Alginate-magnesium aluminum silicate films: Importance of alginate block structures

Sodium alginate-magnesium aluminum silicate (SA-MAS) composite dispersions were prepared and characterized for the flow behavior and morphology of their dispersed phase before casting. The high G block and high M block SA (GSA and MSA, respectively) were used. The physicochemical properties and permeabilities of the films were investigated using non-electrolyte and amine compounds in an acidic medium. The results showed that incorporation of MAS into the GSA and MSA dispersions gave identical flow behaviors and morphologies of MAS flocculates. FTIR spectroscopy revealed that the GSA and MSA presented similar molecular interactions with MAS in the films. However, the crystallinity of the GSA-MAS films was possibly higher than that of the MSA-MAS films. This indicated a higher density of matrix structure formed between GSA and MAS, resulting in lower water uptake in an acidic medium. Consequently, the permeability of the GSA-MAS films was lower than that of the MSA-MAS films. The diffusion and partition coefficients were directly related to the molecular weight of the non-electrolyte and amine compounds. This study suggested that transport of non-electrolyte compounds was predominantly controlled by diffusion in aqueous-filled microchannels, whereas both partition via adsorption onto MAS and diffusion in microchannels occurred concurrently for amine compounds. (C) 2008 Elsevier B.V. All rights reserved.