Synthesis of hierarchical macro/mesoporous dicalcium phosphate monolith via epoxide-mediated sol–gel reaction from ionic precursors
- 365 Downloads
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.
KeywordsDicalcium phosphate Macroporous Mesoporous Monolith Phase separation Propylene oxide
The present work was supported by the Grant-in-Aid for Scientific Research (No. 20350094) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, and was partly supported by the Global COE Program “Integrated Materials Science” (No. B-09) of the MEXT, administrated by the Japan Society for the Promotion of Science (JSPS). Y. T. thanks the Grant-in-Aid for Fellow (No. 21-607) from JSPS. This work was partially carried out using facilities of Research Center for Low Temperature and Materials Sciences, Kyoto University.
- 17.Mullin JW (1972) Crystallisation. Butterworth, LondonGoogle Scholar
- 38.Pouchert CJ (1985) The Aldrich Library of FT-IR spectra. Aldrich Chemical Co, MilwaukeeGoogle Scholar
- 50.De Gennes PG (1979) Scaling concepts in polymer physics. Cornell University Press, New YorkGoogle Scholar
- 52.Hench LL, Wilson J (1993) Introduction to bioceramics. World Scientific, SingaporeGoogle Scholar