Wettability Reversal of Hydrophobic Pigment Particles Comprising Nanoscale Organosilane Shells: Concentrated Aqueous Dispersions and Corrosion-Resistant Waterborne Coatings.

We demonstrate the synthesis of polysiloxane-modified inorganic-oxide nanoparticles comprising a TiO-based pigment (Ti-Pure R-706), which undergo drastic wettability reversal from a hydrophilic wet state to a hydrophobic state upon drying. Furthermore, the dry hydrophobic pigment particles can be reversibly converted back to a hydrophilic form by the application of high shear aqueous milling. Our synthetic approach involves first condensing the cross-linking monomer CHSi(OH) onto the surface of Ti-Pure R-706 at pH 9.

Stable Aqueous Dispersions of Hydrophobically Modified Titanium Dioxide Pigments through Polyanion Adsorption: Synthesis, Characterization, and Application in Coatings.

Polyanion dispersants stabilize aqueous dispersions of hydrophilic (native) inorganic oxide particles, including pigments currently used in paints, which are used at an annual scale of 3 million metric tons. While obtaining stable aqueous dispersions of hydrophobically modified particles has been desired for the promise of improved film performance and water barrier properties, it has until now required either prohibitively complex polyanions, which represent a departure from conventional dispersants, or multistep syntheses based on hybrid-material constructs. Here, we demonstrate the aqueous dispersion of alkylsilane-capped inorganic oxide pigments with conventional polycarboxylate dispersants, such as carboxymethylcellulose (CMC) and polyacrylate, as well as a commercial anionic copolymer.

Effects of freezing and thawing on the microstructure of latex paints.

Freeze-thaw (FT) cycles can aggregate particles in aqueous paint suspensions. To understand the mechanism of particle aggregation, cryogenic scanning electron microscopy (cryoSEM) was used to visualize the microstructure after the freezing and thawing steps of the FT cycle. After the freezing step, cryoSEM images show that the microstructure contains ice crystals and particle-rich regions.

Spatially resolved solid-state 1H NMR for evaluation of gradient-composition polymeric libraries.

Polyurethane libraries consisting of films with composition gradients of aliphatic polyisocyanate and hydroxy-terminated polyacrylate resin were characterized using methods of (1)H NMR microimaging (i.e., magnetic resonance imaging, (MRI)) and solid-state NMR.