Showing papers on "Surface modification published in 1978"

Enhanced photoelectrochemical solar‐energy conversion by gallium arsenide surface modification

Abstract: In the n‐GaAs/Se=–Se=x–OH−/C liquid junction solar cell, modification of the semiconductor surface by incorporation of ruthenium increases both the fill factor and the open‐circuit voltage and improves the reproducibility of performance. The power conversion efficiency of the modified cell is 12% under ∼100 mW/cm2 sunlight. Surface metal atoms or ions are shown to alter GaAs cell behavior widely; Ru represents a case for which the effect on cell performance is both positive and persisting.

Effect of surface modification on solid-liquid interfacial adsorption of mixtures

Abstract: A study was made on the adsorption of methanol-benzene mixtures on organophilic montmorillonites with surfaces modified to various extents. The effect of the extent of surface modification on the shapes of the excess isotherms was established. A model isotherm equation was given taking into account, among others, the polar-apolar surface area ratio of the adsorbent.

Surface Modification of Proteins

Abstract: The covalent bonding of proteins to soluble polymers is closely related chemically to immobilization. Reactions similar to the activation of polymers are used. Polymers with a chemical structure similar to those used for solid phases and surfaces (gels, membranes, coatings) may be used. The disadvantage of using soluble polymers instead of insoluble compounds is the more laborious purification needed after polymer activation and reaction with the protein. The excessive reagent and unreacted protein have to be separated by precipitation (often with organic solvents), gel filtration, ultrafiltration or dialysis.

Surface modification of high polymer base material

Abstract: PURPOSE: To improve the adhesion, printability, and coating performance of the material without degrading its properties, by grafting an ethylenically unsaturated monomer onto a high polymer base material whose surface is impregnated with a photosensitizer. CONSTITUTION: The surface of a high polymer base material is impregnated with a solution of a photosensitizer, e.g. benzoin ether, and irradiated with actinic rays, preferably a mercury lamp, of 250W700nm while in contact with a solution of an ethylenically unsaturated monomer, e.g. maleic anhydride. The monomer is thus grafted to modify the surface layer only. Preferably, a hydrophilic monomer is grafted onto a hydrophobic material, and vice versa. USE: Materials for printing plates and medical use. COPYRIGHT: (C)1980,JPO&Japio

Anodic functionalization of 1H-perfluoroalkanes. Observation of 19F C.I.D.N.P.

Abstract: The anodic oxidation of 1H-perfluoroalkanes in HSO3F–KSO3F (0·5M) leads to perfluoroalkyl fluorosulphates, through an indirect process as confirmed by 19F C.I.D.N.P.

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. III. Oxidative degradation and stabilization of grafted layer

Abstract: Vapor-phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) and subsequent saponification treatment produce a surface graft having a high adhesive bondability, which results from the presence of a hydrolized homopolymer layer (consisting of only monomer componenet) on an inner graft copolymer layer consisting of both PE and monomer components. The oxidative deterioration and the stabilization of the grated surface layer have been investigated to clarify the long-term stability of the adhesive bondability. The bondability rapidly disappears with accelerated weatherly followed by acetone extraction treatment, whereas it is kept unchanged during thermal-oxidative aging at 100/sup 0/C. Microscopic and attenuated total resonance (ATR) infrared spectroscopic observations of the degreaded surfaces show that the bondability loss is due to degradiative removal of the surface homopolymer layer. The addition of combinations of conventional antioxidants and ultraviolet absorbers stabilizes the grafted surface layer against thermal-oxidative and photo-oxidative degradation and thus extends the bondability rentention time. The stabilization is more effective in the grafts of carbon black-containing PE, where carbon black is present in the inner-graft copolymer layer.

