Homogeneous esterification of cellulose in the lithium chloride–N,N-dimethylacetamide solvent system: effect of temperature and catalyst

Tosh, Biranchinarayan; Saikia, C. N.; Dass, N. N.

doi:10.1016/s0008-6215(00)00033-1

Cited by 103 publications

(73 citation statements)

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“…However, a suitable method to dissolve cellulose owing to its high crystallinity and polymerization (DP) as well as ultra-strong inter-and intramolecular hydrogen bonds is pivotal for fabricating an environmentally sustainable aerogel [17,18]. Many effective cellulose solvents have been proposed such asionic liquid [19][20][21], N-methylmorpholine-N-oxide (NMMO) [22], lithium chloride/N,N-dimethylacetamide (LiCl/ DMAC) [23], NaOH/urea [24,25] and NH 3 /NH 4 SCN [26]. Nevertheless, most of these are limited by their high cost, toxicity or volatility.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of cellulose aerogel from wheat straw with strong absorptive capacity

Li¹,

Wan²,

Lu³

et al. 2014

Front. Agr. Sci. Eng.

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An effectively mild solvent solution containing NaOH/PEG was employed to dissolve the cellulose extracted from the wheat straw. With further combined regeneration process and freeze-drying, the cellulose aerogel was successfully obtained. Scanning electron microscope, X-ray diffraction technique, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller were used to characterize this cellulose aerogel of low density (about 40 mg$cm ). Additionally, with a hydrophobic modification by trimethylchlorosilane, the cellulose aerogel showed a strong absorptive capacity for oil and dye solutions.

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Section: Introductionmentioning

confidence: 99%

Fabrication of cellulose aerogel from wheat straw with strong absorptive capacity

Li¹,

Wan²,

Lu³

et al. 2014

Front. Agr. Sci. Eng.

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“…The aprotic polar solvent (N,N-dimethylacetamide) in combination with an inorganic salt, preferably lithium chloride (LiCl) [6] , is able to dissolve cellulose. The impetus behind investigating this solvent system for cellulose derivatization under homogeneous reaction has been extensively described in the literature [7][8][9][10][11][12][13] . The homogeneous reaction involves several steps, including cellulose activation, dissolution, and subsequent reaction with a derivatizing agent [10] .…”

Section: Introductionmentioning

confidence: 99%

Thermal decomposition of mercerized linter cellulose and its acetates obtained from a homogeneous reaction

Morgado

Frollini

2011

Polímeros

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Abstract:Cellulose acetates with different degrees of substitution (DS, from 0.6 to 1.9) were prepared from previously mercerized linter cellulose, in a homogeneous medium, using N,N-dimethylacetamide/lithium chloride as a solvent system. The influence of different degrees of substitution on the properties of cellulose acetates was investigated using thermogravimetric analyses (TGA). Quantitative methods were applied to the thermogravimetric curves in order to determine the apparent activation energy (Ea) related to the thermal decomposition of untreated and mercerized celluloses and cellulose acetates. Ea values were calculated using Broido's method and considering dynamic conditions. Ea values of 158 and 187 kJ mol -1 were obtained for untreated and mercerized cellulose, respectively. A previous study showed that C6OH is the most reactive site for acetylation, probably due to the steric hindrance of C2 and C3. The C6OH takes part in the first step of cellulose decomposition, leading to the formation of levoglucosan and, when it is changed to C6OCOCH 3 , the results indicate that the mechanism of thermal decomposition changes to one with a lower Ea. A linear correlation between Ea and the DS of the acetates prepared in the present work was identified. Keywords: Linter cellulose, cellulose acetates, thermal decomposition. Decomposição Térmica de Celulose de Linter Mercerizado e seus Acetatos Obtidos a partir de Reação HomogêneaResumo: Acetatos de celulose com graus de substituição, GS, variando entre 0,6 e 1,9, foram preparados previamente a partir de celulose de linter mercerizado, em meio homogêneo, usando N,N-dimetilacetamida/cloreto de lítio como sistema de solvente. A influência de diferentes graus de substituição nas propriedades dos acetatos de celulose foi investigada usando a análise termogravimétrica (TGA). Métodos quantitativos foram aplicados nas curvas termogravimétricas obtidas a fim de determinar a energia de ativação aparente (Ea) relacionado à decomposição térmica de celulose não-tratada e mercerizada e acetatos de celulose. Valores de Ea foram calculados usando o método de Broido e considerando condições dinâmicas. Valores de Ea de 158 e 187 kJ mol -1 foram obtidos para a celulose não-tratada e mercerizada, respectivamente. Em trabalho anterior verificou-se que o C6OH é o sítio mais reativo na acetilação, provavelmente devido ao impedimento estérico de C2 e C3. O C6OH participa da primeira etapa de decomposição da celulose, levando à formação de levoglucosana e, quando se tem a substituição para C6OCOCH 3 , o resultado indica que o mecanismo de decomposição térmica muda para um com Ea menor. Uma correlação linear entre Ea e o GS dos acetatos preparados no presente trabalho foi identificada. Palavras-chave: Celulose de linter, acetatos de celulose, decomposição térmica.

