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Tuning the Properties of Surface-Anchored Polymer Networks by Varying the Concentration of a Thermally Activated Cross-Linker, Annealing Time, and Temperature in a One-Pot Reaction

Year: 2021

Journal: ACS Appl. Polym. Mater., Volume 3, NOV 12, page 5568–5577

Authors: Woo, Sun Young; Pandiyarajan, C. K.; Genzer, Jan

Organizations: [NSF DMR-1809453]

Keywords: hydrogel; substrate-anchored network; gel fraction; one-pot reaction; poly(vinylpyrrolidone); sulfonylazide; 6-ASHTES

We investigate the properties of surface-anchored polymer networks created via one-pot synthesis using thermally active 6-azidosulfonylhexyltriethoxysilane (6-ASHTES). 6-ASHTES is a bifunctional gelator that undergoes cross-linking and surface-anchoring reactions when annealed above 100 degrees C. We employ a poly(vinylpyrrolidone) (PVP) with different molecular weights (10-1300 kDa) as a model system to examine the effect of 6-ASHTES concentration, annealing time, and annealing temperature on gel formation. A thin film of PVP/6-ASHTES mixture is deposited on a clean silicon wafer and annealed to form network layers. Spectroscopic ellipsometry measures the film thickness of the cross-linked layers from which the gel fraction and swelling ratio are determined. The gel fraction of PVP in the network can be dialed in by varying the annealing time, temperature, and concentration of 6-ASHTES in the PVP/6-ASHTES mixture. We use a simple Monte Carlo simulation model to describe cross-linking as a function of cross-linker concentration, reaction rate, reaction time, and polymer length. The trends obtained from the model simulations are in qualitative agreement with the experimental data.