RF-PACVD of water repellent and protective HMDSO coatings on bell metal surfaces: Correlation between discharge parameters and film properties

Hexamethyldisiloxane (HMDSO) films have been deposited on bell metal using radiofrequency plasma assisted chemical vapor deposition (RF-PACVD) technique. The protective performances of the HMDSO films and their water repellency have been investigated as a function of DC self-bias voltage on the substrates during deposition. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. Optical emission spectroscopy (OES) analyses of the plasma during deposition reveal no significant change in the plasma composition within the DC self-bias voltage range of −40 V to −160 V that is used. Raman and X-ray photoelectron spectroscopy (XPS) studies are carried out for film chemistry analysis and indicate that the impinging ion energy on the substrates influences the physio-chemical properties of the HMDSO films. At critical ion energy of 113 qV (corresponding to DC self-bias voltage of −100 V), the deposited HMDSO film exhibits least defective Si-O-Si chemical structure and highest inorganic character and this contributes to its best corrosion resistance behavior. The hardness and elastic modulus of the films are found to be bias dependent and are 1.27 GPa and 5.36 GPa for films deposited at −100 V. The critical load for delamination is also bias dependent and is 11 mN for this film. The water repellency of the HMDSO films is observed to be dependent on the variation in surface roughness. The results of the investigations suggest that HMDSO films deposited by RF-PACVD can be used as protective coatings on bell metal surfaces.     

Fabrication of superhydrophobic polyaniline films with rapidly switchable wettability

A superhydrophobic polyaniline (PANI) film has been fabricated by using a facile one-step spraying method. The PANI was synthesized via in situ doping polymerization in the presence of perfluorooctanoic acid (PFOA) as the dopant. The water contact angle of this superhydrophobic surface reaches to 156°. Both the surface chemical compositions and morphological structures were analyzed. A granular morphology of PANI with a moderate amount of nanofibers was obtained. Moreover, a rapid surface wettability transition between superhydrophobicity and superhydrophilicity can be observed when it is doped with PFOA and de-doped with base. The mechanism for this tunable wettability has been discussed in detail.     

Fabrication of durable hydrophobic surfaces through surface texturing

Low surface energy polymer thin-films can be applied to surfaces to increase hydrophobicity and reduce friction for a variety of applications. However, wear of these thin films, resulting from repetitive rubbing against another surface, is of great concern. In this study, we show that highly hydrophobic surfaces with persistent abrasion resistance can be fabricated by depositing fluorinated carbon thin films on sandblasted glass surfaces. In our study, fluorinated carbon thin films were deposited on sandblasted and as-received smooth glass using deep reactive ion etching equipment by only activating the passivation step. The surfaces of the samples were then rubbed with FibrMet abrasive papers in a reciprocating motion using an automatic friction abrasion analyzer. During the rubbing, the static and kinetic friction forces were also measured. The surface wetting properties were then characterized using a video-based contact angle measuring system to determine the changes in water contact angle as a result of rubbing. Assessment of the wear properties of the thin films was based on the changes in the water contact angles of the coated surfaces after repetitive rubbing. It was found that, for sandblasted glass coated with fluorinated carbon film, the water contact angle remained constant throughout the entire rubbing process, contrary to the smooth glass coated with fluorinated carbon film which showed a drastic decrease in water contact angle with the increasing number of rubbing cycles. In addition, the static and kinetic friction coefficients of the sandblasted glass were also much lower than those of the smooth glass.     

Aminocalix[4]arene: the effect of pH on the dynamics of gate and portals on the hydrophobic cavity

The pH of a solution shows a significant effect on the dynamics of the gate (formed by eight benzylic functions) and portal on the hydrophobic cavity of receptor. At pH 5.8 the gate closes and prohibits the entry of anionic guests. However, at pH 7.3 the gate opens and allows the entry of anionic guests into the hydrophobic cavity. It is the first time that anionic receptor efficiently recognizes anionic guests.     

Significance of hydrophobic interactions in water–organic binary solvents

A LFE (Linear Free Energy) analysis of kinetic data for different organic reactions in various organic aqueous solutions was carried out. The rate constants of these reactions were compared with those for the solvolysis of tert-butyl chloride in the same solvents in terms of the LFE Relationships, and linear plots were observed in a wide range of the co-solvent content. This similarity points to a common nature of the solvent effect in these reactions in variety of water–organic mixtures, regardless of largely different reaction mechanisms. We explain these results by the prevalence of hydrophobic stabilization of the initial state of these reactions in water-rich solvent mixtures. Recently the same conclusion was also made on the basis of investigations into sonication effects in kinetics of organic reactions. A considerable contribution of hydrophobic effects to the Y scale by Grunwald and Winstein was deduced.     

