouronic acids prepared from alkali-treated celluloses and ball-milled native celluloses by TEMPO-mediated oxidation

Isogai, Takuya; Yanagisawa, Masahiro; Isogai, Akira

doi:10.1007/s10570-008-9245-1

Cited by 79 publications

(51 citation statements)

References 24 publications

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“…3j). Further support comes from the literature (Teeaar et al 1987;Hulleman et al 1994;Stubičar et al 1998;Isogai et al 2009) wherein the peak position in completely amorphous cellulose is reported to be 20-21°and not 18°(as Segal et al 1959 reported). Although not clear why this is the case, the finding of the higher 2h value may possibly result from the Fig.…”

Section: Ball Milled Samplesmentioning

confidence: 77%

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

2010

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Two new methods based on FT-Raman spectroscopy, one simple, based on band intensity ratio, and the other using a partial least squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1,096 cm -1 bands. For calibration purposes, 80.5% crystalline and 120-min milled (0% crystalline) Whatman CC31 and six cellulose mixtures produced with crystallinities in the range 10.9-64% were used. When intensity ratios were plotted against crystallinities of the calibration set samples, the plot showed a linear correlation (coefficient of determination R 2 = 0.992). Average standard error calculated from replicate Raman acquisitions indicated that the cellulose Raman crystallinity model was reliable. Crystallinities of the cellulose mixtures samples were also calculated from X-ray diffractograms using the amorphous contribution subtraction (Segal) method and it was found that the Raman model was better. Additionally, using both Raman and X-ray techniques, sample crystallinities were determined from partially crystalline cellulose samples that were generated by grinding Whatman CC31 in a vibratory mill. The two techniques showed significant differences. In the second approach, successful Raman PLS regression models for crystallinity, covering the 0-80.5% range, were generated from the ten calibration set Raman spectra. Both univariateRaman and WAXS determined crystallinities were used as references. The calibration models had strong relationships between determined and predicted crystallinity values (R 2 = 0.998 and 0.984, for univariateRaman and WAXS referenced models, respectively). Compared to WAXS, univariate-Raman referenced model was found to be better (root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values of 6.1 and 7.9% vs. 1.8 and 3.3%, respectively). It was concluded that either of the two Raman methods could be used for cellulose I crystallinity determination in cellulose samples.

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Section: Ball Milled Samplesmentioning

confidence: 77%

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

2010

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“…Preparation of cellouronic acid (CUA) CUA was prepared from regenerated cellulose by the TEMPO/NaBr/NaClO system at pH 10 according to the reported method (Isogai and Kato 1998;Isogai et al 2009). Regenerated cellulose (1 g) was suspended in water (100 mL) at pH 10 containing TEMPO (0.025 g, 0.16 mmol) and NaBr (0.25 g, 2.4 mmol).…”

Section: Methodsmentioning

confidence: 99%

“…When 2,2,6,6-tetramethylpiperidinyl-1-oxyl radical (TEMPO)-mediated oxidation with NaBr and NaClO in water at pH 10 is applied to regenerated, mercerized or ball-milled native celluloses, watersoluble polyglucuronates (cellouronic acid Na salts, CUA) are obtained quantitatively (Isogai and Kato 1998;Isogai et al 2009). CUA has mostly homogeneous chemical structures consisting of (1 ?…”

Section: Introductionmentioning

confidence: 99%

Temperature and pH stability of cellouronic acid

Fujisawa

Isogai

2010

Cellulose

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Cellouronic acid (CUA), (1 ? 4)-b-D-polyglucuronate sodium salt, was prepared from regenerated cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation in water at pH 10. Changes in chemical structure and degree of polymerization (DP) of CUA by treatment in water under various pH and temperature conditions were studied to evaluate the stability of CUA. No depolymerization occurred on CUA in water at pH 1.0-7.0 and room temperature, while clear depolymerization took place at pH 10 and 13 by b-elimination. When heated in water at[50°C, CUA was depolymerized by hydrolysis at pH 1.0 and 4.8, and by both hydrolysis and b-elimination at pH 7.0. Kinetic studies showed that CUA depolymerization rate constant was roughly increased with increasing the pH or temperature. Especially, the depolymerization rate constant at pH 13 was approximately 128 and 55 times greater than those at pH 1.0 and 10, respectively, at 60°C. Activation energies of hydrolysis and b-elimination of CUA were approximately 100 and 20 kJ mol -1 , respectively.

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“…When the TEMPO/NaBr/NaClO oxidation at pH 9-11 or 4-acetamide-TEMPO/NaClO/NaClO 2 oxidation at pH 4.8-6.8 was applied to regenerated celluloses under proper conditions, water-soluble cellouronic acids were obtained in most cases by regioselective oxidation of C6 primary hydroxyls to carboxylate groups (Isogai and Kato 1998;Isogai et al 2009;Hirota et al 2009a). Because serious depolymerization of cellouronic acids caused by belimination or some active radicals formed as byproducts during TEMPO-mediated oxidation at pH 9-11 (Shibata and Isogai 2003) can be excluded under the oxidation conditions at pH 4.8-6.8, cellouronic acids with higher DPs are obtained quantitatively (Hirota et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

Water dispersion of cellulose II nanocrystals prepared by TEMPO-mediated oxidation of mercerized cellulose at pH 4.8

et al. 2009

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Mercerized wood cellulose was oxidized by 4-acetamide-TEMPO/NaClO/NaClO 2 system at 60°C and pH 4.8 for 1-5 days. Mostly individual nanocrystals 4-7 nm in width and 100-200 nm in length were obtained by ultrasonication of the oxidized product in water. The nanocrystals had the cellulose II structure, and carboxylate contents of 2.0-2.4 mmol/g, indicating that these carboxylate groups were selectively formed on the cellulose II crystallite surfaces in mercerized cellulose. Moreover, the original wood cellulose and mercerized cellulose were acid-hydrolyzed, and then subjected to the TEMPO-mediated oxidation under the same conditions at pH 4.8 to prepare reference samples. TEM images, light transmittance and rheological properties of water dispersions showed that the nanocrystals prepared from mercerized cellulose by the TEMPO oxidation and sonication in water had the highest dispersibility of individual nanocrystals with less amounts of bundles in water, resulting from the highest carboxylate contents.

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Degrees of polymerization (DP) and DP distribution of cellouronic acids prepared from alkali-treated celluloses and ball-milled native celluloses by TEMPO-mediated oxidation

Cited by 79 publications

References 24 publications

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Temperature and pH stability of cellouronic acid

Water dispersion of cellulose II nanocrystals prepared by TEMPO-mediated oxidation of mercerized cellulose at pH 4.8

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