Abstract: A composite membrane for use in a fuel cell membrane electrode assembly comprises a porous polymeric substrate and an impregnant partially filling the substrate such that the substrate comprises a first region having pores substantially filled with the impregnant, and a second substantially porous region. The impregnant comprises a cation exchange material. The cation exchange material covers one surface of the substrate in a dense surface layer, contiguous with the first region of the substrate. The substrate has greater than 10% residual porosity, and the composite membrane is substantially gas impermeable and has at least one substantially porous major surface.

Abstract: A process for preparing a graft copolymer membrane is provided comprising exposing a polymeric base film to a dose of ionizing radiation, and then contacting the irradiated base film with an emulsion comprising a fluorostyrenic monomer.

Abstract: A process for preparing a graft copolymer membrane is provided comprising exposing a porous polymeric base film to a dose of ionizing radiation, and then contacting the irradiated base film with an emulsion comprising a fluorostyrenic or fluoronaphthyl monomer. The graft copolymer membrane may be densified to render it substantially gas-impermeable.

Abstract: &agr;,&bgr;,&bgr;-Trifluorostyrene and derivatives thereof synthesized in two steps from 1,1,1,2-tetrafluoroethylene. In the first step, 1,1,1,2-tetrafluoroethylene is reacted with a base, a metal salt such as zinc chloride and an optionally amine to form a trifluorovinyl metal complex. In the second step, the trifluorostyrene or derivative is obtained by reacting the trifluorovinyl metal complex with an aryl transfer agent such as, for example, an aryl triflate or an aryl halide, in the presence of a metal catalyst and optionally a coordinating ligand. Both steps may be carried out in one reactor.

Abstract: A precision oven-controlled crystal oscillator (OCXO) uses an adjustment feedback signal that, when mixed with a reference signal from a stable reference oscillator, accurately controls the generation of an output signal from a voltage controlled crystal oscillator (VCXO). An OCXO according to the invention has high stability and high accuracy. The digital OXCO can be manufactured at low cost, and is particularly beneficial for Code Division Multiple Access (CDMA) base station applications in cellular communication networks an the like.

Abstract: &agr;,&bgr;,&bgr;-Trifluorostyrene and derivatives thereof synthesized in two steps from 1,1,1,2-tetrafluoroethylene. In the first step, 1,1,1,2-tetrafluoroethylene is reacted with a base, a metal salt such as zinc chloride and an optionally amine to form a trifluorovinyl metal complex. In the second step, the trifluorostyrene or derivative is obtained by reacting the trifluorovinyl metal complex with an aryl transfer agent such as, for example, an aryl triflate or an aryl halide, in the presence of a metal catalyst and optionally a coordinating ligand. Both steps may be carried out in one reactor.

Abstract: A precision oven-controlled crystal oscillator (OCXO) uses an adjustment feedback signal that, when mixed with a reference signal from a stable reference oscillator, accurately controls the generation of an output signal from a voltage controlled crystal oscillator (VCXO). An OCXO according to the invention has high stability and high accuracy. The digital OXCO can be manufactured at low cost, and is particularly beneficial for Code Division Multiple Access (CDMA) base station applications in cellular communication networks an the like.

Abstract: Ion-exchange materials comprising a polymeric backbone and a plurality of pendent styrenic or fluorinated styrenic macromonomers covalently bonded thereto, wherein the plurality of pendent styrenic or fluorinated styrenic macromonomers comprise a uniform number of styrenic or fluorinated styrenic monomer repeat units, and wherein predominantly all of the styrenic or fluorinated styrenic monomer repeat units have at least one charged group. Processes for making such materials, as well as products related thereto, are also disclosed. In a representative embodiment, the ion-exchange material is utilized as a proton-exchange membrane (PEM) for use in a PEM fuel cell.