Raman scattering spectra of Aerosol-OT homologous sodium dialkylsulfosuccinates and the environment of their hydrophobic chains

 A homologous series of sodium dialkylsulfosuccinates (SDAS) has been synthesized with various chain lengths (dibutyl, dihexyl, diheptyl, dioctyl, dinonyl, didecyl, diundecyl and didodecyl). These compounds are straight-chain analogues for Aerosol-OT. Raman scattering spectra have been recordered for these SDAS compounds, both in the solid state and in aqueous solutions. These spectra are analyzed in detail in the CH stretch and CH₂ deformation regions, and the results depend specifically on the length of the hydrocarbon chain. In particular, the longitudinal accordion-like vibrational modes coming from the all-trans n-alkyl chains have been investigated. For the SDAS dihydrates, all hydrocarbon chains take up an extended form, whereas for the monohydrates the tails tend to become disordered at the CH₂-CH₂ single bond close to the terminal methyl groups. It has also been confirmed that for the concentrated aqueous SDAS (sodium dibutylsulfosuccinate – sodium dioctylsulfosuccinate) samples preferential stabilization of the extended conformation of the hydrocarbon chain may occur. Received: 23 February 1999 Accepted: 10 May 1999     

Versatile self-assembled hybrid systems with exotic structures and unique functions

In this review article, we describe recent progress about exotic self-assembled systems with various dimensions including biomolecules, supramolecules, unique hydrophobic amphiphiles, polymers, nano-clusters, and colloidal particles. Construction of robust biomolecular assemblies with exotic structures, such as ring and hollow capsule, is achieved by rational designs of symmetric biomolecular conjugates. In addition, we comprehensively summarized leading-edge topics on optical/topological properties of self-assembled hybrid systems, such as circularly polarized luminescence or structural color. The preparation of colloidal amorphous array with photonic band gap-induced angle-independent structural color is also achieved in consideration of the following situations: i) two-body sphere–sphere potential, ii) disorder packing using different sizes of colloidal particles, and iii) softness of colloidal particles. Lastly, we demonstrated useful utilizations of exotic self-assembled objects. Flakelike microparticles were transcribed into various nano-flake metals and applied as temperature indicator for the local heating of an addictive. All findings described here show meaningful hybrid strategies in self-assembly techniques and their functionalization as well as materialization.     

Synthesis and cationic photopolymerization of new silicon‐containing oxetane monomers

The cationic photopolymerization of oxetane‐based systems containing silicon monomers was investigated. For this purpose, three new silicon‐containing oxetane monomers were synthesized through a simple and straightforward synthetic method. The silicon‐containing monomers were added to a typical oxetane resin, 3,3′‐[oxydi(methylene)]bis(3‐ethyloxetane), in concentrations of 1–5 wt %. They exploited a certain surface tension effect without affecting the rate of polymerization. Enrichment only on the air side was achieved, which induced hydrophobicity in the photocured films, depending on the monomer structure and concentration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1415–1420, 2004     

室温固化疏水性聚合物涂层研究

结霜问题广泛存在于制冷和低温领域并降低制冷系统的运行效率及运行稳定 .为防止在材料表面附着小水滴并结霜 ,通常的表面改性方法有 :(1 )涂敷亲水性聚合物[1] ,通过提高表面的亲水性来使水滴铺张 ,但附着的水滴易使表面膨胀、强度降低并破坏与基材的粘结力 ;(2 )涂敷疏水性聚合物 ,它们一般含有大量低表面能的硅、氟等原子基团 ,通过提高表面的疏水性来提高表面对水滴的接触角 ,并使水滴滑落 ,但通常认为涂层对基材的粘接力低且强度及耐久性差[2 ] .氟树脂涂料具有优良的耐候性、耐腐蚀性、耐沾污性、耐热性、耐化学品性、斥水斥油性、绝…     

Effects of oxidation and surface roughness on contact angle

Contact angle is known to be a parameter that effects boiling. This study was undertaken to measure contact angle of high and low surface tension fluids on copper and aluminum surfaces.Data were taken for polished, oxidized, and rough surfaces. A simple, yet fairly accurate method of measuring the static equilibrium contact angle of a solid/liquid interface is presented. The principles of a line light source and tilting plate were modified and then combined in the design of this apparatus. The angles obtained and their variation with the solid surface properties were in good agreement with previously published data. The contact angle of distilled water o of the organic fluids and refrigerants tested were in the range of 2–5°. Roughness and oxidation reduce the contact angle. If the depth of the roughness is less than 0.5 μm contact angle. The apparatus is fairly simple in construction, is inexpensive, and has good reproductibity. The measured angles were then compared to those measured with the sessile drop method.