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Patents of interest.

The patent is a legal document giving the holder a license to capitalize on his or her invention without competition for a few years. In exchange, the holder teaches us the basis of the invention. The patent is forward-looking, representing a technical horizon.

Shaped Copolymers

U.S. Patent 7,101,937 (September 5, 2006), "Dendritic Based Macromolecules," Jean M.J. Frechet, Craig J. Hawker, and Karen Wooley (Ithaca, New York).

Polymer molecules in the shape of kites, barbells, and knots are made by reacting dendritic copolymers with linear chains. (Reactive sites on the dendrites are reacted with the end groups of the linear polymers. This coupling of the dendritic and linear polymers involves the appropriate reaction such as ester or amide formation and vinyl addition.) The kites consist of dendrites with interconnected branches attached to a long linear polymer. The barbells have dendrites attached at the ends of a linear chain. The knots are copolymers with mixed and twisted chains attached to dendrites. These shaped copolymers are used in drug-delivery systems, imaging materials, molecular devices, thin film devices, surface modifiers, transport agents, compatibilizers, rheology-control agents, molecular ball bearings, molecular dipoles, nonlinear optical materials, membrane and cell modifiers, complexing agents, adhesives, and interface-strengthening agents.

Cationic Polymerization

U.S. Patent 7,105,615 (September 12, 2006), "Synthesis Method for Polydimethylketene by Friedel-Craft Cationic Polymerization of Dimethylketene," Reinhard Linemann and Guillaume Le (Arkema, Puteaux, France).

Lewis acid catalysts can form beta-ketone polymers with a high selectivity and yields that are too low-less than 65%--to be commercially useful. This is caused by competing initiation reactions, such as the reaction between moisture and the Lewis acid and the Lewis acid dissociation. Polar solvents are necessary to separate the charges developed by the dissociation and to limit the formation of trimers. These polar solvents, such as nitrobenzene, other nitro solvents, and chloroform, restrict large-scale production because of their toxicity. The toxic polydimethylketene also has a tendency to form explosive peroxides, affecting commercial viability. These problems can be avoided with a cocatalyst that moderates the active polymerization. The cocatalyst has a double bond, electron-depleted by an electroattractive group including o-chloranyl (3,4,5,6-tetrachloro-1,2-benzoquinone), p-chloranyl (2,3,5,6-tetrachloro-1,4-benzoquinone), nitrobenzene, trinitrobenzene, or tetracyanoethylene. The final catalyst system consists of the initiator, a catalyst, and a cocatalyst. The catalyst is a Lewis acid and the initiator is a Bronsted acid, such as a halogenated compound. It is possible to direct the polymerization toward the formation of a beta-ketone polymer with good yields, greater than 65%, in the presence of safer, conventional, inexpensive solvents, enabling economic and safe large-scale synthesis of polydimethylketene.

Crosslinked Optical Devices

U.S. Patent 7,105,621 (September 12, 2006), "Polymers for Use in Optical Devices," Andrew B. Holmes, Xiao-Chang Li, Carl S. Moratti, Kenneth A. Murray, and Richard H. Friend (Cambridge Display Technology Ltd., Cambridge, Britain).

Optical devices fabricated from soluble polymers are susceptible to solvents with changes in morphology affecting their luminescence. The luminescent film formed from a soluble polymer can be stabilized with crosslinking. This crosslinking, however, must retain semiconductive and luminescent properties. For example, effective crosslinking agents are azides, which decompose when heated to 200[degrees]C. Polymethacrylates with oxadiazole, distyrylbenzene, and cinnamate side chains can be crosslinked by radiation. The resulting polymer emits blue light efficiently and can be used in blue light--emitting devices using aluminum cathodes. The spin-coated emissive polymer can be easily cured by ultraviolet radiation to become insoluble and more stable.

Capped Polycarbonates

U.S. Patent 7,105,626 (September 12, 2006), "Method for Incorporating Alkyl Ester Endgroups To Improve the Release Properties of Melt Polycarbonate," Hans-Peter Brack, Dennis Karlik, and Jan Pleun Lens (General Electric Company, Schenectady, New York).

Polycarbonates prepared by melt transesterification contain 7% to 50% uncapped chains, more than that of interfacially prepared polycarbonates. These uncapped chains affect properties, making capping necessary. Capping can be accomplished by adding end-capping reagents during or after polymerization. Alkyl ester end-capped polycarbonates, produced by combining the free terminal OH groups with symmetrical activated carbonates and alkyl esters, have improved release properties and improved stability. The alkyl esters may be included as an additive, but they "plate out" during molding, which is a problem. Plate-out is avoided when capping agents are incorporated as end groups of the polymer chains. Glycerol-mono-stearate and pentaerythritol-tetra-stearate are good capping agents.

Reversible Crosslinking

U.S. Patent 7,105,630 (September 12, 2006), "Compound Having Thermally Dissociatable Thioacetal Skeleton, Precursor Thereof, Cured Product Thereof, and Composition for Their Production," Wonmun Choi and Hiroyuki Okuhira (The Yokohama Rubber Co., Ltd., Tokyo, Japan).

