Sorption and transport of water vapor in alginic acid, sodium alginate, and alginate‐cobalt complex films

Abstract

The sorption and the transport of water vapor in films of alginic acid (G1), sodium alginate (G1Na), and alginate‐cobalt complex (G1Co) were studied at 30°C by employing the weighing method. Sorption isotherms for all films of G1, G1Na, G1Co were of type II in the Brunauer's classification. The integral absorption from, and desorption to, zero pressure were non‐Fickian type for all films studied. The mean permeability coefficient P, which was determined by the cup method, increased with the increase of vapor pressure, especially in the low vapor pressure region. P for G1Na was much higher than that for G1, which mainly reflects more hygroscopic nature of G1Na than that of G1. The values of P for G1Co were lower than those for G1 at lower pressures and then approached those for G1 at higher vapor pressures. Integral diffusion coefficient D evaluated as P/S, where the solubility coefficient S was evaluated from sorption isotherms, increased rapidly with increasing water concentration and then leveled off. In the concentration region studied, the magnitude of D and its dependence on concentration for H2O‐G1Na system did not differ much from those for H2O‐G1 system. D for H2O‐G1Co system was much lower than that for H2O‐G1 system. © 1994 John Wiley & Sons, Inc.

Water Sorption and Diffusion in (Reduced) Graphene Oxide‐Alginate Biopolymer Nanocomposites

“…Figure illustrates representative moisture sorption data (open symbols). All moisture sorption curves of alginate composites showed a distinctive sigmoidal shape, indicating a non‐Fickian water vapor diffusion mechanism in the composite films, previously also observed for alginate films . In an attempt to model and quantify water diffusion in alginates and their composites, the Variable Surface Concentration Model was used to fit the experimental data (solid lines).…”

Alginate Nanofibrous Mats with Adjustable Degradation Rate for Regenerative Medicine

“…In particular, the stability of the treated nanofibres in aqueous media is directly related to the amount of poly(alginic acid) 13 produced during the TFA process. In fact, it is well known that alginic acid is insoluble in water 29 and it has low water sorption 29b, 30 . As shown in Figure 2B, the ratio  COOH / aC-O-C , which can be considered an indication of the presence of alginic acid in the nanofibres, is maximised for 12 or 24 h of acid treatment.…”

The Entropic Mechanism of Water Solvation of Polymers

“…The same coefficients for water in cellulose (25°C) [18] equal to 0.29, 2000, 0.7, respectively. For alginic acid (which main difference from cellulose is in the presence of a COOH-group instead of CH2.0H), studied in the work [19] (30"C), these coefficients are 0.428, 1200 and 0.6, respectively. Salts (sodium and cobalt) of alginic acid possess higher hydrophilic nature [19].…”

“…It should be noted that formation of drops of free water is observed in the same polymers under quite high humidity [17,[19][20][21], but this does not affect coefficients of the TBFM equation.…”