Abstract: A composite membrane for use in a fuel cell membrane electrode assembly comprises a porous polymeric substrate and an impregnant partially filling the substrate such that the substrate comprises a first region having pores substantially filled with the impregnant, and a second substantially porous region. The impregnant comprises a cation exchange material. The cation exchange material covers one surface of the substrate in a dense surface layer, contiguous with the first region of the substrate. The substrate has greater than 10% residual porosity, and the composite membrane is substantially gas impermeable and has at least one substantially porous major surface.

Abstract: Stripped porous polymer film and a method for making such film from substantially heterogeneous porous polymer film are described. The heterogeneous film has surface characteristics that are different from the characteristics of the interior bulk material, and the method comprises mechanically stripping at least a portion of at least one surface layer from the heterogeneous film. The stripped porous polymer film may be incorporated into composite membranes. Such composite membranes are particularly suitable for incorporation into membrane electrode assemblies for use in electrochemical cells, including electrochemical fuel cells.

Abstract: A membrane electrode assembly comprises first and second electrodes and a composite membrane interposed therebetween. The composite membrane comprises a porous substrate impregnated with a polymeric composition comprising polymerized &agr;,&bgr;,&bgr;-trifluorostyrene monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant membrane electrode assembly is useful in electrochemical applications, particularly as a membrane electrode assembly in electrochemical fuel cells.

Abstract: Graft polymeric membranes and methods for making graft polymeric membranes have one or more trifluorovinyl aromatic monomers that are radiation graft polymerized to a polymeric base film. The membranes comprise a polymeric base film to which has been graft polymerized substituted &agr;,&agr;,&bgr;-trifluorostyrene and/or &agr;,&agr;,&bgr;-trifluorovinylnaphthylene monomers, which are activated towards graft polymerization. As ion-exchange membranes, the membranes are suitable for use in electrode apparatus, including membrane electrode assemblies in, for example, fuel cells. The membranes can also be crosslinked.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of &agr;,&bgr;,&bgr;-trifluorostyrene, substituted &agr;,&bgr;,&bgr;-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.

Abstract: A precision oven-controlled crystal oscillator (OCXO) uses an adjustment feedback signal that, when mixed with a reference signal from a stable reference oscillator, accurately controls the generation of an output signal from a voltage controlled crystal oscillator (VCXO). An OCXO according to the invention has high stability and high accuracy. The digital OXCO can be manufactured at low cost, and is particularly beneficial for Code Division Multiple Access (CDMA) base station applications in cellular communication networks an the like.

Abstract: Stripped porous polymer film and a method for making such film from substantially heterogeneous porous polymer film are described. The heterogeneous film has surface characteristics that are different from the characteristics of the interior bulk material, and the method comprises mechanically stripping at least a portion of at least one surface layer from the heterogeneous film. The stripped porous polymer film may be incorporated into composite membranes. Such composite membranes are particularly suitable for incorporation into membrane electrode assemblies for use in electrochemical cells, including electrochemical fuel cells.

Abstract: Graft polymeric membranes in which one or more trifluorovinyl aromatic monomers are radiation graft polymerized to a preformed polymeric base film are provided, as well as ion-exchange membranes prepared therefrom. Preferred monomers include substituted &agr;, &bgr;, &bgr;-trifluorostyrenes and trifluorovinyl naphthalenes which are activated towards the grafting reaction or facilitate the introduction of more than one ion-exchange group per monomer unit in the grafted chains. The ion-exchange membranes are useful in dialysis applications, and particularly in electrochemical applications, for example as membrane electrolytes in electrochemical fuel cells and electrolyzers.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of &agr;,&bgr;,&bgr;-trifluorostyrene, substituted &agr;,&bgr;,&bgr;-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of &agr;, &bgr;, &bgr;-trifluorostyrene, substituted &agr;, &bgr;, &bgr;-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of .alpha.,.beta.,.beta.-trifluorostyrene, substituted .alpha.,.beta.,.beta.-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of .alpha.,.beta.,.beta.-trifluorostyrene, substituted .alpha.,.beta.,.beta.-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.