Thermosets with thioacetals have thermally reversible crosslinks. Such reversible softening or liquefaction below the thermal decomposition temperature is useful in sealants, coatings, and adhesives, and enables recycling. Thioacetals may be used as curing agents for polyurethanes, epoxies, or even as a self-curable material. They can also be used for thermal recording or heat storage and may be thermally dissociatable monothioacetals or dithioacetals. The example described in this patent includes a thioacetal with two terminal groups including hydroxyl, thiol, or carboxyl groups. The thioacetal compound may be part of the polymer chain in which the monothioacetal or dithioacetal group is included in the repeating unit. This reversibility is shown by the addition product of thiol and vinyl ether formed by reacting 1,8-dimercapto-3,6-dioxaoctane with 2 equivalents of isobutyl vinyl ether.

Fabricating Composites

U.S. Patent 7,108,821 (September 19, 2006), "Method for Making Double-Wall Shells by Centrifuging," Adolphe Tartar (Merck Saint Lievin, France).

Tanks for storing grains or chemicals are often formed from large composite shells. Underground tanks are usually horizontal, and their walls must withstand considerable loads. Wall thickness can be increased, but this is costly and leads to very heavy structures. In this patent, a double-walled shell of fiber-reinforced plastic material of sufficient strength is formed by rotation molding. The outer wall of the shell is first made by forcing glass fibers and liquid resin to the inside face of a cylindrical mold by rotation. Metal strips are applied with moving wheels in a helical arrangement against the outer wall. The space between the turns is filled with resin by rotation. The result is a core of glass-reinforced polyester and metal ridges, giving the shell the necessary rigidity and mechanical strength. The third and last layer is the "top-coat," forming a smooth surface for protection and efficient flow.

Fabricating Filled Materials

U.S. Patent 7,112,267 (September 26, 2006), "Electric-Field Structuring of Composite Materials," Roger W. Whatmore and Steve A. Wilson (Qinetiq Limited, Farnborough, Hants, Britain).

The spatial distribution of a filler within a composite can be controlled by an external electric field if the components have different dielectric permittivities. Polarized filler particles coupled to a moving electrode by dielectrophoretic forces can be dragged into the desired spatial configuration. As the size of the inter-electrode gap is changed, the applied voltage can be adjusted to maintain filler polarization. Piezoelectric composite materials consisting of ferroelectric ceramics in an electrically inactive polymer are examples where the filler distribution affects function. Piezoelectric composites with three-dimensional connectivity are more sensitive but more expensive. However, they are preferred for active devices such as array sensors for acoustic imaging and medical ultrasound. The steps in electric-field fabrication are mixing a nonconducting fluid and a polarizable filler and applying an alternating electric field across two electrodes immersed in the mixture.

Microporous Film

U.S. Patent 7,115,680 (October 3, 2006), "Hydrophilized Porous Film and Process for Producing the Same," Hiroki Fujioka, Hirotoshi Ishizuka, and Takatoshi Sasaki (Nitto Denko Corporation, Osaka, Japan).

Ultrafiltration and microfiltration membranes are used for purification of river water and lake water. However, the durability of separation membranes can be compromised as a result of back-pressure or chemical cleaning. Engineering plastics such as polyvinylidene fluoride, polysulfone, polyethersulfone, polyphenylsulfone, polypropylene, and polyethylene have good chemical resistance and high physical strength, but these polymers are susceptible to fouling because of their hydrophobic character. This patent describes a hydrophilized porous film that can be made with hydrophobic polymers with polar, treated clay. The hydrophilic porous film is formed by casting a hydrophobic polymer solution containing the hydrophilized clay. The film is hydrophilized without impairing rejection and permeation performance. The hydrophobic polymer contains 10- to 30-wt% organized clay. The clay is treated with hydrophilic compounds containing ammonium or phosphonium ions with oxymethylenes, oxyethylenes, or oxypropylenes.

Photopolymerization

U.S. Patent 7,112,616 (September 26, 2006), "Two-Photon--Absorbing Polymerizable Composition and Polymerization Process Thereof," Hiroo Takizawa, Masaharu Akiba, and Takeharu Tani (Fuji Photo Film Co., Ltd., Kanagawa, Japan).

Precise spatial polymerization makes possible three-dimensional memories. An initiator system that enables this precise spatial polymerization consists of a two-photon--absorbing compound, a polymerization initiator, and a polymerizable compound. Methine dyes are two-photon--absorbing compounds in which two photons are simultaneously absorbed. In three-dimensional space, two-photon absorption occurs only in the region having a large electric field strength at the focus where laser rays are converged through a lens. Two-photon absorption does not take place at all in the off-focus region because of weak electric field strengths. Excitation occurs only at a single point inside the space because of the square-law, and therefore, the space resolution is enhanced. Polymerization can be brought about at an arbitrary position in a three-dimensional space, enabling three-dimensional recording. An example consists of a methine dye, an initiator such as ketone (benzophenone) or peroxide (benzoyl peroxide), and an unsaturated monomer. Epoxies and urethane acrylics were polymerized using the two-photon-absorbing initiator systems.

Roger D. Corneliussen is Professor Emeritus of Materials Engineering, Drexel University, in Philadelphia. He is editor of Maro Polymer Alerts and the Maro Polymer website (www.maropolymeronline.com). He has been active in SPE since 1962 and has served on the board of the Philadelphia Section and as National Councilor. For Maro Patent Alerts he reviews all U.S. Patents weekly, makes links to the polymer-related patents, and sends the links daily to subscribers. These patent abstracts in Horizons are based on the weekly selection process. To sample Maro Patent Alerts, email a request to cornelrd@bee.net.
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Title Annotation:Horizons
Author:Corneliussen, Roger D.
Publication:Plastics Engineering
Geographic Code:1USA
Date:Dec 1, 2006
Words:1675
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