Surface Modification of Poly(divinylbenzene) Microspheres via Thiol−Ene Chemistry and Alkyne−Azide Click Reactions

We report the functionalization of cross-linked poly(divinylbenzene) (pDVB) microspheres using both thiol−ene chemistry and azide−alkyne click reactions. The RAFT technique was carried out to synthesize SH-functionalized poly(N-isopropylacrylamide) (pNIPAAm) and utilized to generate pNIPAAm surface-modified microspheres via thiol−ene modification. The accessible double bonds on the surface of the microspheres allow the direct coupling with thiol-end functionalized pNIPAAm. In a second approach, pDVB microspheres were grafted with poly(2-hydroxyethyl methacrylate) (pHEMA). For this purpose, the residual double bonds on the microspheres surface were used to attach azide groups via the thiol−ene approach of 1-azido-undecane-11-thiol. In a second step, alkyne endfunctionalized pHEMA was used to graft pHEMA to the azide-modified surface via click-chemistry (Huisgen 1,3-dipolar cycloaddition). The surface-sensitive characterization methods X-ray photoelectron spectroscopy, scanning-electron microscopy and FT-IR transmission spectroscopy were employed to characterize the successful surface modification of the microspheres. In addition, fluorescence microscopy confirms the presence of grafted pHEMA chains after labeling with Rhodamine B.