title: 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.
authors: Department of Chemistry and Materials Technology, Graduate School of Science and Technology, Kyoto Institute of Technology , Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
authors: Shiho
authors: S
authors: Nakamura
authors: Kensuke
authors: K
authors: Naka
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D002122:Calcium Chloride / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D017646:Organosilicon Compounds / Q000737:chemistry*; D010316:Particle Size; D011073:Polyamines / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D050091:Dendrimers; D017646:Organosilicon Compounds; C531249:Poly(amidoamine); D011073:Polyamines; D014867:Water; D002119:Calcium Carbonate; D002122:Calcium Chloride