Organic Polymer Coatings

Organic polymer coatings were developed by Puddington and Sirianni. Silicas were made organophilic with polymers of polystyrene, linseed oil, and alkyd resin (540, 541). A polymer coating of the reaction product of a polyisocyanate and a polyol 

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The important item is that this coating can be applied at room temperature and cured at 90 °C and gives a clear film with optical quality. Typical properties of inorganic polymers (hardness) and organic polymers (coating as a lacquer and low temperature processing) could be combined in one and the same polymer. 

They explain three types of immobilization procedures (1) physical adsorption of reagent onto the solid matrix, (2) covalent attachment of a reactive tag through a chemical bond with silanols on the silica surface, and (3) covalent attachment of a reactive tag to an organic polymer coating on the silica surface. 

In a non-hermetic package, the primary moisture barrier is typically a thin, (<0.1 micron) inorganic passivation layer of silicon dioxide or silicon nitride. However, passivation layers cannot withstand physical handling and they are not resistant to saline exposure. Additional protection is needed in the form of organic polymer coatings. 

For this reason, encapsulation is used to isolate devices from their external surroundings. Encapsulants comprise a variety of materials viz., metals, inorganic glasses, and conformal organic polymer coatings. Each has the same function, to act as a protective molecular barrier. 

Poly(indole) has found applications as an organic polymer coating. The performance of layered semiconductors has been shown to be improved by the electropolymerization of layers of poly (indole) on the defective sites of the surface. Carbon fibers may be coated with poly(indole) by electropolymerization. More recently, poly(indole) has been employed for the polymer coating for a glucose sensor [125]. 

Nitrogen Adsorption. Book of Standards Volume 09.01. Pennsylvania ASTM International Azuta K. Tadanaga K., Minami T. Water and oxygen permeability of silica thin films contaiiting organic polymers coated on poly (ethylene terephtalate) by the sol-gel method. J. Ceram. Soc. Jpn. 1999 107 293-296... 

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