Correlations between the free-volume properties and the miscibility of chitosan/polar polymers blend membranes

The miscibility of chitosan (CS)/polar polymer blend membranes has been studied by positron annihilation and other methods. The miscibility of these two blend systems (CS/polyvinyl pyrrolidone (PVP) and CS/polyethylene glycol (PEG)) is good in the solution state due to the hydrogen interaction between the functional groups of the studied polymers. However, the miscibility of these two blend systems in the solid state is better in the CS/PVP system than in the CS/PEG system. The differences in miscibility of such two blend systems in the solid state were powerfully demonstrated with positron annihilation lifetime spectroscopy (PALS) methods. The CS/PEG blend system had much larger free-volume size and lower free-volume concentration. For their poorer interaction and phase separation fact, the molecules in the interfacial zone of the CS/PEG blend are less compact than the CS matrix. Therefore, the free-volume size in the interfacial zone was much larger than it in the CS matrix