Effect of lactic/glycolic acid side chains on the thermal degradation kinetics of chitosan derivatives

Qu, Xin; Wirsén, Anders; Albertsson, Ann‐Christine

doi:10.1016/s0032-3861(99)00704-1

Cited by 189 publications

(84 citation statements)

References 12 publications

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“…The major thermal processes occurred between 50 and 350°C. The broad endothermic peak between 50 and 200°C can be attributed to the evaporation of water bonded to the chitosan chains and functional groups of cross-linking agents by different kinds of physical bonds (hydrogen bonds, electrostatic interactions) [18,19]. Chitosan membrane underwent exothermic decomposition at higher temperatures.…”

Section: Thermal Properties Of Hydrogel Membranesmentioning

confidence: 99%

“…The exothermic peak appeared at 301, 218 and 201°C for Ch, Ch/GA and Ch/GA/SA membrane, respectively. This peak corresponds to degradation of chitosan [18,19]. In the case of cross-linked membranes DSC thermograms are more complex, because additional exothermic and endothermic peaks are observed at temperatures above 200°C.…”

Section: Thermal Properties Of Hydrogel Membranesmentioning

confidence: 99%

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pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

2015

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pH-responsive membranes prepared by treating chitosan (Ch) with glutaraldehyde (GA) or with GA and sulfuric acid (SA) were studied. The structure and properties of the membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis. The effect of the cross-linking process both on the dynamic swelling behaviour of the hydrogel membranes and on the mechanism of water transport through those membranes was investigated in buffer solutions of different pH (1.2-9.5). The mechanism of water transport through the hydrogel chitosan membranes was affected by membrane composition and pH of the swelling medium. Non-cross-linked Ch membrane showed a non-Fickian swelling behaviour in the pH range 6.5-9.5. Chitosan membrane cross-linked with GA (Ch/GA) showed less-Fickian or Fickian swelling behaviour in all buffer solutions. In the case of chitosan membrane cross-linked with GA and SA (Ch/GA/SA), at low pH (lower than the pK a of the hydrogel) the water transport was controlled more by polymer relaxation than by penetrant diffusion. The experimental data clearly suggested that the swelling process in all buffer solutions obeyed second-order kinetics. Values of an apparent swelling rate constant for Ch/ GA and Ch/GA/SA membranes were of the same order of magnitude for acidic and neutral swelling media but they increased for alkaline solutions.

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Section: Thermal Properties Of Hydrogel Membranesmentioning

confidence: 99%

Section: Thermal Properties Of Hydrogel Membranesmentioning

confidence: 99%

pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

2015

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“…Levoglucosan formation from cellulose pyrolysis is produced by the scission of the 1,4 glucosidic linkage in the cellulose, followed by intramolecular rearrangement of the monomer units [46] .…”

Section: Characterization Of Cellulose Acetatesmentioning

confidence: 99%

“…The Ea were determined from the slopes of the obtained linear curves (Figure 4) [46] . Similar curves were obtained for the other cellulose acetates (figures not shown).…”

Section: Characterization Of Cellulose Acetatesmentioning

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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“…This is similar to the results reported by other researchers. [14][15][16] From the TGA and DTG results, the degradation mechanisms of the polymer matrices and their nanocomposites clearly are somehow different, corresponding to the different structures of the polymers and nanocomposites.…”

Section: Thermal Stabilitymentioning

confidence: 99%

Structure–property relationship in chitosan‐based biopolymer/montmorillonite nanocomposites

Wang

Chen

Tong

2005

J. Polym. Sci. A Polym. Chem.

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Effect of lactic/glycolic acid side chains on the thermal degradation kinetics of chitosan derivatives

Cited by 189 publications

References 12 publications

pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

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

Structure–property relationship in chitosan‐based biopolymer/montmorillonite nanocomposites

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