Search

The compatibility of chitosan (CS) and poly(vinyl pyrrolidone) was investigated by molecular dynamic (MD) simulations using the Flory–Huggins theory. The specific interactions in blends were studied by the radial distribution function (RDF). The Flory–Huggins interaction parameter, χ, was calculated at 298 K to assess the blend compatibility at different component ratios in the polymers. Miscibility was observed for blends with more than 50% of CS in the molar fraction, while immiscibility was prevalent at the molar fraction of CS between 10 and 50% of CS. Miscibility between poly(N-vinyl-2-pyrrolidone) (PVP) and CS polymers is attributed to the hydrogen bond formation of the –C = O group of PVP and the –CH2OH groups of CS. This was further confirmed by MD simulations of RDFs for groups or atoms that are involved in interactions. These results are correlated well to obtain more realistic information on interactions involved as a function of blend composition.

The effect of temperatures and NaCl concentrations on the structures of polyampholyte(carboxyethyl chitosan) under different pH conditions were investigated using molecular dynamics simulations. The radius of gyration (ROG) of the backbone Cα of carboxyethyl chitosan was analyzed and the accessible surface areas (ASA) of entire polyampholytes were estimated. The variation of the ROG and the ASA of polyampholyte with temperatures and different NaCl concentrations under different pH conditions are discussed. The present simulation makes it possible to understand the structures of polyampholyte in aqueous solutions at the molecular level.