Vi‐PDMS incorporated with protein‐based coatings designed for permeability‐enhanced applications

Functional polydimethylsiloxanes containing vinyl groups (Vi‐PDMS) were used for silicone‐based organic polymers in composites and adhesive formulations. Poly(butyl acrylate/methyl methacrylate/vinyl silicone oil)/casein–caprolactam [P(BA‐MMA‐Vi‐PDMS)/CA‐CPL] nanoparticles were prepared via emulsifier‐free polymerization. The well‐defined core–shell structure of P(BA‐MMA‐Vi‐PDMS)/CA‐CPL nanoparticles was verified by transmission electron microscopy. The results of scanning electron microscopy and contact angle measurements proved that the as‐obtained coatings exhibited porous and hydrophobic properties, which were helpful for superior water vapor permeability. By comparing the appearance of the coatings before and after adhesion analysis, the excellent adhesion strength was proved to be dominated by Vi‐PDMS. The relationship between interface morphology and properties of the resultant coatings was investigated in detail. The nucleation mechanism for this soap‐free emulsion synthesis was also proposed accordingly. These results could help in designing coatings with better surface properties and wider application. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46501.     

Assembly and Transport of Microscopic Cargos via Reconfigurable Photoactivated Magnetic Microdockers

The realization of micromotors able to dock and transport microscopic objects in a fluid medium has direct applications toward the delivery of drugs and chemicals in small channels and pores, and the realization of functional wireless microrobots in lab‐on‐a‐chip technology. A simple and general method to tow microscopic particles in water by using remotely controllable light‐activated hematite microdockers is demonstrated. These anisotropic ferromagnetic particles can be synthesized in bulk and present the remarkable ability to be activated by light while independently manipulated via external fields. The photoactivation process induces a phoretic flow capable to attract cargos toward the surface of the propellers, while a rotating magnetic field is used to transport the composite particles to any location of the experimental platform. The method allows the assembling of small colloidal clusters of various sizes, composed by a skeleton of mobile magnetic dockers, which cooperatively keep, transport, and release the microscopic cargos. The possibility to easily reconfigure in situ the location of the docker above the cargo is demonstrated, which enables optimize transport and cargo release operations.     

Selectivity of Hydrophilic and Hydrophobic TiO2 for Organic‐Based Dispersants

The effects of the surface chemistry of TiO₂ powders on the dispersion performance of various dispersants are studied. Four common dispersants (oleic acid, oleylamine, oleyl phosphate, and tris‐(2‐butoxyethyl) phosphate) with different functional groups (carboxyl (–COOH), amino (–NH₂), phosphate (–P(=O)(OH)₂), and –P(=O)) are investigated for their potential to disperse hydrophilic and hydrophobic titania (TiO₂) powders. The outcomes, based on adsorption kinetics, adsorption isotherms, rheologies, and theoretical calculations, indicate that the hydrophilic TiO₂ is more sensitive to the chemistry of dispersants as compared to the hydrophobic TiO₂. However, the relative dispersion efficiencies of the dispersants are not found relevant to the adsorption kinetics, which is dominated by the adsorption amount. In addition, hydrogen bonding between –OH groups of the phosphate‐based dispersants dominates their dispersion ability for TiO₂.     

Influence of Sophorolipid Structure on Interfacial Properties of Aqueous-Arabian Light Crude and Related Constituent Emulsions

Sophorolipids (SLs) offer an “environmentally friendly” alternative to chemically produced surfactants currently used in formulations for crude oil extraction, processing, and reclamation. Studies herein describe how sophorolipid structure influences its interfacial properties for environmentally and industrially relevant oil–water systems where the oil phase is Arabian light crude oil, paraffin oil, decane, hexadecane, a 1:1 vol/vol mixture of o-xylene and 1,2-dimethylcyclohexane, or a mixture of paraffin oil, o-xylene, and 1,2-dimethylcyclohexane (synthetic crude oil). SL-hexyl ester (SL-HE) reduces the crude oil–water interfacial tension (IFT) by 57 and 91% at 0.001 and 0.5 mg/mL, respectively. Crude oil displacement tests reveal that SL-ethyl ester (SL-EE) and SL-HE contract a crude oil slick on water to about 20% of its starting volume allowing for easier burning of spilled crude oil on marine surfaces. Water retention and emulsion phase (e.g., o/w vs. w/o) are determined by SL-structure/concentration, oil concentration, and oil composition to understand their performance for crude oil transportation and clean-up. For the first time, w/o emulsions were obtained using SLs and their formation occurred after homogenization when the oil phase consisted of a 1:1 mixture of o-xylene and 1,2-dimethylcyclohexane. Generally, the performance of SL-esters in the above studies was superior to that using Triton X-100, a comparison nonionic surfactant. Hence, SL-esters offer a valuable platform for tuning interfacial properties to optimize surfactant performance.     

