Surface engineering of Si wafers with tunable surface morphology and stiffness via visible light induced thiol‐ene click polymerization with 4‐(N,N‐diphenylamino)benzaldehyde as an organocatalyst

Abstract

AbstractA facile strategy is developed to fabricate a two‐layer grafted polymer coatings on silicon wafers, specifically soft crosslinked polythioether as middle damping layer and stiff poly(methyl methacrylate) (PMMA) as top protecting layer. At first, a highly crosslinked polythioether layer was constructed on the surface of the silicon wafer with tunable thickness and smooth morphology with trimethylolpropane tris(2‐mercaptoacetate) and pentaerythritol triallyl ether as monomers and 4‐(N,N‐diphenyl‐amino)benzaldehyde as an organocatalyst. The Young's modulus of the grafted crosslinked polythioether layer is about 300–400 MPa and the roughness is about 11.3 nm measured by atomic force microscope. There are about 9000 ea reactive –SH in a cuboid cell with 1 nm2 base area and 7–14 μm height in the grafted crosslinked polythiolether layer. Then, a flatten PMMA coating layer with Young's modulus as high as ~2.4 GPa was grafted from/onto the surface of the crosslinked polythiolether with surface –SH groups as initiating or chain transfer sites.