Effect of Micellization pH on Properties of Sphere-like Mesoporous Hydroxyappatite

Mesoporous hydroxyapatites were syntesized by self-assembly method using Cetyltrimethylammonium bromide (CTAB) as cationic surfactant and 1-dodecanethiol as pore expander with pore expander/surfactant mass ratio of 4.22 and synthesis temperature of 80 °C at different micellization pH values. The field emission-scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, pore size distribution plot (Barrettt, Joyner, and Halenda (BJH) method), fourier transform infrared spectroscopy (FTIR) and low-angle X-ray diffraction (LA-XRD) results beside the titration investigation of 1-dodecanethiol revealed that ionizied 1-dodecanethiol concentration ([RS-]) increased exponentially by changes in pH. The micellization pH has a key role in physico-chemical characteristics of samples. Increase in pH can change the ionization degree of 1-didecanethiol and swell the micelle and also lead to larger pores (pore diameter of 2.93 in lower pH and 24.48 in higher pH). Changes in the micellization pH also affect the dielectric constant of water and lead to variation in patricle size.