Title
Calcium Phosphate Mineralization in Cellulose Derivative/ Poly(acrylic acid) Composites Having a Chiral Nematic Mesomorphic Structure
Author
Takuya Ogiwara, Ayaka Katsumura, Kazuki Sugimura, Yoshikuni Teramoto, Yoshiyuki Nishio
Year
2015
Journal
Biomacromolecules
Abstract
Calcium phosphate mineralization was conducted by using polymer composites of liquid-crystalline (ethyl)cellulose (EC) or (hydroxypropyl)cellulose (HPC) with poly(acrylic acid) (PAA) as a scaffolding medium for the inorganic deposition. The EC/PAA and HPC/PAA samples were prepared in colored film form from EC and HPC lyotropic liquid crystals of left-handed and right-handed chiral nematics, respectively, by polymerization and cross-linking of acrylic acid as the main solvent component. The mineralization was allowed to proceed in a batchwise operation by soaking the liquid-crystalline films in an aqueous salt solution containing the relevant ions, Ca2+and HPO42–. The calcium phosphate-deposited EC/PAA and HPC/PAA composites (weight gain, typically 15–25% and 6–11%, respectively) retained the chiral nematic organization of the respective original handedness but exhibited selective light-reflection of longer wavelengths relative to that of the corresponding nonmineralized samples. From X-ray diffraction and energy-dispersive X-ray spectroscopy measurements, it was deduced that the calcium and phosphorus were incorporated inside the polymer matrices in three forms: amorphous calcium phosphate, hydroxyapatite, and a certain complex of PAA-Ca2+. Dynamic mechanical analysis and thermogravimetry revealed that the inorganic hybridization remarkably enhanced the thermal and mechanical performance of the optically functionalized cellulosic/synthetic polymer composites; however, the effect was more drastic in the EC/PAA series rather than the HPC/PAA series, reflecting the difference in the deposited mineral amount between the two.
Instrument
J-820
Keywords
Circular dichroism, Materials