Structure and stability analysis of biocompatible hydroxyapatite reinforced chitosan nanocomposite

Nano-hydroxyapatite has been used in multifunctional potential clinical applications where certain particle size distribution and morphology are required. The hydroxyapatite/chitosan composites were prepared using in situ co-precipitation technique, influence of the reaction temperature on the crystallization and particle growth of the synthesized nano-hydroxyapatite were examined. It was observed that the increase in synthesis temperature had a great influence on particle size and crystal structure of nano-hydroxyapatite, whereas, the low temperature showed inhabitation of the hydroxyapatite growth in c-direction and low crystallinity which was confirmed using XRD and electron diffraction pattern of TEM micrographs. The molar ratio of the bone-like apatite layer for composite prepared at 70 degrees C was higher was higher than the composites prepared at lower temperatures (40 degrees C and -5 degrees C). The AFM images of -5 degrees C, 40 degrees C, and 70 degrees C n-HAp/CTS composite display presence of CTS rich domains. These CTS rich and domains are made of smaller globular shaped particles in which, n-HAp particles are embedded in the polymer matrix. The SBF degraded AFM surface topography of the composites shows the CTS is degraded fast rather the n-HAp. The elastic modulus determined from nanoindentation of -5 degrees C, 40 degrees C, and 70 degrees C n-HAp/CTS composites are 17.91, 24.56, and 30.62 GPa respectively. Hardness values of the three composites in the same order were found to be 0.86, 1.35, and 1.74 GPa, respectively. Macro-mechanical tests showed significant enhancement in elastic modulus, coefficient of friction and hardness of 70 degrees C n-HAp/CTS composites over -5 degrees C and 40 degrees C n-HAp/CTS. However, the SBF degraded samples also performed moderate improvement in nanomechanical property. POLYM. COMPOS., 39:E573-E583, 2018. (c) 2018 Society of Plastics Engineers