Flexible chitin films : structural studies

Chitin gels were transformed into thin, flexible chitin films with minimal dimensional shrinkage and maximum flexibility and thickness in the range of 25-80 mum by a cold-press process. Solvent residue was removed by heating the films at 50degreesC for 12 h, followed by rinsing in 95% ethanol. The crystallinity and mechanical properties of the flexible chitin films were found to be a function of the amount of shrinkage from the gel to the final film that was obtained. For 28-mum thick films with 30% shrinkage, transparency of up to 90% was found. X-ray diffractometry (XRD) showed that the number of diffraction peaks appearing at 2theta = 23degrees and 2theta = 27degrees became increasingly sharper with shrinkage. Topographical information obtained from scanning electron microscopy (SEM) and atomic force microscopy (AFM) attributed the structural morphology of the films to the formation of sub-microscopic micelles. Scanning transmission electron microscopy (STEM) showed that shrinkage resulted in coarser microstructure, affecting tensile properties, where the ductility and toughness were proportional to the amount of shrinkage. These flexible chitin films have potential as wound dressing materials. (C) 2004 Elsevier Ltd. All rights reserved.