Polymer brushes grafted to Passivated silicon substrates using click chemistry

We present herein a versatile method for grafting polymer brushes to passivated silicon surfaces based on the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (click chemistry) of w-azido polymers and alkynyl-functionalized silicon substrates. First, the passivation of the silicon substrates toward polymer adsorption was performed by the deposition of an alkyne functionalized self-assembled monolayer (SAM). Then, three tailormade w-azido linear brush precursors, i.e., PEG-N-3, PMMA-N-3, and PS-N-3 (M-n similar to 20 000 g/mol), were grafted to alkyne-functionalized SAMs via click chemistry in tetrahydrofuran. The SAM, PEG, PMMA, and PS layers were characterized by ellipsometry, scanning probe microscopy, and water contact angle measurements. Results have shown that the grafting process follows the scaling laws developed for polymer brushes, with a significant dependence over the weight fraction of polymer in the grafting solution and the grafting time. The chemical nature of the brushes has only a weak influence on the click chemistry grafting reaction and morphologies observed, yielding polymer brushes with thickness of ca. 6 nut and grafting densities of ca. 0.2 chains/nm(2). The examples developed herein have shown that this highly versatile and tunable approach can be extended to the grafting of a wide range of polymer (pseudo-) brushes to silicon substrates without changing the-tethering strategy.