Rapid and Efficient Collection of Platinum from Karstedt’s Catalyst Solution via Ligands-Exchange-Induced Assembly

Reported herein is a novel strategy for the rapid and efficient collection of platinum from Karstedt’s catalyst solution. By taking advantage of a ligand-exchange reaction between alkynols and the 1,3-divinyltetramethyldisiloxane ligand (M^ViM^Vi) that coordinated with platinum (Pt(0)), the Karstedt’s catalyst particles with a size of approximately 2.5 ± 0.7 nm could be reconstructed and assembled into larger particles with a size of 150 ± 35 nm due to the hydrogen bonding between the hydroxyl groups of the alkynol. In addition, because the silicone-soluble M^ViM^Vi ligand of the Karstedt’s catalyst was replaced by water-soluble alkynol ligands, the resultant large particles were readily dispersed in water, resulting in rapid, efficient, and complete collection of platinum from the Karstedt’s catalyst solutions with platinum concentrations in the range from ∼20 000 to 0.05 ppm. Our current strategy not only was used for the rapid and efficient collection of platinum from the Karstedt’s catalyst solutions, but it also enabled the precise evaluation of the platinum content in the Karstedt’s catalysts, even if this platinum content was extremely low (i.e., 0.05 ppm). Moreover, these platinum specimens that were efficiently collected from the Karstedt’s catalyst solutions could be directly used for the evaluation of platinum without the need for pretreatment processes, such as calcination and digestion with hydrofluoric acid, that were traditionally used prior to testing via inductively coupled plasma mass spectrometry in conventional methods

Robust Superamphiphobic Coatings Based on Silica Particles Bearing Bifunctional Random Copolymers

Reported herein is the growth of bifunctional random copolymer chains from silica particles through a “grafting from” approach and the use of these copolymer-bearing particles to fabricate superamphiphobic coatings. The silica particles had a diameter of 90 ± 7 nm and were prepared through a modified Stöber process before atom transfer radical polymerization (ATRP) initiators were introduced onto their surfaces. Bifunctional copolymer chains bearing low-surface-free-energy fluorinated units and sol–gel-forming units were then grafted from these silica particles by surface-initiated ATRP. Perfluorooctyl ethyl acrylate (FOEA) and 3-(triisopropyloxy)­silylpropyl methacrylate (IPSMA) were respectively used as fluorinated and sol–gel-forming monomers in this reaction. Hydrolyzing the IPSMA units in the presence of an acid catalyst yielded silica particles that were adorned with silanol-bearing copolymer chains. Coatings were prepared by spraying these hydrolyzed silica particles onto glass and cotton substrates. A series of four different copolymer-functionalized silica particles samples bearing copolymers with similar FOEA molar fractions (<i>f</i>_F) of ∼80% but with different copolymer grafting mass ratios (<i>g</i>_m) that ranged between 12.3 wt % and 58.8 wt %, relative to silica, were prepared by varying the polymerization protocols. These copolymer-bearing silica particles with a <i>g</i>_m exceeding 34.1 wt % were used to coat glass and cotton substrates, yielding superamphiphobic surfaces. More importantly, these particulate-based coatings were robust and resistant to solvent extraction and NaOH etching thanks to the self-cross-linking of the copolymer chains and their covalent attachment to the substrates

