Polymer Brushes Grafted to “Passivated” Silicon Substrates Using Click Chemistry

• Published in: Langmuir Vol. 24; no. 6; pp. 2732 - 2739
• Main Authors: Ostaci, Roxana-Viorela, Damiron, Denis, Capponi, Simona, Vignaud, Guillaume, Léger, Liliane, Grohens, Yves, Drockenmuller, Eric
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.03.2008
• Subjects: Catalysis; Chemical Sciences; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Polymers; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water; Self assembly; Monolayer; Catalytic reaction; Acetylenic compound; Hydrocarbon; Scanning probe microscopy; Contact angle; Density; Grafting; Precursor; Ellipsometry; Thickness; Substrate; Scaling law; Chemistry; Adsorption; Morphology; Silicon; Deposition; Silicon polymer; Alkyne; Passivation
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la703086x

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 ω-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 ω-azido linear brush precursors, i.e., PEG−N3, PMMA−N3, and PS−N3 (M n ∼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 nm and grafting densities of ca. 0.2 chains/nm2. 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.