Dye‐containing nonaqueous dispersions derived from methanol‐soluble polymers stabilized by block–random copolymer surfactant

In this study, nonaqueous emulsion solvent evaporation was utilized to prepare nonaqueous dispersions derived from various methanol‐soluble polymers, such as polyvinylpyrrolidone (PVP), polyethylene glycol, polyvinyl acetate (PVAC), and poly(acrylic acid), using a block–random copolymer surfactant; the block–random copolymer poly(SMA)₈₈‐b‐poly(DEAGMA₁₅‐r‐SMA₁₄), composed of stearyl methacrylate, and diethanolamine‐modified glycidyl methacrylate, was used to stabilize the nonaqueous emulsions of methanol containing the polymers and an isoparaffin solvent, Isopar M. In the cases without dye, all emulsions and dispersions obtained after the evaporation of methanol exhibited nanometer‐sized particles as well as good stability. For emulsions consisting of dye‐containing methanol phases, particle sizes and stability of the obtained dispersions were dependent on the nature of the methanol‐soluble polymers. The dispersions derived from PVP and PVAC, which possibly interact weakly with the block–random copolymer and dye, exhibited good stability and a small particle size, which can be applied for inkjet printing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44671.     

PtRu Colloid Nanoparticles for CO Oxidation in Microfabricated Reactors

The catalytic activity of PtRu colloid nanoparticles for CO oxidation is investigated in microfabricated reactors. The measured catalytic performance describes a volcano curve as a function of the Pt/Ru ratio. The apparent activation energies for the different alloy catalysts are between 21 and 117 kJ/mol, which agree well with literature. The size distribution of the colloid nanoparticles is determined from STM and TEM, from which an average size of the colloid nanoparticles of 2.2±0.5 nm is determined.     

Structural characterization of oligomers from the polycondensation of citric acid with ethylene glycol and long‐chain aliphatic alcohols

The structural characterization of polyesters of citric acid (CA) with ethylene glycol and long‐chain aliphatic alcohols (ROH), prepared by the composition of the reaction mixture being adjusted slightly away from stoichiometric equivalence, was performed with ¹H‐ and ¹³C‐NMR spectroscopy. The aliphatic alcohols employed were 1‐decanol, 1‐dodecanol, and 1‐octadecanol. The ¹³C‐NMR carbonyl region presented four groups of signals, two corresponding to the ester groups and two corresponding to the acid groups. However, symmetric and asymmetric groups of CA moieties were identified in the ¹³C‐NMR spectra. The ester yield from ROH decreased as the number of carbon atoms in the alcohols increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 302–306, 2003     

Associative polymer/latex dispersion phase diagrams II: HASE thickeners

The colloidal interactions of HASE associative polymers and latexes in the presence of surfactant are complicated and subject to a number of variables. Both bridging and depletion flocculation can occur, in addition to good particle dispersion. Dispersion phase diagrams have been developed to help visualize these interactions. The various dispersion states can have a significant effect on coating formulations and film properties. Examples of dispersion phase diagrams are presented for a model HASE anionic associative thickener and various model latexes in the presence of sodium dodecyl-sulfate and nonionic surfactants. The major variables affecting dispersion behavior are associative polymer concentration, latex particle size, latex surface hydrophobicity, electrolyte concentration, and surfactant concentration. The dispersion phase behavior of the HASE systems is compared to that of HEUR thickened systems reported previously. A significant difference is that much less bridging flocculation is observed in the HASE systems. In addition, nonionic surfactants induced depletion flocculation in the HASE systems but not in the HEUR systems.