Synthesis and Bulk Self-Assembly of Well-Defined Binary Graft Copolymers

Six binary graft copolymers were synthesized, and their graft segregation in bulk was investigated. The copolymers were prepared by a one-pot method involving the quantitative grafting of alkyne-end-functionalized poly­(<i>n</i>-butyl acrylate) (PBA-CCH) and poly­(2-cinnamoyloxyethyl methacrylate) (PCEMA-CCH) onto poly­(3-azide-2-hydroxypropyl methacrylate) (P­(GMA-N₃)) via click chemistry. Of these copolymers, three had a total PBA and PCEMA molar grafting density <i>g</i> of ∼20%, and their PBA volume fractions <i>V</i>_B among PBA and PCEMA varied between 28% and 57%. <i>V</i>_B was constant at ∼57%, while <i>g</i> varied between 9.8% and 29.5% for the other three samples. Bulk films were obtained by slowly evaporating the solvent from cast solutions of these copolymers. These films were then annealed above the glass transition temperatures of PBA and PCEMA to facilitate graft segregation. The graft segregation patterns were examined by performing transmission electron microscopy (TEM) analysis of thin sections of these films. The TEM results suggested that the grafted PBA chains formed a disordered wormlike phase in a PCEMA matrix at <i>V</i>_B = 28%. At <i>V</i>_B = 42% and 57%, PBA and PCEMA seemed to form alternating lamellae. In the former case, the PBA layers were thinner than the PCEMA layers, while the PBA layers were thinner in the latter case. All three samples with <i>V</i>_B ∼ 57% probably possessed a lamellar morphology. The periodicity of the lamellae increased and the long-range ordering deteriorated as <i>g</i> increased

Superparamagnetic-Oil-Filled Nanocapsules of a Ternary Graft Copolymer

Stearic and oleic acid-coated Fe₃O₄ nanoparticles were dispersed in decahydronaphthalene (DN). This oil phase was dispersed in water using ternary graft copolymer poly­(glycidyl methacrylate)-<i>graft</i>-[polystyrene-<i>ran</i>-(methoxy polyethylene glycol)-<i>ran</i>-poly­(2-cinnamoyloxyethyl methacrylate)] or PGMA-<i>g</i>-(PS-<i>r</i>-MPEG-<i>r</i>-PCEMA) to yield capsules. The walls of these capsules were composed of PCEMA chains that were soluble in neither water nor DN, and the DN-soluble PS chains stretched into the droplet phase and the water-soluble MPEG chains extended into the aqueous phase. Structurally stable capsules were prepared by photolyzing the capsules with UV light to cross-link the PCEMA layer. Both the magnetite particles and the magnetite-containing capsules were superparamagnetic. The sizes of the capsules increased as they were loaded with more magnetite nanoparticles, reaching a maximal loading of ∼0.5 mg of ligated magnetite nanoparticles per mg of copolymer. But the radii of the capsules were always <100 nm. Thus, a novel nanomaterialsuperparamagnetic-oil-filled polymer nanocapsuleswas prepared. The more heavily loaded capsules were readily captured by a magnet and could be redispersed via shaking. Although the cross-linked capsules survived this capturing and redispersing treatment many times, the un-cross-linked capsules ruptured after four cycles. These results suggest the potential to tailor-make capsules with tunable wall stability for magnetically controlled release applications

Superhydrophobic Hierarchically Assembled Films of Diblock Copolymer Hollow Nanospheres and Nanotubes

Reported are the formation of rough particulate films from cross-linked diblock copolymer vesicles and nanotubes and the wetting properties of the resultant films. The diblock copolymers used were F₆₆M₂₀₀ and F₉₅A₁₃₅, where the subscripts denote the repeat unit numbers, whereas M, A, and F denote poly­(2-cinnamoyloxyethyl methacrylate), poly­(2-cinnamoyloxyethyl acrylate), and poly­(2,2,2-trifluoroethyl methacrylate), respectively. The precursory polymers to F₆₆M₂₀₀ and F₉₅A₁₃₅ were prepared by atom transfer radical polymerization. In 2,2,2-trifluoroethyl methacrylate (FEMA), a selective solvent for F, vesicles and tubular micelles were prepared from F₆₆M₂₀₀ and F₉₅A₁₃₅, respectively. Photo-cross-linking the M and A blocks of these aggregates yielded hollow nanospheres and nanotubes bearing F coronal chains. These particles were dispersed into CH₂Cl₂/methanol, where CH₂Cl₂ was a good solvent for both blocks and methanol was a poor solvent for F. Casting CH₂Cl₂/methanol dispersions of these particles yielded films consisting of hierarchically assembled diblock copolymer nanoparticles. For example, the hollow nanospheres fused into microspheres bearing nanobumps after being cast from CH₂Cl₂/methanol at methanol volume fractions of 30 and 50%. The roughness of these films increased as the methanol volume fraction increased. The films that were cast at high methanol contents were superhydrophobic, possessing water contact angles of ∼160° and water sliding angles of ∼3°