Abstract
Silicones are usually considered to be inert and, thus, not reactive with surfaces. Here we show that the most common silicone, methyl-terminated polydimethylsiloxane, spontaneously and stably bonds on glass—and any other material with silicon oxide surface chemistry—even at room temperature. As a result, a 2–5 nm thick and transparent coating, which shows extraordinary nonstick properties toward polar and nonpolar liquids, ice, and even super glue, is formed. Ten microliter drops of various liquids slide off a coated glass when the sample is inclined by less than 10°. Ice adhesion strength on a coated glass is only 2.7 ± 0.6 kPa, that is, more than 98% less than ice adhesion on an uncoated glass. The mechanically stable coating can be easily applied by painting, spraying, or roll-coating. Notably, the reaction does not require any excess energy or solvents, nor does it induce hazardous byproducts, which makes it an ideal option for environmentally sustainable surface modification in a myriad of technological applications.
Highlights
Silicones are colorless, nontoxic, and generally considered to be biocompatible materials
Linear PDMS with molecular weights (MW) of 770 and 49 350 g mol−1 was purchased from Gelest, Inc., and PDMS of MW 2000, 6000, 14 000, 28 000, 63 000, and 117 000 g mol−1 were from Alfa Aesar
Careful rinsing with solvents, for example, with toluene, which is a good solvent for PDMS, does not remove all the excess, unbound PDMS
Summary
Nontoxic, and generally considered to be biocompatible materials. The most common silicone is trimethylsiloxy terminated linear poly(dimethylsiloxane) (PDMS). It has an inorganic silicon (Si)−oxygen (O) backbone with two organic methyl side groups (−CH3) attached to each silicon atom (Supporting Information, Figure S1).[1] The organic/inorganic molecular structure gives PDMS its unique properties. The low electronegativity of Si leads to highly polarized Si−O bonds in PDMS backbone (Supporting Information, Table S1). The large bond energy of 452 kJ mol−1 gives PDMS its high thermal stability.[1] The hydrophobic methyl side groups provide low surface energy and shield the inorganic Si−O backbone, thereby lowering intermolecular interactions within PDMS. Because of its low surface tension γ ≈ 20 mN m−1 PDMS wets most materials.[1] The wide bond angle of
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