DOI: 10.1021/cg900721g
In Situ Atomic Force Microscopy Study on the Crystallization of Calcium Carbonate Modulated by Poly(vinyl alcohol)s
2009, Vol. 9 4584–4587
Raehyun Kim,† Chulki Kim,‡ Sangsoo Lee,† Junkyung Kim,† and Il Won Kim*,‡ †
Hybrid Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea, and ‡Department of Chemical and Environmental Engineering, Soongsil University, Seoul 156-743, Korea Received June 26, 2009; Revised Manuscript Received September 19, 2009
ABSTRACT: The effect of poly(vinyl alcohol) (PVA) on the crystallization of calcium carbonate is reported. Crystallization was initiated by flowing a supersaturated solution over a single crystal of calcite, and in situ atomic force microscopy (AFM) was utilized to observe the crystal growth. When no additives were in the supersaturated solution, typical step growth at the screw dislocation hillocks of calcite proceeded. When poly(ethylene oxide), poly(N-vinyl pyrrolidone), and poly(N-isopropyl acrylamide) were added to the solution, a similar behavior was observed. However, with PVA, dramatic changes occurred in the crystal growth. PVA initially induced step roughening, followed by step bunching, which led to macrostep formation. More importantly, PVA promoted two-dimensional (2D) nucleation and growth, which extensively affected the entire crystallization region. The change in growth mode, from step-flow initiating from dislocations to 2D island formation, originates from the PVA adsorption. The adsorbed PVA inhibits the advance of calcite steps and induces 2D island formation, together leading to a new surface morphology. The extensive 2D island formation with a macromolecular additive, but without a preorganized organic matrix, seems to be a technically attractive strategy to generate assembled microcrystals with occluded macromolecules, a structure well-known in biomineralization. Biomineralization is the controlled formation of inorganic mineral phases, in part, regulated by organic macromolecules.1-3 The control processes have been the subject of intense studies because of the possibility of uncovering new paradigms of materials development.3-5 Special interests have been directed to the extraordinary influence that low concentrations (
