Microwave irradiated click reactions on silicon surfaces via derivertization of covalently grafted poly(PEGMA) brushes

Two surface chemistry approaches were realized to complete click reactions at covalently grafted polymer brushes of poly(poly(ethylene glycol) monomethacrylate) on a planar silicon surface (Si-g-P(PEGMAOH)). On one hand, the hydroxyls from Si-g-P(PEGMAOH) brushes can be replaced by chlorines of thionyl chloride and then chlorines can be substituted with azides of sodium azide to achieve azide-terminated (Si-g-P(PEGMAN3)) brushes. On the other hand, the terminal acetylene (Si-g-P(PEGMACH2CCH)) brushes can be prepared easily by reaction between Si-g-P(PEGMAOH) and propargyl bromide. Model compounds of acetylene-terminated propargylamine, propiolic acid, and 10-undecynoic acid as well as azide-terminal benzyl azide were chosen to investigate the surface click reactions catalyzed with Cu(II)/sodium L-ascorbate by microwave irradiation under very mild conditions at 30 °C for 1 h. The stepwise modifications were characterized by two surface-sensitive techniques, Multiple Transmission-Reflection Infrared Spectroscopy (MTR-IR) and X-ray Photoelectron Spectroscopy (XPS), and their spectra were analyzed in detail. The triazole ring v(HC) stretching at 3139 cm−1 and the XPS high-resolution scan of N 1s directly confirm the click reactions. By quantifying their infrared spectra before and after click reactions, we conclude that the click reactions on silicon surfaces by microwave irradiation possess high yield and efficiency. Hence, the microwave irradiated click reaction approaches might open convenient avenues to fabricate functional and hybrid organic/silicon devices.

Graphical abstractPoly(poly(ethylene glycol) monomethacrylate) brushes grafted from a planar silicon hydride surface were converted to azide-/acetylene-terminated brushes. Then surface click reactions were executed by microwave irradiation under extremely mild conditions.Figure optionsDownload full-size imageDownload high-quality image (40 K)Download as PowerPoint slideHighlights► Click reactions were executed on polymer brushes via silicon surface induced ATRP. ► Microwave irradiation assisted surface click reactions at 30 °C for 1 h. ► MTR-IR Spectroscopy reveals tiny details of click reactions. ► Microwave-assisted surface reactions could have broad application.