An Insight into the Role of Glycerol in Chitosan Films

S.RIVERO; L.C. DAMONTE; M.A.GARCIA; A.PINOTTI

FOOD BIOPHYSICS

SPRINGER

Lugar: Berlin; Año: 2016

1557-1858

This work was focused on assessing the influence of the glycerol in chitosan matrices,analyzing the changes produced in the molecular mobility, mechanical, thermal, barrierand structural properties.The addition of glycerol in the matrix decreased the stress values, increasing theelasticity and water vapor permeability of the films, with a marked decrease in glasstransition temperature; Detailed analyses of Fourier Transform IR Spectroscopyspectra supported the observed changes, especially in the spectral windows 1700-1500 cm-1 revealing the modifications at molecular level caused by hydrogen bondinteractions between chitosan and water in the presence of glycerol. Positronannihilation spectroscopic (PALS) measurements allowed determining the free volumeassuming spherical holes as well as monitoring the structural changes in chitosan filmscaused by the addition of both, glycerol and water molecules. It was possible to inferthat for unplasticized matrices, a sustained increase of the radius between 0.06 and0.2 was observed, followed by a plateau up to 0.35. In the other case, with the additionof glycerol, there were two plateaus, the first between 0.25 and 0.37, and the secondfrom 0.41 to 0.47.For higher glycerol concentrations, the plasticizer would be mainly bounded to thechitosan pack more efficiently and the water present in the system would bepredominantly free in the matrix causing its swelling. Findings on molecular mobilitycontributed to the understanding of the role of water and glycerol in the structuralarrangement and its influence on film properties.