Studies in chemically modified celluloses. III. Estimation of free carboxylic acid groups in oxycellulose

Nabar, G. M.; Shenai, V. A.

doi:10.1002/app.1970.070140509

Cited by 14 publications

(4 citation statements)

References 14 publications

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“…The NaClO 2 oxidation selectively converts the C6-aldehydes, which are formed as intermediates during the TEMPO-mediated oxidation, to C6-carboxyls (Figure S1 in Supporting Information). The NaBH 4 treatment can convert the C6-aldehydes and C2/C3 ketones to hydroxyls. − …”

Section: Resultsmentioning

confidence: 99%

“…An aliquot of the TOC (∼0.5 g) was further treated with 1% NaClO 2 (50 mL) at pH 4.8 and room temperature for 2 days to oxidize C6-aldehydes present in the oxidized cellulose to carboxyls and washed thoroughly with water. Another aliquot of the TOC (∼0.5 g) was treated with 0.5 g NaBH 4 in water (95 mL) for 2 days at room temperature and pH ∼9, which was adjusted by adding a 0.5 M NaHCO 3 solution to reduce C6-aldehydes and C2/C3 ketones to alcoholic hydroxyls, − and then washed thoroughly with water. The microcrystalline cellulose was oxidized by the TEMPO/NaBr/NaClO system at pH 10 and room temperature with NaClO of 10 mmol per gram of the cellulose.…”

Section: Methodsmentioning

confidence: 99%

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Relationship between Length and Degree of Polymerization of TEMPO-Oxidized Cellulose Nanofibrils

et al. 2012

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The influence of 2,2,6,6-tetrametylpiperidine-1-oxyl (TEMPO)-mediated oxidation of wood cellulose and the mechanical disintegration of oxidized cellulose in water on degree of polymerization determined by viscosity measurement (DP(v)) and the apparent length of the TEMPO-oxidized cellulose nanofibrils (TOCNs) was investigated. DP(v) values decreased from 1270 to 500-600 with increasing addition of NaClO in the TEMPO-mediated oxidation stage. The DP(v) values were further decreased by mechanical fibrillation in water. There is a linear relationship between the average fibril length and DP(v); the lengths of TOCNs can be approximated from DP(v) using 0.5 M copper ethylenediamine as a solvent of both the cellulose and oxidized celluloses in TOCNs. Based on the cellulose fibril models and TEMPO oxidation mechanism, the depolymerization behavior of TOCNs is tentatively explained in terms of distribution of disordered regions in wood cellulose fibrils and formation of C6-aldehydes in cellulose fibrils during TEMPO-mediated oxidation.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Relationship between Length and Degree of Polymerization of TEMPO-Oxidized Cellulose Nanofibrils

et al. 2012

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“…The product was centrifuged and immersed in 1M cold CH 3 COOH for 1 h. It was then centrifuged and washed with water. The reduced oxidized cellulose products were freezedried (Nabar and Shenai 1970;Shennai and Sudan 1972).…”

Section: Post-reduction Treatment Of Oxidized Cellulosementioning

confidence: 99%

Recoverable acrylamide-vinylamine copolymer immobilized TEMPO mediated oxidation of cellulose with good catalytic performance and low cellulose degradation

et al. 2021

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In this work, a recoverable acrylamide-vinylamine copolymer immobilized TEMPO (P(AM-co-VAm)-T) catalyst for selective oxidation of cellulose with good catalytic performance and low cellulose degradation was developed. Firstly, the acrylamide-vinylamine copolymer (P(AM-co-VAm)) was prepared by Hofmann degradation of polyacrylamide (PAM). Then, the condensation reduction reaction between amine groups of P(AM-co-VAm) and carbonyl groups of 4-oxo-TEMPO yielded P(AM-co-VAm)-T. P(AM-co-VAm)-T was used as a catalyst for selective oxidation of C6 primary hydroxyl groups of cellulose to carboxyl groups. The carboxyl content of obtained oxidized cellulose was up to 1.114 mmol/g, which was equivalent to 76% of the free TEMPO level. This macromolecular catalyst was easily recycled and the recycling performance was excellent. Interestingly, it was found that P(AM-co-VAm)-T could effectively reduce the degradation of oxidized cellulose. The corresponding degradation degree was 21%-27%, which was much lower than the degradation degree of free TEMPO (61%-66%) and other macromolecular TEMPO catalysts, such as polyacrylic acid immobilized-TEMPO (41%-53%) and polyamidoamine supported TEMPO (28%-44%). P(AM-co-VAm)-T with positive charge and suitable size could effectively inhibit the formation of C6 aldehydes and C2/C3 ketones, which was the main reason that it could signi cantly inhibit cellulose degradation.

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“…Oxidized cellulose, as a bio-based material widely used in high-tech elds, can be prepared by selective catalytic oxidation of primary hydroxyl groups in cellulose to carboxyl groups (Isogai et al 2011;Coseri et al 2012;Culica M E et al 2021;Nabar et al 1970). A variety of catalysts for selective catalytic oxidation of cellulose have been developed.…”

Section: Introductionmentioning

confidence: 99%

Recoverable Water-soluble Polyethylene Glycol-immobilized N-hydroxyphthalimide Mediated Oxidation of Cellulose in the Presence of NaBr and NaClO

Wang

Sun

et al. 2021

Preprint

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As a highly efficient nitroxide radical catalyst for selective catalytic oxidation of cellulose, N-hydroxyphthalimide (NHPI) has attracted much attention because of its low price and light cellulose degradation. However, NHPI is insoluble in water and is difficult to recycle because of its small molecular weight. To address the above issues, the water-soluble polyethylene glycol (PEG)-immobilized NHPI catalyst (PEG-NHPI) was designed and prepared in this work. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and UV-vis light spectroscopy were used to characterize PEG-NHPI. The results showed that PEG-NHPI catalysts with good water solubility and adjustable NHPI loading amounts were successfully synthesized. Using NaBr as promoter and NaClO as oxidant, PEG-NHPI mediated oxidation of cellulose was carried out and good catalytic performance was found. The catalytic performance of PEG-NHPI mediated oxidation of cellulose in water was higher than that in acetonitrile-water. The carboxyl content of PEG-NHPI oxidized cellulose could reach the level of free NHPI oxidized cellulose, and was equivalent to 68% of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) oxidized cellulose, while the degradation degree of cellulose was greatly reduced by more than 40%. The catalytic performance did not decrease significantly after six oxidation cycles. The structure of recycled PEG-NHPI was not changed. These results indicated that immobilizing NHPI onto PEG can achieve the unification of high catalytic performance and good recyclability.

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Studies in chemically modified celluloses. III. Estimation of free carboxylic acid groups in oxycellulose

Cited by 14 publications

References 14 publications

Relationship between Length and Degree of Polymerization of TEMPO-Oxidized Cellulose Nanofibrils

Relationship between Length and Degree of Polymerization of TEMPO-Oxidized Cellulose Nanofibrils

Recoverable acrylamide-vinylamine copolymer immobilized TEMPO mediated oxidation of cellulose with good catalytic performance and low cellulose degradation

Recoverable Water-soluble Polyethylene Glycol-immobilized N-hydroxyphthalimide Mediated Oxidation of Cellulose in the Presence of NaBr and NaClO

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