Surface chemical coupling

An important chemical modification method is the chemical coupling method. This method improves the interfacial adhesion. The fiber surface is treated with a compound that forms a bridge of chemical bonds between fiber and matrix. 

For chromatographic sorbents it is necessary that the polymeric cover be uniformly distributed over the silica surface and chemically coupled to it. The appropriate introduction of the initiator is one of the decisive steps of this task. The first method (binding to the surface) increases the yield of grafted polymer. However in this case a large amount of homopolymer is formed. This disadvantage could be prevented by the application of hydroperoxide initiators in combination with the proper redox-agents [78-81],... 

Addition is even more facile in radical -b radical reactions due to the usually barrierless formation (on the singlet-coupled surface) of a chemical bond... 

A remaining crucial technological milestone to pass for an implanted device remains the stability of the biocatalytic fuel cell, which should be expressed in months or years rather than days or weeks. Recent reports on the use of BOD biocatalytic electrodes in serum have, for example, highlighted instabilities associated with the presence of 02, urate or metal ions [99, 100], and enzyme deactivation in its oxidized state [101]. Strategies to be considered include the use of new biocatalysts with improved thermal properties, or stability towards interferences and inhibitors, the use of nanostructured electrode surfaces and chemical coupling of films to such surfaces, to improve film stability, and the design of redox mediator libraries tailored towards both mediation and immobilization. 

Chemical modification of surface residues of HRP is one method which may offer some improvement in thermal or long-term stability of the enzyme. The -amino groups of the six surface Lys residues can be modified by reaction with carboxylic anhydrides and picryl sulfonic acid (296). In this example the number of sites modified was found to be more significant than the chemical nature of the modification, at least as a criterion for improved stability. Other methods explored include the use of bifunctional crosslinking reagents to couple surface sites on the enzyme (297). Future developments are likely to be concerned with the selection of site-directed mutants of HRP C that show enhanced thermal stability. Dramatic increases in thermal stability of up to 190-fold have been reported recently for mutants of Coprinus cinereus peroxidase (CIP) generated using a directed evolution approach (298). 

It has been shown that, with the help of irradiation, the incompatible PTFE surface can be functionalized to enhance its compatibility with rubber matrixes. A loading of 30 phr PTFE has been found sufficient to improve the mechanical and friction properties. Furthermore, the influence of radiation-induced free radicals and structural alterations on the properties of rubber compounds has been investigated. The radicals generated during irradiation are available for chemical coupling... 

The diffusion length of photogenerated charge carriers is one of the important parameters governing the efficiency of a solar cell. In conventional cells, this is an intrinsic property of the semiconductor and its purity [34]. However, in DSSCs, the diffusion length is a function of the rate of reaction (4) and, thus, varies with different redox couples, surface treatments, and so forth. When the oxidation of R [reaction (2)] is chemically irreversible, the diffusion length of electrons is effectively infinite, whereas with kinetically fast, reversible redox couples (see Section VI), it approaches zero with unpassivated interfaces. 

For consistent and reproducible operation it is important to control chemosensor features like thickness of the MIP coatings. Generally, MIPs were prepared and immobilized on PZ resonators by using two distinct procedures, namely in situ assembling on the resonator surface [103] or physical entrapment of the preprepared MIP particles in an inert polymer matrix attached to this surface [21]. Typically, thickness of the polymer is 20 nm to 5 pm. In situ immobilization of MIPs (see below in Sects. 3.2.1-3.2.4) can be accomplished by surface grafting, sandwich casting, electropolymerization, physical entrapment or chemical coupling [102],... 

If the polymer surface to be modified possesses reactive groups capable of combining other components, such as water-soluble polymer molecules, surface modification can be readily conducted by chemical coupling reaction. Numerous synthetic reactions are available for this purpose. Bergbreiter [2] reviewed various... 

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