Enhanced colloidal stability of hydroxyapatite by the adsorption of a polymer containing a quaternary ammonium moiety

Abstract

Polydiallyldimethylammonium chloride (PDDA, cationic polymer containing quaternary ammonium ions) incorporated hydroxyapatites (PDDA-HAPs) are prepared via a one-pot hydrothermal method. XRD analysis shows that diffraction patterns of PDDA-HAP are almost identical to those of pure HAP. Line broadening of diffraction patterns is observed in PDDA-HAP compared to pure HAP. The morphology of pure HAP and PDDAHAP shows round tip-elongated rod. 43 nm length of pure HAP is reduced by approximately 18 % to 35 nm of PDDA-HAP. Surface elemental analysis (XPS) confirms that atomic percentage of nitrogen gradually increases from 0.36 to 1.02 as the amount of PDDA increases. This nitrogen atomic percentage of the quaternary ammonium moiety directly correlates with increased surface charge (zeta potential) from near-neutral values (+0.401 mV) for pure HAP to +33 mV for PDDA- HAP. While pure HAP exhibits immediate precipitation in aqueous solution, PDDA-HAP remains colloidal stability for up to five days, making it a promising material for biomedical applications requiring stable suspensions.