The overgrowth of calcium carbonate on poly(vinyl chloride-co-vinyl acetate-co-maleic acid)

Poly(vinyl chloride-co-vinyl acetate-co-maleic acid) (vinyl chloride 83%, vinyl acetate 13%, carboxylated 1%) was found to be a substrate favoring the deposition of vaterite crystals from stable supersaturated solutions at pH 8.50 and 25 degrees C. Induction times preceding calcium carbonate precipitation were inversely proportional to the solution supersaturation, and a surface energy of 23 mJm(-2) was calculated according to classical nucleation theory. The relatively low value may be attributed to the heterogeneous character of vaterite nucleation. The linear dependence of the rates of vaterite formation on the solution supersaturation, in which the crystallization took place, in combination with the independence of the measured rates on the fluid dynamics, suggested that vaterite overgrowth was controlled by surface diffusion. This finding was in agreement with the results obtained for the crystallization of vaterite on cholesterol. Our results suggest that the kinetics of overgrowth may be very important for the stabilization of transient mineral phases. The structure of the polymeric substrates also plays a role, mainly through the development of active growth sites, which should show chemical and structural affinity to the mineral phase.