Relationship between molecular mobility, microstructure and functional properties in chitosan/glycerol films

Foods are partially crystalline partially amorphous systems. Edible films are considered good models for food systems due to their interesting physical properties, quite straightforward matrices, and easy reproduction. Chitosan is a semicrystalline biopolymer, biocompatible, biodegradable, with antimicrobial activity and filmogenic properties, and it has been thoroughly used in edible films studies. The purpose of this work is to investigate the relationship between the molecular relaxation time in chitosan films, their microstructure (crystallinity) and functional properties. Analyses were carried out using data on chitosan/ glycerol films prepared with different polymer/ plasticisant concentration. In general, results demonstrate that there is a relationship between macroscopic properties and water and glycerol relaxation times. Moreover, results also show that while water is free in the matrix, glycerol is linked to the chitosan polymeric chains, decreasing intermolecular attractions and increasing free volume, thus facilitating molecular migration. Also the data analysis reveals the usefulness of NMR and molecular mobility studies in the matrix for characterisation and development of polymeric structures.
Authors Joana F. Fundo and Mafalda A. C. Quintas acknowledge FCT for research grants SFRH/BD/62176/2009 and SFRH/BPD/41715/2007, respectively. The authors acknowledge the Portuguese NMR Network and Strategic Project PEst-C/CTM/LA0025/2013-14 and the support by National Funds from FCT through project PEst-OE/EQB/LA0016/2011.