Synergistic role of ultrasonication and polymer functionalization in stabilizing hydroxyapatite/CNT nanocomposites

The development of stable hydroxyapatite (HAp)-based nanocomposites with enhanced dispersion and long-term stability is essential for advanced bioceramic applications. In this study, an ultrasound-assisted polymer functionalization strategy was employed to fabricate hydroxyapatite/carboxylated carbon nanotube (HAp/CNT-COOH) nanocomposites stabilized within a poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEPE) matrix. Ultrasonication at 20 kHz for 180 min effectively reduced the hydrodynamic particle size from 1715 nm to 308 nm and decreased the polydispersity index from 0.914 to 0.259 in optimized samples. The zeta potential improved to −30.1 mV, indicating enhanced electrostatic stability, while ultraviolet–visible absorbance increased by over 60 %, confirming superior dispersion. X-ray diffraction confirmed the retention of the HAp crystalline phase, and Fourier transform infrared and Raman spectroscopy evidenced strong interfacial bonding between HAp, CNTs, and PEPE. Thermal analysis showed an increase in the degradation temperature from 382 °C (neat PEPE) to 390 °C in the composites, signifying improved thermal resistance. Furthermore, colloidal stability was maintained for over four weeks with minimal sedimentation. These results demonstrate the synergistic role of ultrasonication and amphiphilic polymer stabilization in producing well-dispersed, thermally stable HAp/CNT nanocomposites, offering scalable potential for bioceramic coatings, load-bearing scaffolds, and bone tissue engineering applications.