Formation of calcium carbonate films on chitosan substrates in the presence of polyacrylic acid

In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO₃). In the presence of high concentration of polyacrylic acid (PAA), the CaCO₃ films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO₃ films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH₂ group, whereas, for those grown on chitosan with 80% DA the CaCO₃ films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite.