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

作者：Nakamura Shiho; Naka Kensuke^*

来源：Langmuir, 2013, 29(51): 15888-15897.

DOI：10.1021/la403193e

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 degrees 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 mu m, 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 degrees 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 degrees 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 net-work 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.

• 出版日期2013-12-24