Size-Controlled Vaterite Composite Particles with a POSS-Core Dendrimer for the Fabrication of Calcite Thin Films by Phase Transition

Abstract

Vaterite composite particles with a size-controlled sphere were obtained by a carbonate controlled-addition method by using a carboxylate-terminated poly(amidoamine) (PAMAM)-type polyhedral oligomeric silsesquioxane (POSS)-core dendrimer. An aqueous ammonium carbonate solution was added to an aqueous solution of the dendrimer and CaCl2 at different times (3 min, 30 min, and 1 h) and stirred for 1 h at 30 °C. When the complexation time of the POSS-core dendrimer-CaCl2 solution was increased from 3 min to 1 h, the average particle sizes of the spheres increased from 0.71 ± 0.08 to 1.86 ± 0.22 μm, respectively. However, the average particle sizes decreased with decreasing temperature. Particles with minimum sizes of 70 ± 6 nm were obtained when COONa to calcium ion molar ratio was 16 and the complexation time was 3 min at 20 °C. Incubation of the vaterite composite particles in distilled water for 3 days led to complete phase transition to calcite. Negative zeta potential values, ranging from -30 to -10 mV, were detected for the vaterite particles, indicating that the POSS-core dendrimers were exposed on the CaCO3 particles. The CaCO3 particle surfaces were successfully coated with poly(diallyldimethylammonium chloride) (PDDA) in aqueous dispersions by adding a controlled concentration of the polymer. Alternate vaterite composite particles and polyelectroyte multilayer films were prepared by a layer-by-layer method. The obtained (PDDA/vaterite)10(PDDA) multilayer films were incubated in distilled water at 30 °C. Incubation for 5 days led to complete phase transition to calcite, as estimated by Fourier transform infrared (FTIR) spectroscopic and XRD analyses. The SEM observation of the sample after 5 days of incubation showed a granular network structure of irregularly shaped calcite particles. Although some patches and pores were present in the films, the SEM image clearly demonstrated that large-area and continuous CaCO3 films were formed.

Controlling the Vaterite CaCO3 Crystal Pores. Design of Tailor-Made Polymer Based Microcapsules by Hard Templating

“…Such environmental conditions as pH, ionic strength, and additives, including organic and inorganic substrates, are known to significantly affect the crystallization process of CaCO 3 crystals. − It is known from literature that temperature variation during CaCO 3 crystallization has a strong effect leading to crystallization of a certain polymorphous form. , However, no influence of the ambient temperature on the porosity of vaterite polymorphs has been reported. In this work we demonstrate that the porosity of the CaCO 3 crystals can be adjusted without any additives by means of temperature variation during the crystal growth.…”

Bendable, Free-Standing Calcite Thin Films

“…It has been reported that living organisms may use metastable forms of CaCO 3 such as amorphous CaCO 3 (ACC) or vaterite as transient precursors for the production of calcite and aragonite with hierarchically complicated structures . Although the use of an ACC precursor has been proposed as an attractive option for the biomimetic synthesis of a wide range of crystalline structures such as CaCO 3 fibers and thin films, , the use of a vaterite precursor is considered advantageous for producing calcite thin films, due to greater ease in achieving surface functionalization, size-control, and isolation. We therefore herein present a means for fabricating bendable free-standing calcite thin films through repeated cycles of layer-by-layer deposition and subsequent phase transition (Figure ).…”

Fabrication of amorphous calcium carbonate composite particles‐polymer multilayer films by a layer‐by‐layer method

“…Among various functional multilayered assemblies, much attention has been paid to fabrication of inorganic–organic hybrid films with various inorganic particles, such as magnetic , semiconductor , metal nanoparticles , and polyelectrolytes. Although the LbL assemblies of suitable CaCO 3 particles with polyelecrolytes would develop new fabrication techniques to produce CaCO 3 ‐polymer composite films in a controlled manner , ACC nanoparticles are, generally, very unstable and rapidly aggregate to big particles. Therefore, CaCO 3 layers have been prepared by conventional solution mineralization techniques on polyelectrolyte films .…”