An Insight into the Role of Glycerol in Chitosan Films

RIVERO SANDRA; DAMONTE LAURA; GARCIA MARÍA A; PINOTTI ADRIANA

FOOD BIOPHYSICS

SPRINGER

Lugar: Berlin; Año: 2016 p. 1 - 11

1557-1858

This work wasfocused on assessing the influenceof the glycerol in chitosan matrices,analyzing the changes produced in the molecular mobility, mechanical, thermal,bar-rier and structural properties. The addition of glycerol in thematrixdecreased the stress values, increasing the elasticityand water vaporpermeability of the films, with a markeddecrease in glass transitiontemperature; Detailed analyses of Fourier Transform IR Spectroscopy spectrasupported the ob-served changes, especially in the spectral windows 1700-1500cm-1 revealing the modifications at molecular levelcaused byhydrogen bond interactions between chitosan andwater in the presence ofglycerol. Positron annihilation spectroscopic (PALS) measurements alloweddetermining the freevolume assuming spherical holes as well as monitoringthestructural changes in chitosan films caused by the additionof both, glyceroland water molecules. It was possible to infer that for unplasticized matrices,a sustained increase of theradius between 0.06 and 0.2 of X water  was observed, followed by a plateau up to0.35. In the other case, with the addition of glycerol, there were twoplateaus, the first between 0.25 and0.37 of X water, and the second from 0.41to 0.47. For higher glycerol concentrations, the plasticizer would be mainlybounded to the chitosan pack more efficiently and the water  present in the system would be predominantlyfree in thematrix causing its swelling. Findings on molecularmobilitycontributed to the understanding of the role of water and glyc-erol inthe structural arrangement and its influence on film properties.