Effect of polymer chain end on sorption isotherm of water by chitosan

Gocho, Hiromi; Shimizu, Hiroko; Tanioka, Akihiko; Chou, Tzu-Jen; Nakajima, Toshinari

doi:10.1016/s0144-8617(99)00113-7

Cited by 73 publications

(25 citation statements)

References 15 publications

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“…1, it can be verified that the isotherms curves of chitosan presented a sigmoidal shape, which is characteristic of a glassy polymer-organic on water vapor system (Gocho, Shimizu, Tanioka, Chou, & Nakajima, 2000;Kablan, Clé ment, Françoise, & Mathias, 2008).…”

Section: Isotherms Equationsmentioning

confidence: 92%

Moisture sorption properties of chitosan

Rosa¹,

Moraes²,

Pinto³

2010

LWT - Food Science and Technology

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a b s t r a c tThe moisture equilibrium isotherms of chitosan were determined at 20, 30, 40, 50 and 60 C, using the gravimetric static method. Experimental data were analyzed by the GAB, Oswin, Halsey and Smith equations. Isosteric heat and differential entropy of sorption were determined from the GAB model using the Clausius-Clapeyron and Gibbs-Helmholtz equations, and pore size distribution was calculated by the Kelvin and Halsey equations. The GAB and Oswin equations showed best fit to the experimental data with R 2 z 99% and low mean relative deviation values (E% < 10%). Monolayer moisture content values (from 0.12 to 0.20 kg kg À1 ) and water surface area values (from 450 to 700 m 2 g À1 ) decrease with increasing temperature. Isosteric heat and differential entropy of sorption were estimated as a function of moisture content. The Kelvin and Halsey equations were adequate for calculation of pore size distribution, which varied from 0.5 to 30 nm.

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Section: Isotherms Equationsmentioning

confidence: 92%

Moisture sorption properties of chitosan

Rosa¹,

Moraes²,

Pinto³

2010

LWT - Food Science and Technology

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“…The band around 1,730 cm −1 corresponds to the ester of carboxylic group of oligo(lactic acid) existing as free or side chain (37). This suggests the presence of free lactic acid in the spray-dried chitosan lactate salt.…”

Section: Fourier Transform Infrared Spectroscopymentioning

confidence: 95%

“…This free water was not totally evaporated during spray drying. According to literature, chitosan has three predominant absorption sites: the hydroxyl group, the amino group, and the polymer chain end (37). In chitosan, the water is bound to the hydroxyl group more strongly than to the amine group.…”

Section: Near-infrared Spectroscopymentioning

confidence: 99%

Effects of Spray Drying on Physicochemical Properties of Chitosan Acid Salts

et al. 2011

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Abstract. The effects of spray-drying process and acidic solvent system on physicochemical properties of chitosan salts were investigated. Chitosan used in spray dryings was obtained by deacetylation of chitin from lobster (Panulirus argus) origin. The chitosan acid salts were prepared in a laboratory-scale spray drier, and organic acetic acid, lactic acid, and citric acid were used as solvents in the process. The physicochemical properties of chitosan salts were investigated by means of solid-state CP-MAS 13 C nuclear magnetic resonance (NMR), X-ray powder diffraction (XRPD), differential scanning calorimetry, and Fourier transform infrared spectrometry (FTIR) and near-infrared spectroscopy. The morphology of spray-dried chitosan acid salts showed tendency toward higher sphericity when higher temperatures in a spray-drying process were applied. Analysis by XRPD indicated that all chitosan acid salts studied were amorphous solids. Solid-state 13 C NMR spectra revealed the evidence of the partial conversion of chitosan acetate to chitin and also conversion to acetyl amide form which appears to be dependent on the spray-drying process. The FTIR spectra suggested that the organic acids applied in spray drying may interact with chitosan at the position of amino groups to form chitosan salts. With all three chitosan acid salts, the FTIR bands at 1,597 and 1,615 cm −1 were diminished suggesting that -NH groups are protonated. The FTIR spectra of all chitosan acid salts exhibited ammonium and carboxylate bands at 1,630 and 1,556 cm −1 , respectively. In conclusion, spray drying is a potential method of preparing acid salts from chitosan obtained by deacetylation of chitin from lobster (P. argus) origin.

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“…In literature the sigmoid curve is further interpreted by models based on Langmuir monolayer adsorption, BET (Brunauer, Emmet and Teller) multilayer adsorption, D'Arcy Watt equation, Flory-Huggins mixing theories and PEK-model (Parallel Exponential Kinetic model). 23,[43][44][45][46][47][48] These thorough moisture sorption investigations have been performed on bulk materials mainly using dynamic water vapour sorption methods and below we utilize this knowledge to further elaborate on the water uptake mechanisms taking place in our system, which exploits surface sensitive methods and ultrathin films of cellulose. At low relative humidity individual water molecules strongly bind to cellulose surface hydroxyl groups finally leading to the formation of a monolayer of water.…”

Section: Cellulose Thin Film Interactions With Water Moleculesmentioning

confidence: 99%