Surface modification of hydroxyapatite. Part I. Dodecyl alcohol

Area of Science:

• Materials Science
• Surface Chemistry
• Colloid Science

Background:

• Hydroxyapatite (HAP) is a key biomaterial, but its surface chemistry and colloid stability are critical for applications.
• Understanding surface modification is essential for controlling HAP's behavior in various environments.

Purpose of the Study:

• To investigate the impact of esterification reactions on hydroxyapatite (HAP) surface chemistry.
• To evaluate how dodecyl alcohol modification affects the colloid stability of nanophase HAP.

Main Methods:

• Nanophase HAP was aged in dodecyl alcohol at elevated temperatures (115°C and 190°C).
• Characterization included X-ray diffraction, transmission electron microscopy, DRIFTS, TGA, sedimentation studies, and electrophoretic mobility.
• Diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS) confirmed surface dodecyl group modification via C-H stretch vibrations.

Main Results:

• DRIFTS confirmed surface modification with dodecyl groups.
• Esterified HAP showed increased thermal mass loss (up to 4.8%) compared to untreated HAP (2.5-3.2wt%).
• Colloid stability in ethyl alcohol significantly increased for esterified HAP (over 65 days) compared to untreated HAP (1-7 days).

Conclusions:

• Esterification of HAP with dodecyl alcohol alters its surface chemistry.
• Surface dodecyl groups provide steric stabilization, significantly enhancing HAP colloid stability in ethyl alcohol.
• Lewis acid/base interactions influence untreated HAP stability, while steric effects dominate for modified HAP.