Original Paper

Journal of Sol-Gel Science and Technology

, Volume 57, Issue 3, pp 269-278

First online:

Synthesis of hierarchical macro/mesoporous dicalcium phosphate monolith via epoxide-mediated sol–gel reaction from ionic precursors

  • Yasuaki TokudomeAffiliated withDepartment of Chemistry, Graduate School of Science, Kyoto University
  • , Akira MiyasakaAffiliated withDepartment of Chemistry, Graduate School of Science, Kyoto University
  • , Kazuki NakanishiAffiliated withDepartment of Chemistry, Graduate School of Science, Kyoto University Email author 
  • , Teiichi HanadaAffiliated withDepartment of Chemistry, Graduate School of Science, Kyoto University

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Abstract

Starting from calcium chloride dihydrate (CaCl2·2H2O), phosphoric acid (H3PO4), and poly(acrylic acid) (PAA) dissolved in a mixture of water and methanol (MeOH), dicalcium phosphate anhydrous (DCPA, CaHPO4) monoliths with co-continuous macropores and mesopores have been synthesized by the addition of propylene oxide. Macropores are formed as a result of phase separation, while mesopores as interstices between primary particles with the size of ca. 30 nm. Propylene oxide acts as a proton scavenger and leads to moderate pH increase in a reaction solution, which brings about gelation in several minutes. On the other hand, PAA acts as a crystal growth inhibitor as well as a phase separation inducer. The extensive crystal growth of DCPA is hindered by the addition of PAA which allows morphological control of the structure in micrometer range. Fourier transform infrared spectroscopy indicates that PAA and DCPA form composite via interaction between the carboxyl groups and the surface of crystals, and together form gel phase. The solvent phase, which is converted to macropores after evaporative drying, is mainly comprised of solvent. The degree of supersaturation in a reaction solution considerably influence on the crystallization process, and thereby, influences on the porous structure in nano- and micrometer ranges.

Keywords

Dicalcium phosphate Macroporous Mesoporous Monolith Phase separation Propylene oxide