An efficient, one-pot acylation of cellulose under homogeneous reaction conditions

Seoud, Omar A. El; Marson, Guilherme Andrade; Ciacco, Gabriela T.; Frollini, Elisabete

doi:10.1002/(sici)1521-3935(20000501)201:8<882::aid-macp882>3.0.co;2-i

Cited by 128 publications

(46 citation statements)

References 13 publications

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“…[10] . A presença dos grupos hidroxila na estrutura da celulose (Figura 1b, I) pode levar a agregação entre as cadeias, até mesmo em sistemas supostamente diluídos, ou seja, a celulose pode não estar presente como cadeias individualmente solvatadas, mas como agregados solvatados [11] , dificultando a obtenção de soluções "verdadeiras". Mesmo se encontrando correlações lineares entre viscosidade reduzida e concentração (figuras não mostradas), os valores da constante de Huggins (k H ) acima de 0,55 (Tabela 1), indicam que cadeias agregadas (processo irreversível), ou associadas (processo reversível) estavam presentes [10] .…”

Section: Resultsunclassified

“…Expansão das cadeias ou de estruturas associadas, devido à repulsão estérica entre os grupos acetatos, o que, em princípio aumentaria as interações polímero/solvente (LiCl/DMAc); 2. Diminuição das interações polímero/solvente, uma vez que a substituição de H pelos grupos acetatos diminuiria as interações cel-OH---Cl -, as quais são importantes no processo de solubilização da celulose em LiCl/DMAc, e provavelmente no de seus derivados [6][7][8]11] . Para os acetatos com diferentes GS, alguns valores da constante de Huggins, indicaram que cadeias agregadas, ou associadas estavam presentes.…”

Section: Resultsunclassified

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Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Morgado¹,

Martins²,

Plepis³

et al. 2011

Polímeros

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Resumo: Celulose de linter foi acetilada, visando obter acetatos de celulose com diferentes Graus de Substituição (GS) em meio homogêneo, usando cloreto de lítio/N,N-dimetilacetamida (LiCl/DMAc) como sistema de solvente, e anidrido acético como reagente acetilante. A agregação entre cadeias de celulose ou acetatos de celulose (GS 0,8, 1,5 e 2,0) em solução foi avaliada através de medidas viscosimétricas. Os resultados mostraram que a formação de agregados no sistema de solvente utilizado (LiCl/DMAc) é diferente para celulose e acetatos, e dependente da temperatura e do GS, no caso dos acetatos. Este trabalho corresponde à primeira etapa de um estudo em que se pretende preparar filmes de acetatos, assim como de acetatos reforçados com celulose, diretamente a partir de soluções destes em LiCl/DMAc. Os resultados apresentados permitem uma escolha melhor embasada do intervalo de concentração mais adequado para preparação de filmes, a partir de soluções de acetatos e celulose nesse sistema de solvente. Palavras-chave: Celulose de linter, acetato de celulose, sistema de solvente LiCl/ DMAc, agregação. Aggregation of Chains of Cellulose Acetates in LiCl/DMAc: Evaluation Via ViscometryAbstract: Linters cellulose was acetylated to obtain cellulose acetates with different degrees of substitution (DS) in homogeneous medium, using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) as solvent system, and acetic anhydride as acetylating agent. The aggregation among chains of cellulose or cellulose acetates (DS 0.8, 1.5 and 2.0) in solution was studied through viscometric measurements. The results showed that aggregation in LiCl/DMAc is different for cellulose and acetates, and depends on the temperature and DS in the case of acetates. This study corresponds to the first step of a project, which aims at to prepare cellulose acetates films, as well as acetates films reinforced with cellulose, by casting directly from these solutions in LiCl/DMAc. The results presented here allow for an optimized choice of concentration range for preparing films from LiCl/DMAc solutions of acetates and cellulose.

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Section: Resultsunclassified

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Morgado¹,

Martins²,

Plepis³

et al. 2011

Polímeros

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“…sugarcane bagasse) [2][3][4][6][7][8][9][10] mainly aiming at obtaining acetates. Cellulose derivatives, as esters, are largely industrially produced in heterogeneous medium.…”

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Sisal cellulose acetates obtained from heterogeneous reactions

Paula¹,

Lacerda²,

Frollini³

2008

Express Polym. Lett.

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In the present work, cellulose obtained from sisal, which is a source of rapid growth, was used. Cellulose acetates were produced in heterogeneous medium, using acetic anhydride as esterifying agent and iodine as catalyst, to check if the procedure described in the literature for commercial cellulose also is adequate to sisal cellulose. The results indicated that iodine is an excellent catalyst to obtain sisal cellulose acetates, but the reaction is so fast as described in the literature when, instead of sisal, lower average molar weight cellulose (microcrystalline) is used. The crystallinity index (Ic) of sisal cellulose acetates diminished compared to sisal cellulose, but there was no direct correlation between their degree of substitution (DS) and Ic. Probably acetyl groups were introduced more homogeneously along the short chains of microcrystalline cellulose, when compared to sisal cellulose, and then for microcrystalline cellulose acetates the Ic decreases as DS increases. Using the linear correlation that was found between degree of substitution (DS) and time reaction is possible to control the DS of sisal cellulose acetates, considering a large interval of degrees of substitution (0.3–2.8)

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“…The detailed method to fabricate EAPap is described in the literature. 27,36 A fabricated specimen of cellulose-based EAPap is shown in Figure 2(a). The cellulose film was coated with 40 mm 3 40 mm aluminum electrodes on both top and bottom surfaces.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Finite element analysis of vibration-driven electro-active paper energy harvester with experimental verification

Abas

Kim

Zhai

et al. 2015

Advances in Mechanical Engineering

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In this research work, a coupled-field finite element model of electro-active paper energy harvester is presented, and the results are verified experimentally. Electro-active paper is a smart form of cellulose coated with electrodes on both sides. A finite element model was developed, and harmonic and transient analyses were performed using a commercial finite element analysis package. Two 80 mm 3 50 mm and 100 mm 3 50 mm aluminum cantilever benders bonded with electro-active paper were tested to validate the finite element model results. Displacement and voltage generated by the energy harvester at the electrode surfaces were measured. The electro-active paper energy harvesters were excited at their fundamental resonance frequencies by a sinusoidal force located 18 mm from the free end. The voltage obtained from the 80 mm 3 50 mm and 100 mm 3 50 mm electro-active paper energy harvester finite element model was 3.7 and 7 mV, respectively. Experimental results have shown good agreement with the finite element model. The direct piezoelectric effect of electro-active paper shows potential for a cellulose-based eco-friendly energy harvester.

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An efficient, one-pot acylation of cellulose under homogeneous reaction conditions

Cited by 128 publications

References 13 publications

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Sisal cellulose acetates obtained from heterogeneous reactions

Finite element analysis of vibration-driven electro-active paper energy harvester with experimental verification

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