A comparative study of apatite deposition on polyamide films containing different functional groups under a biomimetic condition

This work compares the induction period for the nucleation of apatite, rate of crystal growth, and adhesive strength of apatite formed on polyamide films containing either carboxyl or sulfonic groups incorporated with calcium chloride by immersing them in 1.5SBF, whose ion concentrations are 1.5 times those of a simulated body fluid (SBF). The induction period for apatite nucleation on polyamide containing-SO₃H was shorter than for polyamide containing-COOH, while the rate of crystal growth did not depend on the kind of functional group, but depended on the degree of supersaturation of the surrounding solution. The more ready association of sulfonic groups with calcium ions may lead to a shorter induction period for apatite nuclei than that with carboxyl groups. Adhesive strength of apatite layer with polyamide film containing - SO₃H was significantly lower than that with - COOH depending not only on the chemical interactions but also on the mechanical properties of the polyamide film.