Use of ATR FT-IR spectroscopy technique to determine the crosslinking density of chitosan film at various depths

Abstract

Crosslinking density of chitosan films plays an important role in the properties of chitosan films. However, there are only small numbers of researches, which determine the crosslinking density at various depths. The objective of this research is to determine the crosslinking density at various depths of chitosan films crosslinked with glutaraldehyde by heterogeneous procedure. The technique used to determine the crosslinking density was attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. By varying the angles of incidence and performing mathematical operation on the observed spectra, the information at various depths of the films in terms of nk values were achieved. The results showed that the crosslinking density was not uniform over the entire thickness of the film. The crosslinking density was highest at the surface, which contacted directly with crosslinking solution and decreased as a function of depth. Moreover, it was found that crosslinking reaction was occurred at the 10 um depths from crosslinked surface.