(420g) One-Pot Synthesis of Surface-Anchored Gradient Networks from Common Polymers

We present a versatile one-pot synthesis method that generates surface-attached gradient polymer networks by crosslinking common polymers using thermally- and UV-active 6-azidosulfonylhexyltriethoxysilane (6-ASHTES), which acts as a cross-linker and a surface-anchoring agent. We deposit a thin layer (∼200 nm) of a mixture comprising a given amount of 6-ASHTES and a polymer onto the substrate and anneal it at elevated temperatures (100−140°C) and/or UV-irradiated at 254 nm (4-10 J/cm²). Upon heating or UV-irradiation, the sulfonyl azide groups release nitrogen, and the resulting nitrenes abstract protons from the neighboring C−H bonds in polymers and undergo a C−H insertion reaction and/or recombination to form sulfonamide bonds. Condensation among ethoxysilane headgroups in bulk links 6-ASHTES units completes cross-linking. Simultaneously, 6-ASHTES reacts with substrate-bound −OH or C−H groups and attaches the covalently crosslinked polymer to the substrate. Such as a versatile system allows complete control over the gel fraction in orthogonal directions by spatially and orthogonally controlling UV dose and/or temperature. We carry out a systematic investigation of gel kinetics involving annealing temperature, annealing time, and the concentration of 6-ASHTES for various polymer systems. This simple yet versatile approach involving simultaneous radical and condensation reactions adjusts the gel fraction in gradient fashion and anchors the polymer network to various substrates.