Molecular simulation and experimental studies of the miscibility of chitosan/poly(ethylene oxide) blends

The miscibility of chitosan/poly(ethylene oxide) (CS/PEO) blends was investigated by a combination of experiment and molecular simulation. Results from X-ray diffraction (WAXD) and thermal analysis (DSC) suggest that the maximum miscibility was seen at the PEO weight fraction (w(PEO)) = 0.2; the optimum stoichiometric ratio for CS and PEO functional groups. The change in vibrational frequencies from infrared spectra was attributed to the specific interaction between PEO ether oxygen with the amino and hydroxyl groups of CS. Radial distribution functions (RDF) from MD simulation suggest that all CS functional groups (NH2, C-3-OH, and C6-OH) can interact with PEO ether groups for which NH2 has the highest activity. For CS hydroxyl groups, a more significant contribution of C6-OH rather than C3-OH groups that interact with PEO ether oxygen was observed. The interaction parameter (chi) determined from MD simulation was in good agreement with that of the DSC experiment (chi(CS-PEO)=-0.21). Based on a comparison between chi and chi(critical), CS/PEO blend was predicted to be miscible for w(PEO) <0.58 with a maximum at w(PEO) =0.2. In addition, the order parameter from the mesoscale simulation was employed to monitor the phase separation in these blends. From MesoDyn simulation, the miscibility was decreased with increasing PEO content, and miscible CS/PEO blends were obtained only with w(PEO) <0.58, in good agreement with MD simulation and experiment.