Composites between hydroxyapatite and poly(epsilon-caprolactone) synthesized in open system at room temperature

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Surface Chemistry

Background:

• Hydroxyapatite (HA) is a key biomaterial for bone regeneration.
• Improving the organic-inorganic interface in HA composites is crucial for performance.
• Surface functionalization of HA can enhance its integration with polymers.

Purpose of the Study:

• To investigate the surface-initiated polymerization of epsilon-caprolactone (CL) on hydroxyapatite (HA).
• To characterize the resulting poly(epsilon-caprolactone) (PCL) and its bonding to HA.
• To determine the effect of HA annealing temperature on PCL formation and bonding.

Main Methods:

• Polymerization of CL initiated by HA hydroxyls at room temperature and elevated temperatures.
• Characterization of ionically bonded and free PCL fractions.
• Analysis of PCL properties based on HA annealing temperatures (700°C, 900°C, 1,100°C).

Main Results:

• HA hydroxyls initiate CL polymerization, forming an ionically linked polymer layer on the HA surface.
• The annealing temperature of HA significantly influences the ratio of ionically bonded to free PCL.
• HA annealed at 1,100°C is the most effective initiator for ionically bonded PCL formation.
• Higher percentages of free PCL are observed at room temperature, influenced by water and HA composition.

Conclusions:

• Surface hydroxyls on HA can effectively initiate PCL polymerization, enhancing composite compatibility.
• Optimizing HA annealing temperature is critical for controlling PCL bonding and properties.
• Water plays a role in free PCL formation, suggesting controlled environments may favor bonded PCL.