Silane-solid surface interaction

The deposition of molecular films on solid substrates was initially of the Lang-muir-Blodgett type [186, 187], where layers preformed on a liquid-air interface are carefully transferred on to a solid surface. The difficulties associated with deposition of LB films are overcome in systems where molecules from a solution phase assemble themselves on a solid surface in the form of a one molecule thick film. If the interaction between the head groups of the molecules with the substrate surface is of the covalent type, as in the case of surface silanization [188, 189], then we can expect the film to be mechanically robust. 

Some contributions cover the development of specific materials and analytical methods to measure the characteristic properties of solid particles, such as particle sizes, surfaces areas, mechanical strengths, or solid-matrix interactions. Thus, papers from M. Heinematm and S. Hild deal with the characterization of silica-polymer interactions using Scanning Force Microscopy, while C. Panz uses the combination of special basic silica, fitting silanes, and adequate hydrophobization conditions to generate high-performance silica with new properties. 

Measurements of surface energy and wettability of a surface by different liquids may provide an additional insight into surface properties of silanized glass surfaces, the structure of the coatings, and the mechanism of interfacial interactions. Theoretically, solid surface tension energy is composed of two additive terms ... 

An additional level of complexity is encoimtered when silanes are added in the presence of solid surfaces. Hydrolyzed or imhydrolyzed coupling agents will interact with a variety of oxide surfaces. Even in the case of metal fillers, an oxide layer is often found at the surface. The presence of water at these interfaces may... 

Conversely, DNA is functionally and structurally more stable than proteins it is easier to handle and interacts more favorably with surfaces. This provides a larger window for the choice of substrate, as well as for variations in attachment strategies. Many different schemes have been developed for immobilization of DNA and oligonucleotides on solid surfaces. Some thoroughly studied routes include covalent or electrostatic linking via functional silanized monolayers (see below), self-assembly of thiol-derivatized oligonucleotides on gold surfaces (Steel, 1999), or assembly of LB monolayers at the air-water interface (Okahata, 1996 Ijiro, 1996). 

Solid supports should be chemically inert and exhibit a large surface area. Support materials used are diatomaceous earths. Teflon , glass beads, and various polymers. Since the surface of the diatomaceous materials consist of silanol (Si—O—H) and siloxane (Si—O—Si) groups, compounds capable of hydrogen bonding (alcohols, acids, amines, etc.) can interact with these media, which results in tailing. This problem may, however, be minimized by silanization ... 

A further illustration of IGC as a source of data for acid/base characterization of polymers and of solid constituents of complex polymer systems, is given by Osmont and Schreiber (49), who rate the inherent acid/base interaction potentials of glass fiber surfaces and of polymers by a comparative index, based on the Drago acid/base concepts (SO). The interaction index is conveniently measured by IGC and is shown to differentiate clearly among untreated and variously silane-modified glass fiber surfaces. Conventional methods are used to determine adsorption isotherms for fiber-polymer pairs, and the IGC data ate used to demonstrate the relationship between acid/base interactions and the quantity of polymer retained at fiber surfaces. 

Physical and chemical mapping using AFM and ToF-SIMS are appropriate means for studying surfaces of flame retarded materials. Various interactions may take place between ammonium polyphosphate (APP), pentaerythritol (PER) and tetraethoxy-silane (TES). Whereas the reaction between APP and PER has been described [820], no direct reaction could be found between APP and TES. Marosi et al. [821] have reported imaging ToF-SIMS of APP-PER-ME-TES intumescent flame retarded (IFR) polypropylene. The image prepared on the basis of SiOjc ions proved the existence of a silicone layer between polymer and solid APP particles covered by PER. 

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