Miscibility Study of Chitosan/Poly(Vinyl Pyrrolidone) Blends in Dilute Solution

Miscibility of chitosan (CHI) with two poly(vinyl pyrrolidone) samples (PVP-1 and PVP-2) of different molecular weights was studied in dilute solution by viscometry. Blends with chitosan weight fraction in the range 0.10–0.90 were studied at 30°C in a buffer solution of 0.1 M acetic acid/0.2 M sodium acetate. Starting with the classical Huggins equation, the results of the viscosity behavior of each parent polymer and their blends were interpreted in terms of miscibility parameters, Δk, α, and Δb. CHI (Mv = 3.3 × 105) and PVP-1 (Mv = 2.5 × 104) were found to be miscible at a blend composition of CHI/PVP 0.90/0.10. PVP-2 (Mv = 1.1 × 106) and CHI were miscible in the full range of blend compositions studied. The existence of favorable secondary interaction between CHI and PVP leading to miscibility was demonstrated by FTIR spectroscopy.