Tuning Oleophobicity of Silicon Oxide Surfaces with Mixed Monolayers of Aliphatic and Fluorinated Alcohols

Abstract

We demonstrate the formation of mixed monolayers derived from a microwave-assisted reaction of alcohols with silicon oxide surfaces in order to tune their surface oleophobicity. This simple, rapid method provides an opportunity to precisely tune the constituents of the monolayers. As a demonstration, we sought fluorinated alcohols and aliphatic alcohols as reagents to form monolayers from two distinct constituents for tuning the surface oleophobicity. The first aspect of this study sought to identify a fluorinated alcohol that formed monolayers with a relatively high surface coverage. It was determined that 1H,1H,2H,2H-perfluoro-1-octanol yielded high quality monolayers with a water contact angle (WCA) value of ∼110° and contact angle values of ∼80° with toluene and hexadecane exhibiting both an excellent hydrophobicity and oleophobicity. Tuning of the oleophobicity of the modified silicon oxide surfaces was achieved by controlling the molar ratio of 1H,1H,2H,2H-perfluoro-1-octanol within the reaction mixtures. Surface oleophobicity progressively decreased with a decrease in the fluorinated alcohol content while the monolayers maintained their hydrophobicity with WCA values of ∼110°. The simple and reliable approach to preparing monolayers of a tuned composition that is described in this article can be utilized to control the fluorocarbon content of the hydrophobic monolayers on silicon oxide surfaces.

Covalent Surface Modification of Silicon Oxides with Alcohols in Polar Aprotic Solvents

“…These peaks agree with the previously reported peak positions for these respective species based on the high resolution C1s XPS of fluorinated monolayers. 37,39,[46][47][48] Monolayers derived from either glycolic acid or 5hydroxypentanal contained three distinct peaks in their high resolution C1s XPS analyses. For the substrate reacted with glycolic acid, the peaks attributed to C−C, C−O, and C=O were located at binding energies of 285.3 eV, 287.1 eV, and 289.4 eV, respectively.…”

“…[35][36][37][38] Both hydrogen-terminated silicon and hydroxyl-terminated silicon oxide surfaces have been functionalized with alcohol reagents using reactions initiated by convective heating, 35 UV radiation, 36 or microwave heating. 37,39 These reports relied on reactions carried out at relatively high temperatures in mostly neat solutions. While these approaches provide a simple reaction strategy for the formation of monolayers, it can limit the choice alcohols available for the reaction due to possible thermal degradation or other side reactions at high temperatures.…”

“…Moreover, neat solutions will have fundamental implications on the reaction kinetics and the formation of multicomponent monolayers. [39][40][41][42] It is desirable to identify a solvent to facilitate the formation of alcohol based monolayers for a versatile tuning of the surface chemistry of silicon oxides.…”

Tuning the Surface Chemistry of Second-Harmonic-Active Lithium Niobate Nanoprobes Using a Silanol–Alcohol Condensation Reaction

“…34,41−45 The attachment of alcohol-containing reagents to materials through the silanol− alcohol condensation reaction can provide a facile means of preparing −COOH-terminated surfaces. This reaction has been applied to planar surfaces (e.g., silica, borosilicate glasses), 36,37 but its application to NPs requires further investigation. Extending these reactions to the surface modification of nanoscale optical contrast agents (e.g., SHGactive nanoscale probes) provides an opportunity to both tune the properties of these nanoprobes and demonstrate an alternative approach to functionalizing the surfaces of these and other NPs.…”

Determining the thickness of aliphatic alcohol monolayers covalently attached to silicon oxide surfaces using angle-resolved X-ray photoelectron spectroscopy

“…The alcohol molecules can form silyl ether bonds with either hydrogen terminated silicon [25][26][27][28][29][30] or silicon oxides (i.e. silanol terminated surfaces) [31][32][33][34]. Minimal side reactions for these processes enable a convenient approach to prepare uniform monolayers, which includes the use of ambient environmental conditions.…”