Surface studies of microcrystalline chitosan/poly(vinyl alcohol) mixtures

In the present study, the surface properties of microcrystalline chitosan (MCCh), poly(vinyl alcohol) (PVA) and MCCh/PVA blends (made from acetic acid solutions with the MCCh concentration ranging from 20% to 80%) have been studied by the tapping-mode atomic force microscopy (AFM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The changes of topography images are considered by determining the root mean square (RMS, Rq) deviation in the image data. For PVA samples, the transition between adjacent lamellae occurs through holes, islands, and bicontinuous structures. The AFM images showed also the lamellar structure of PVA in the blend. The crystalline topography of MCCh/PVA film surface suggests the presence of PVA on the top surface. The FTIR spectra of film blends, in the amide I and II region of MCCh and the hydroxyl stretching bands of PVA have been analyzed. FTIR analysis showed the existence of a weak interaction of the hydroxyl or amino groups of microcrystalline chitosan with hydroxyl groups of PVA.

► The surface properties were investigated by AFM, SEM and FTIR. ► The AFM images showed the lamellar structure of PVA in the blend. ► SEM microscopy confirmed the existence of microphase separation of components. ► FTIR analysis showed the existence of a weak interaction.