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Patent Issued for Transparent Inorganic-Organic Hybrid Materials via Aqueous Sol-Gel Processing

June 4, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Asuka, Masahiro (Mount Laurel, NJ); Sigmund, Wolfgang M. (Gainesville, FL), filed on September 11, 2009, was published online on May 20, 2014.

The assignee for this patent, patent number 8728579, is University of Florida Research Foundation, Inc. (Gainesville, FL).

Reporters obtained the following quote from the background information supplied by the inventors: "Transparent coatings from sol-gel techniques that closely approximate inorganic glasses are commonly formed from alcohols or other non-aqueous solvents. For example, to obtain a continuous transparent coating, a TiO.sub.2 glass is often formed from condensation of a tetraalkoxytitanate in the presence of a chelating agent in an alcohol solvent or under restricted conditions, such as synthesis in a glove box. Aqueous solvents, or even using a large quantity of water during the process, generally promote the condensation of precursors into particulate glasses. Even when non-aqueous solvents are used, the formation of a hard robust coating is problematic as the resulting glasses often have a tendency to crack because of shrinkage induced stresses upon evaporation of solvents and the loss of condensation byproducts. Because of this propensity for cracking, coating thicknesses in excess of 1.5 .mu.m generally require that multiple thin coating layers are made, usually with practical limits of 20 to 30 coats. The formation of thick single layer coatings is often achieved in a non-aqueous system by the use of an inorganic/organic composite, an organically modified ceramic, where an organic component is included in a colloidal sol-gel system. Generally there is little interpenetration of these inorganic and organic portions, and high hardness with optical transparency is generally not achieved in such systems.

"As the use of organic polymer based devices, such as LCD displays and LED lighting, increases, there is a greater need for thick superior abrasive resistant transparent coatings that have excellent barrier properties for plastic or other organic substrates, and where the processing can be carried out with the formation of a single coating layer in a manner that does not damage the underlying substrate. Hence the formation of a transparent hard coating with high solids that act as an excellent diffusion barrier for an underlying substrate remains a need."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Embodiments of the invention are directed to an inorganic-organic hybrid coating where a sol-gel glass is derived from a sol having at least one hydrolyzable silane, where at least one silane contains at least one polymerizable organic group attached to the silane, and at least one hydrolyzable metal oxide precursor. The sol is free of organic solvents in excess of that which can be formed upon hydrolysis of the silane and metal oxide precursor. The silanes are of the structure R.sub.(4-n)SiX.sub.n where: n is 1 to 4; X is independently a hydrolyzable group selected from C.sub.1 to C.sub.6 alkoxy, Cl, Br, I, hydrogen, C.sub.1 to C.sub.6 acyloxy, and NR'R'' where R' and R'' are independently H or C.sub.1 to C.sub.6 alkyl, C(O)R''', where R''' is independently H, or C.sub.1 to C.sub.6 alkyl; and R is independently C.sub.1 to C.sub.12 radicals, optionally with one or more heteroatoms, including O, S, NH, and NR'''' where R'''' is C.sub.1 to C.sub.6 alkyl or aryl. The radical can not be hydrolyzed from the silane and contains a group capable of undergoing polyaddition or polycondensation reactions, selected from Cl, Br, I, unsubstituted or monosubstituted amino, amido, carboxyl, mercapto, isocyanato, hydroxyl, alkoxy, alkoxycarbonyl, acyloxy, phosphorous acid, acryloxy, metacryloxy, epoxy, vinyl, alkenyl, or alkynyl. In one embodiment the silanes are tetraethoxysilane (TEOS) and .gamma.-glycidoxypropyltrimethoxysilane (GPTMS). The metal oxide precursor can be MX.sub.n where: n is 2 to 4; M is a metal selected from the group consisting of Ti, Zr, Al, B, Sn, and V; and X is a hydrolyzable moiety selected from the group C.sub.1 to C.sub.6 alkoxy, Cl, Br, I, hydrogen, and C.sub.1 to C.sub.6 acryloxy. In one embodiment, the metal oxide precursor comprises titanium tetrabutoxide (TTB).

"The sol and subsequent coating can contain dispersed nanoparticles that are oxides, oxide hydrates, nitrides, or carbides of Si, Al, B, Ti, or Zr in the shape of spheres, needles, or platelets. For example, the nanoparticles can be SiO.sub.2, TiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, Al(O)OH, Si.sub.3N.sub.4 or mixtures thereof. Typical nanoparticles can be 2 to 50 nm in cross section. In one embodiment, the nanoparticles can be boehmite rods, platelets, or a combination thereof.

"Other embodiments of the invention are directed to a method for coating a substrate with an inorganic-organic hybrid material of a combined sol with the compositions described above, where at least one silicate sol, having at least one hydrolyzable silane, where at least one of the silanes has at least one polymerizable organic group attached to the silane and a stoichiometric excess of water, is added to a metal oxide sol, having at least one metal oxide and at least one hydrolyzable silane having at least one polymerizable organic group attached to the silane with less than a stoichiometric amount of water relative to the silanes and metal oxide precursors, to form the combined sol. This combined sol is coated on a substrate and gelled to form a coating that is transparent to visible light. The coating with a thickness of at least 2 .mu.m has a transmittance of at least 95%. In embodiments of the invention, nanoparticles can be dispersed in the combined sol. Coating can be carried out by any technique including dipping, spreading, brushing, knife coating, rolling, spraying, spin coating, screen printing, and curtain coating. Gelling can be carried out at ambient conditions or by heating as constrained by the substrate upon which the coating is formed. For example the substrate can be an organic material such as a thermoplastic and gelation can be carried out below the glass transition temperature of the thermoplastic."

For more information, see this patent: Asuka, Masahiro; Sigmund, Wolfgang M.. Transparent Inorganic-Organic Hybrid Materials via Aqueous Sol-Gel Processing. U.S. Patent Number 8728579, filed September 11, 2009, and published online on May 20, 2014. Patent URL:

Keywords for this news article include: Silanes, Nanoparticle, Nanotechnology, Emerging Technologies, Organosilicon Compounds, University of Florida Research Foundation Inc.

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Source: Journal of Engineering

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