Chemically Modified Hydroxyapatite Nanocrystals by Temperature-Responsive Poly(N-isopropylacrylamide) via Surface Initiated Radical Polymerization

Abstract

This article reports on application of surface-initiated thiol-lactam initiated radical polymerization (TLIRP) method to modify hydroxyapatite nanocrystals (HAP) with thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) brushes through grafting from strategy. Initially, 3-mercaptopropyl trimethoxysilane possessing thiol groups was functionalized with the -OH species on the surface of hydroxyapatite through ligand-exchanging response to introduce thiol species on hydroxyapatite (hydroxyapatite-thiol). Subsequently, attaching polymerization of N-isopropylacrylamide from HAP-SH surface was accomplished in the attendance of butyrolactam to produce PNIPAAmg-HAP. Thermogravimetric analysis, Fourier transform infrared, X-ray photoelectron spectroscopy and their thermal phase transition behaviour were employed to confirm the grafting and to characterize the nanoparticle structure.