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Thermally Activated One-Pot, Simultaneous Radical and Condensation Reactions Generate Surface-Anchored Network Layers from Common Polymers

Pandiyarajan, C. K., Genzer, Jan
Macromolecules 2019 v.52 no.2 pp. 700-707
annealing, azides, chemical bonding, condensation reactions, crosslinking, gels, heat, nitrogen, polymers, protons, synthesis, temperature
We present a versatile one-pot synthesis method that generates surface-attached polymer networks by cross-linking common polymers using thermally 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). Upon heating, 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 cross-linked polymer to the substrate. We carry out 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 the polymer network and anchors the network to various substrates.