Growth-Induced Wrinkles and Dotlike Patterns of a Swollen Fluoroalkylated Thin Film by the Reaction of Surface-Attached Polymethylhydrosiloxane

The design of hydrophobic surfaces requires a material which has a low solid surface tension and a simple fabrication process for anchoring and controlling the surface morphology. A generic method for the spontaneous formation of robust instability patterns is proposed through the hydrosilylation of a fluoroalkene bearing dangling chains, R_f = C₆F₁₃(CH₂)₃-, with a soft polymethylhydrosiloxane (PMHS) spin-coated gel polymer (0.8 μm thick) using Karstedt catalyst. These patterns were easily formed by an irreversible swelling reaction due to the attachment of a layer to various substrates. The buckling instability was created by two different approaches for a gel layer bound to a rigid silicon wafer substrate (A) and to a soft nonswelling silicone elastomer foundation (B). The observations of grafted R_f-PMHS films in the swollen state by microscopy revealed two distinct permanent patterns on various substrates: dotlike of wavelength λ = 0.4-0.7 μm (A) or wrinkle of wavelength λ = 4-7 μm (B). The elastic moduli ratios of film/substrate were determined using PeakForce quantitative nanomechanical mapping. The characteristic wavelengths (λ) of the patterns for systems A and B were quantitatively estimated in relation to the thickness of the top layer. A diversity of wrinkle morphologies can be achieved by grafting different side chains on pristine PMHS films. The water contact angle (WCA) hysteresis of fluorinated chain (R_f) was enhanced upon roughening the surfaces, giving highly hydrophobic surface properties for water with static/hysteresis WCAs of 136°/74° in the resulting wrinkle (B) and 119°/41° in the dotlike of lower roughness (A). The hydrophobic properties of grafted films on A with various mixtures of hexyl/fluoroalkyl chains were characterized by static CA: WCA 104-119°, ethylene glycol CA 80-96°, and n-hexadecane CA 17-61°. A very low surface energy of 15 mN/m for R_f-PMHS was found on the smoother dotlike pattern.

Highly Hydrophobic Cotton Fabrics Modified by Poly(methylhydrogen)siloxane and Fluorinated Olefin: Characterization and Applications

Highly hydrophobic cotton fabrics were obtained with poly(methylhydrogen)siloxane (PMHS) and a further fluorinated olefin modification. The chemical structures and microstructures of PMHS-modified cotton fabrics were characterized, and application of the resultant cotton fabrics in stain resistance and oil–water separation was demonstrated. PMHS chains with very low surface energy were grafted onto cotton fabric by the dehydrogenation reaction between –Si–H of PMHS and –OH groups of cotton fabric at room temperature. The water contact angle of PMHS-modified cotton fabric was 141.7°, which provided the modified cotton fabric with good stain resistance to waterborne pollutants. The separation efficiency of diesel from water was higher than 92% for 20 repeatable separation cycles. A further improvement in stain resistance to oil was also demonstrated by a further addition reaction of 1H,1H,2H-perfluoro-1-decene with PMHS-modified cotton fabric.

Synthesis and radiation shielding properties of polyimide/Bi2O3 composites

Radiation shielding composites based on polyimide and Bi₂O₃ were synthesized. Surface and physical-mechanical properties of polyimide/Bi₂O₃ composites were studied. Bi₂O₃ particles were modified by polymethylphenylsiloxane for the uniform distribution of filler in composites. This paper presents data on the production of composites in two ways: hot- and cold-pressing. The hot-pressing method for the synthesis of composites is preferable compared to the cold-pressing method (the density increases by 10-12%, and the Vickers microhardness by 10-20%). The results show that the introduction of Bi₂O₃ significantly increases the thermal stability of the composites. At 680 °C, a polymer composite containing 10 wt% Bi₂O₃ retains 9.7% of its mass, and at 60 wt% Bi₂O₃, retains 58.4%. The radiation-protective characteristics of the composites with respect to gamma radiation were evaluated by experimental and theoretical methods. High radiation-protective characteristics of the composites have been established in the gamma-quanta energy range of 0.1-1 MeV.

Facile spraying fabrication of highly flexible and mechanically robust superhydrophobic F-SiO2@PDMS coatings for self-cleaning and drag-reduction applications

Superhydrophobic coatings treated as surface functional materials are endowed with great application potential with respect to self-cleaning, drag-reduction, anti-icing, etc.

Thin Insulating Tunneling Contacts for Efficient and Water-Resistant Perovskite Solar Cells

Tunneling contacts made of any insulating polymers, a champion technology in silicon solar cells, are shown to increase the stabilized efficiency of perovskite solar cells (PSCs) to 20.3%. The tunneling layers spatially separate photo-generated electrons and holes at the perovskite-cathode interface and reduce charge recombination. The tunneling layers made of hydrophobic polymers also significantly enhance the resistance of PSCs to water-caused damage.

Interfacial behaviour of cubic silsesquioxane and silica nanoparticles in Langmuir and Langmuir–Blodgett films

Fluorinated polyhedral oligomeric silsesquioxanes (POSS) have been established as useful for the fabrication of superhydrophobic coatings, however little attention has been paid to their use for making ultrathin film by the Langmuir–Blodgett method.

Adjusting the stability of plasma treated superhydrophobic surfaces by different modifications or microstructures

Different time stabilities of plasma-induced hydrophilicity and wettability patterns have been realized by dissimilar microstructures.

Waterborne UV-curable comb-shaped (meth)acrylate graft copolymer containing long fluorinated and/or polysiloxane side chains

Waterborne UV-curable comb-shaped (meth)acrylate graft copolymers containing long fluorinated and/or siloxane side chains.

Tribological behavior of molybdenum disulfide bonded solid lubricating coatings cured with organosiloxane-modified phosphate binder

Hydroxyl-polysiloxane prepolymers were prepared via refluxing methyltriethoxysilane (METS) and dimethoxydimethylsilane (MSDS) at 75 °C in the presence of hydrochloric acid as the reactant.