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%, v inyl 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 precipi tation were inversely proportional to the solution supersaturation, and a s urface energy of 23 mJm(-2) was calculated according to classical nucleatio n theory. The relatively low value may be attributed to the heterogeneous c haracter of vaterite nucleation. The linear dependence of the rates of vate rite formation on the solution supersaturation, in which the crystallizatio n took place, in combination with the independence of the measured rates on the fluid dynamics, suggested that vaterite overgrowth was controlled by s urface diffusion. This finding was in agreement with the results obtained f or 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 pl ays a role, mainly through the development of active growth sites, which sh ould show chemical and structural affinity to the mineral phase.