Siliceous substrates

Zhao and Brittain [280-282] reported the LCSIP of styrene on planar silicon wafers using surface modifications of 2-(4-(ll-triethoxysilylundecyl)phenyl-2-methoxy-propane or 2-(4-trichlorosilylphenyl)-2-methoxy-d3-propane respectively. Growth of PS brushes from these SAMs has been successfully achieved factors that influence PS thickness included solvent polarity, additives and TiC concentration. Sequential polymerization by monomer addition to the same silicate substrate bearing the Hving polymer chains resulted in thicker PS films. FTIR-ATR studies using a deuterated initiator indicated that the initiator efficiency is low, and the... 

Lastly, Polystyrene (PS) brushes on silicate substrates were grafted via carbocationic polymerization from self-assembled monolayer (SAM) initiators as reported by Brittain et al The carbocationic initiators, 2-(4-(ll-triethoxysilylundecyl))phenyl-2-methoxypropane and 2-(4-trichlorosilyl-phenyl)-2-methoxy-d3-propane, and their corresponding SAMs were prepared on various substrates. The monolayers were characterized by FTIR-ATR, contact angles, and X-ray reflectometry. The growth of the PS brushes from... 

Hydrosilation chemistry is presently having, and will continue to have, an important impact on certain areas of materials chemistry. The rapidity and cleanliness of the reaction, and the stability of the resulting Si-C bonds, have been used to produce dendritic polymers and block copolymers with well-defined structures [21]. The reaction can also be employed to attach molecules to surface Si-H groups, notably the Si-H present on the surfaces of aqueous etched single crystal, or nanoparticular Si [22], or other siliceous substrates, with substantial modification to their physical and chemical properties [23]. 

It is known that organosilicon compounds attach themselves outstandingly to silicate substrates, but not always to calcium carbonate [19, 20]. A surprising finding was that polymeric silicones attach... 

All silica immobilized phase transfer catalysts previously reported involve two or more steps for the immobilization. Problems with preparations of this type include the difficulty in obtaining maximum functionality on the substrate and residual substrate bond intermediates which may interfere in final applications. The purpose of this work was to prepare well-characterized functionalized phase transfer catalysts that could be immobilized on siliceous substrates in a single step. As will be shown the preparation of functionalized onium catalysts proceeds readily. The route to facile immobilization of crown ether was not so direct. Avenues for high yield chemistry employing accessible or economic intermediates were not available. A new class of crown ethers which are readily functionalized during synthesis was developed. We have designated than "silacrowns". This report concentrates upon the properties and characterization of these new phase transfer catalysts. 

The nature of the indigo-palygorskite association and the reasons for the hue and durability of MB have become controversial. Thus, Jose-Yacaman et al. (1996) reported the presence of nanoparticles of iron metal encapsulated in an amorphous silicate substrate accompanied by iron oxide nanoparticles on the surface of that substrate. On the basis of those observations, it was suggested that Mie-type light dispersion in nanoparticles should produce the characteristic hue of MB. 

Siliceous substrates are used extensively in industry and applied research. These materials can undergo a variety of chemical modifications that make them useful for applications such as catalysis and chromatography. An increased understanding of the nature of surface reactions and reaction products would facilitate current and future applications of these... 

Acidity of siliceous substrates, characterization methods, 258 Activated silica, 150 °C exchange data for reactions, 192-193,194f, reaction time vs. surface hydroxyl groups, 188,189f... 

Evidence is accumulating of the existence of Si-O-M bonds in a variety of FTIR and SIMS studies of thin films of silanes on non-siliceous substrates. Examples where M is Ti, Al, Fe, Cr and Pb have all been reported (see Cave and Kinloch for a recent review). Our self-assembled monolayer studies of alkylhydridosilanes on silver have shown a new peak in the FTIR spectrum at 960 cm which we tentatively identify with Si-O-Ag linkage formation. ... 

Glassy polymeric materials were prepared by heating sodium plumbite-treated cotton in contact with a siliceous substrate The glassy polymeric materials resemble petrified cotton and contain considerable carbon They resist acid and alkali are hard and can serve as labels decorations adhesives between glasses or colored coatings ... 

The novel mechanism by which these glassy materials are formed involves movement of silicon from the substrate across the Interface to the carbonaceous skeleton of the treated cotton The migration in solid states occurs at temperatures considerably below the melting point of either the siliceous substrate or polymeric plumbous oxide The relatively low temperature of the process suggests that interpenetration by the silicon occurs by an interstitial mechanism ... 

The plumbite treated fabric cut to desired shape is heated in a closed oven to approximately 600 0 with the fabric in surface contact with either a silicate glass or porcelain It is important that the oven remain closed while the temperature is raised to about 300 C to prevent ignition of the fabric Above 300 C the oven can be opened periodically for examination of the sample The temperature of 600 C is maintained for about 1 h The maximum temperature required will vary soiaewhat depending on the siliceous substrate used Temperatures as low as 550 C with soda-lime glass and as high as 700 C with borosilicate glasses have been used with success ... 

When two materials are bonded the resultant composite has several constituents and interfaces, as depicted for example in Fig. 3.2. Being liquid, adhesives flow over and into the surface irregularities of a solid, so coming into intimate contact with it and, as a result, interatomic forces are brought into play. Adhesives therefore join materials primarily by attaching to their surfaces within a layer of molecular dimensions, i.e. of the order of 0.1-0.5 nm. In joints involving metallic or siliceous substrates, the adhesive sticks to the surface oxide layer and not to the solid itself. In simple terms, there is an obvious conflict between having an adhesive material which... 

Zhao, B., and Brittain, W. J. (2000). Synthesis, characterization, and properties of tethered polystyrene-b-polyacrylate brushes on flat silicate substrates. Macromolecules, 33(23) 8813-8820. 

Zhao, B., Brittain, W.J. 2000. Synthesis, Characterization, and Properties of Tethered Polystyrene-b-Polyacrylate Brushes on Flat Silicate Substrates. Macromolecules 33 8813-8820. 

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