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“…Synthesis of the APM and BPM APM was prepared by the method of Tosh et al (2000) with minor modification. Briefly, a mixture of PM (2 g) and N, N-dimethylacetamide (DMAc, 80 mL) was heated at 150 °C for 30 min.…”

Section: Methodsmentioning

confidence: 99%

“…The polysaccharide named as PM extracted from the Ramulus mori was used. The polysaccharide was, respectively, sulfated, phosphorylated, acetylated and benzoylated to obtain four water-soluble derivatives coded as sample SPM, PPM, APM, and BPM respectively here.Synthesis of the APM and BPM APM was prepared by the method of Tosh et al (2000) with minor modification. Briefly, a mixture of PM (2 g) and N, N-dimethylacetamide (DMAc, 80 mL) was heated at 150 °C for 30 min.…”

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confidence: 99%

Antioxidant Activity of the Derivatives of Polysaccharide Extracted from a Chinese Medical Herb (Ramulus mori)

Zhang

Jin

Shi

2008

FSTR

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The antioxidant activity of the polysaccharide from Ramulus mori and its derivatives (sulfated, phosphorylated, acetylated and benzoylated polysaccharides) were determined, including scavenging activity against superoxide, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals, reducing power and chelating ability. Obvious differences in antioxidant activity between the natural polysaccharide and its derivatives were observed, the antioxidant activity of the sulfated, phosphorylated and acetylated derivatives was stronger than that of the natural polysaccharide. In addition, the effect of temperature (20, 40, 60, 80 and 90 °C) and pH (3, 5, 7, 9 and 11) on the antioxidant activity of the natural polysaccharide and its derivatives was also investigated. The antioxidant activity of all samples in the linoleate emulsion improved with increasing from pH 3 to 11, while it decreased with ascending storage temperature from 20 to 90 °C.Keywords: antioxidant activity, temperature, pH, polysaccharide derivatives, Ramulus mori *To whom correspondence should be addressed. Email: slgsilk@zju.edu.cn IntroductionReactive oxygen species (ROS) produced by sunlight, ultraviolet light, ionizing radiation, chemical reactions and metabolic processes have a wide variety of pathological effects, such as causing DNA damage, carcinogenesis and cellular degeneration related to aging (Blander et al., 2003). In order to reduce damage of free radicals, synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propylgallate (PG), and tert-butylhydroquinone (TBHQ) are used. However, BHA and BHT have been suspected of being responsible for liver damage and carcinogenesis (Grice, 1988). Thus, it is essential to develop and utilize effective and natural antioxidants so that they can protect the human body from free radicals and retard the progress of many chronic diseases (Nandita and Rajini, 2004).Polysaccharides are common structural and storage polymers in living organisms, representing more than 75 % of the dry mass of plants. Polysaccharides are potentially useful, biologically active ingredients for pharmaceutical uses due to a variety of biological activities, such as immunological, anti-radiation, anti-blood coagulation, anti-cancer, anti-HIV and hypoglycemic activities (Yang et al., 2005;Yoon et al., 2003;Lee et al., 2002). The activity of polysaccharides is close related to their structure such as molecular mass, degree of substitution, degree of branching, sugar component and the structures of main chain and branches (Bohn and BeMiller, 1995). Thus, chemical modifications of polysaccharides provided an opportunity to obtain new agents with possible therapeutic uses (Franz and Alban, 1995).Ramulus mori is the branch of Morus alba L., family Moraceae, according to the theories of traditional Chinese medicine, it is slightly bitter in taste, mild in nature, and attributive to the liver meridian. In traditional Chinese medicine, its pharmacological actions are to expel wind, dredge the meridians, and ease...

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Homogeneous esterification of cellulose in the lithium chloride–N,N-dimethylacetamide solvent system: effect of temperature and catalyst

Cited by 103 publications

References 5 publications

Fabrication of cellulose aerogel from wheat straw with strong absorptive capacity

Fabrication of cellulose aerogel from wheat straw with strong absorptive capacity

Thermal decomposition of mercerized linter cellulose and its acetates obtained from a homogeneous reaction

Antioxidant Activity of the Derivatives of Polysaccharide Extracted from a Chinese Medical Herb (Ramulus mori)

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