Hydrophobization of Inorganic Oxide Surfaces via Ring-Opening Polymerization of Cyclic Siloxane Vapor.

The ability to control the surface chemistry of inorganic oxides has a profound impact on numerous applications, including lubrication, antifouling, and anticorrosion. While often overlooked as potential modifying agents given their lack of traditional functional groups, siloxanes have recently been shown to react readily with and covalently attach to inorganic oxide surfaces. Herein, we examine the reactions of cyclic siloxane vapor with solid interfaces via a ring-opening polymerization (ROP) initiated by the inherent acid/base characteristics of several smooth inorganic oxide surfaces.

Poly(isobutylene) nanoparticles via cationic polymerization in nonaqueous emulsions.

The preparation of poly(isobutylene) (PIB) nanoparticles via cationic emulsion polymerization is presented. As a requirement, an oil-in-perfluoroalkane nonaqueous emulsion is developed, which is inert under the carbocationic polymerization conditions. To stabilize the dichloromethane/hexane droplets in the fluorinated, continuous phase, an amphiphilic block copolymer emulsifier is prepared containing PIB and 1H,1H-perfluoroalkylated poly(pentafluorostyrene) blocks.

Effects of chemical structure on the dynamic and static surface tensions of short-chain, multi-arm nonionic fluorosurfactants.

Fluorinated surfactants with short perfluoroalkyl chains (R(F)) as potential substitutes for the environmentally questionable, long R(F) systems are presented. Three types of nonionic hydrophilic-fluorophilic amphiphiles are synthesized and evaluated based on surface activity in equilibrated (static) and non-equilibrated (dynamic) states. Furthermore, several mono- and disaccharide-based fluorosurfactants are also examined as potential non-bioaccumulative alternatives.

Hydrophobization of inorganic oxide surfaces using dimethylsilanediol.

Dimethylsilanediol is a stable crystalline solid that was described in 1953. As the monomer of an important class of commercial products (poly(dimethylsiloxanes)-silicones, PDMS) and as a simple molecule in its own right (the silicon analog of acetone hydrate), it has been neglected by several fields of fundamental and applied research including the hydrophobization of inorganic oxide surfaces. We report that dimethylsilanediol is a useful reagent for the surface modification (hydrophobization) of oxidized silicon and other oxidized metal surfaces and compare the wetting properties of modified solids with those of conventionally modified surfaces.

Rediscovering silicones: "unreactive" silicones react with inorganic surfaces.

Chemical reactions of linear trimethylsilyl-terminated poly(dimethylsiloxane)s with the surfaces of oxidized silicon, titanium, aluminum, and nickel are reported. These reactions lead to covalently attached poly(dimethylsiloxane) polymer chains and to hydrophobized inorganic surfaces. Linear silicones of this type (silicone oils) are generally not considered to be reactive with inorganic oxide surfaces, and an enormous research effort over the last 50 years to develop other silicon-containing reagents with reactive functional groups did not consider the simple alternative that we report.

Dip-coating crystallization on a superhydrophobic surface: a million mounted crystals in a 1 cm2 array.

Silicon wafers (silicon dioxide surfaces) were patterned by photolithograpy to contain 3 μm (width) × 6 μm (length) × 40 μm (height) staggered rhombus posts in a square array (20 μm center-to-center spacing). These surfaces were hydrophobized using a vapor phase reaction with tridecafluorooctyldimethylchlorosilane and exhibit "superhydrophobicity" (water contact angles of θ(A)/θ(R) = 169°/156°). When a section of a wafer is submerged in and withdrawn from water, the superhydrophobic surface emerges, apparently completely dry.

Contact angle hysteresis on superhydrophobic surfaces: an ionic liquid probe fluid offers mechanistic insight.

Silicon/silicon dioxide surfaces containing 3 μm (width) × 6 μm (length) × 40 μm (height) staggered rhombus posts were prepared using photolithography and hydrophobized using a perfluoroalkyl-containing monofunctional silane. These surfaces exhibit water contact angles of θ(A)/θ(R) = 169°/156°. Water drops come to rest on a carefully aligned horizontal sample but roll when the surface is tilted slightly.

Contact angle hysteresis: a different view and a trivial recipe for low hysteresis hydrophobic surfaces.

Contact angle hysteresis is addressed from two perspectives. The first is an analysis of the events that occur during motion of droplets on superhydrophobic surfaces. Hysteresis is discussed in terms of receding contact line pinning and the tensile failure of capillary bridges.

Displacement reactions of covalently attached organosilicon monolayers on Si.

The covalently attached monolayers of alkylsilanes (R(CH(3))(2)SiX) on Si undergo complete displacement by the solutions of different organosilanes (R'(CH(3))(2)SiX). By varying the reaction time, the degree of displacement can be controlled offering a convenient method for the preparation of surfaces with mixed functionalities (R and R').