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

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