Surface Analysis of Polymer and Glass

Abstract: The unique physical nature of glass results in numerous surface phenomena which have long been unexplained due to difficulties experienced by analytical chemists undertaking their study. Modern, sophisticated surface analysis instrumentation now permits analysis of surfaces from the top monolayer into the bulk material. Detailed studies of glass surfaces provide the information necessary to understand how common cleaning, polishing, etching, and heat treatments affect the chemistry and properties of glass. Similar information obtained from studies of the first 30A of treated polymers contributes to the understanding and explanation of their properties such as those related to oxidation, degradation, reflectance, hardness, and especially adhesion. The primary objective achieved through detailed surface analysis of the treated polymers was the knowledge necessary to develop better adhesion to polymers. Problems inherent in surface analysis of glass and polymers relate to their physical nature. Their surfaces are highly subject to ion migrations which are disconcerting to the analyst. The nonconductive or electrical insulating property defeats many instrumental methods of analysis. Combined high-performance ion scattering spectrometer (ISS), utilizing a recently developed cylindrical mirror analyzer (CMA), and a secondary ion mass spectrometer (SIMS) were used in these studies. The system was also equipped with a charge neutralization system and an automatic high-speed data processing device. Common soda lime glass was subjected to treatment by chromic acid, alcoholic potassium hydroxide (KOH), hydrogen fluoride (HF) vapor, and HF bath, and studied from the top monolayer to several hundred angstroms. Zirconium polished glass and various heat-treated glasses were studied similarly. Results were compared to analysis of the surface and bulk of untreated glass. A commercial polyimide, Kapton, cleaned by acid, base, solvents, and various drying techniques was surface analyzed. Surface information was correlated with original and residual contaminants and thin film bondability. Results indicated that most glasses are normally surface rich in sodium from 0 to about 30A, but chemical cleaning by chromic acid, KOH, and HF vapor removes surface sodium, leaving a surface of primarily silica only. Heat treatment caused extensive concentration changes to several thousand A. The surface carbon, nitrogen, and oxygen concentrations of a polyimide were substantially altered by simple cleaning treatments to about 30A. However, the surface exhibiting greatest bondability of coated aluminum showed minimum contaminations due to metal such as sodium, magnesium, aluminum, silicon, potassium, calcium, and fluorine. The combined results illustrate that the extensive surface information available through modern analyrical instrumentation contributes substantially toward understanding and controlling surface phenomenon not previously explained.

Organometallic polymers. V. Synthesis and properties of metallocene‐modified polymers

Abstract: The reaction of metallocenes with solutions of polydienes and halogenated polymers, under Friedel-Crafts conditions, has now been applied to the surface modification of solid polymer films. The reaction of ferrocene with chlorinated polyethylene films appears to proceed by a fast substitution step followed by a slower diffusion-controlled step. The stress–strain curves of surface-modified films, as well as of solution-cast polymetallocene films, have been examined by means of a bursting-strength apparatus. The weathering behavior of metallocene-modified polymers has been studied in both natural and accelerated conditions. Studies on the effect of ageing on composition and properties by spectrophotometric and mechanical measurements indicate that the photooxidative resistance of polymers is improved significantly by metallocene modification. Additionally, modified films have been found to be effective as clear shields for the protection of vulnerable substrates against photodegradation. The observed darkening of the irradiated films could be due to a thermal reaction between metallocene and photolytically generated macroperoxides.

Regioselective functionalization of triamantane

Abstract: Durch Umsetzung von Triamantan (Ia) mit Brom bei 0°C fur 5 - l0 Min. und anschliesende Hydrolyse in heisem wasrigem Dimethylformamid erhalt man die Alkohole (Ib)-(Id) im Verhaltnis 73: 23:3.

Total synthesis of indole and dihydroindole alkaloids. xii. selective functionalization of various bisindoles. efficient syntheses of leurosine and related bisindole alkaloid derivatives

Abstract: Studies involving selective functionalization of the indole unit in a number of bisindole alkaloids and related synthetic derivatives are described. These investigations include such reagents as te...

Surface modification of molded article of fluororesin

Abstract: PURPOSE:To roughen the surface of a molded article of fluororesin readily without using noxious dangerous chemicals and to improve the affinity for additives, by molding a fluororesin in close contact with the surface of a metal molded article having a specific surface roughness.