Copolymers of one or more halogenated olefins and one or more halogenated co-monomers selected from the group consisting of halogenated alkenyl ethers, halogenated alkenyl esters, and halogenated (meth)acrylates are useful in various end-use applications wherein the presence of halogen (e.g., fluorine) in the copolymer imparts one or more desirable properties, as compared to analogous copolymers not containing halogen.

Described herein is method of making branched perfluorinated compounds, specifically (CF.sub.3).sub.2CFCF(CF.sub.3)OCF(CF.sub.3)C(═O)F and (CF.sub.3).sub.2CFCF(CF.sub.3)OCF═CF.sub.2. Also disclosed herein is a fluoropolymer derived from the branched perfluorovinyl ether monomer and methods of making the fluoropolymer.

Copolymers of one or more halogenated olefins and one or more halogenated co-monomers selected from the group consisting of halogenated alkenyl ethers, halogenated alkenyl esters, and halogenated (meth)acrylates are useful in various end-use applications wherein the presence of halogen (e.g., fluorine) in the copolymer imparts one or more desirable properties, as compared to analogous copolymers not containing halogen.

A method for producing a fluoropolymer, which includes: polymerizing a monomer (I) represented by the general formula (I) below in an aqueous medium substantially in the absence of a fluorine-containing surfactant (except for the monomer (I) represented by the general formula (I)) to obtain a crude composition containing a polymer of the monomer (I); removing a dimer and a trimer of the monomer (I) contained in the crude composition from the crude composition to obtain a polymer (I) in which the content of the dimer and trimer of the monomer (I) is 1.0% by mass or less based on the polymer (I); and polymerizing a fluoromonomer in an aqueous medium in the presence of the polymer (I) to obtain a fluoropolymer:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m  (I)

wherein X.sup.1 and X.sup.3, X.sup.2, A.sup.0, R, Z.sup.1 and Z.sup.2 are as defined herein.

A method for producing a fluoropolymer, which includes: polymerizing a monomer (I) represented by the general formula (I) below in an aqueous medium substantially in the absence of a fluorine-containing surfactant (except for the monomer (I) represented by the general formula (I)) to obtain a crude composition containing a polymer of the monomer (I); removing a dimer and a trimer of the monomer (I) contained in the crude composition from the crude composition to obtain a polymer (I) in which the content of the dimer and trimer of the monomer (I) is 1.0% by mass or less based on the polymer (I); and polymerizing a fluoromonomer in an aqueous medium in the presence of the polymer (I) to obtain a fluoropolymer:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m  (I)

wherein X.sup.1 and X.sup.3, X.sup.2, A.sup.0, R, Z.sup.1 and Z.sup.2 are as defined herein.

Described herein is method of making branched perfluorinated compounds, specifically (CF.sub.3).sub.2CFCF(CF.sub.3)OCF(CF.sub.3)C(═O)F and (CF.sub.3).sub.2CFCF(CF.sub.3)OCF═CF.sub.2. Also disclosed herein is a fluoropolymer derived from the branched perfluorovinyl ether monomer and methods of making the fluoropolymer.

Copolymers of one or more halogenated olefins and one or more halogenated co-monomers selected from the group consisting of halogenated alkenyl ethers, halogenated alkenyl esters, and halogenated (meth)acrylates are useful in various end-use applications wherein the presence of halogen (e.g., fluorine) in the copolymer imparts one or more desirable properties, as compared to analogous copolymers not containing halogen.

Composite membranes comprised of at least two layers, one of the layers being a silver ionomer and a second layer which is a fluorinated polymer with certain permeability properties, are especially useful for the separation of alkanes from alkenes, Particularly useful is a three-layer composite membrane in which a porous layer is laminated to the second layer.

Presently described are electronic telecommunication articles comprising core shell fluoropolymers comprising polymerized units of tetrafluoroethylene and no greater than 1 wt. % of polymerized units of comonomer comprising a functional group. The functional groups are typically selected from nitrile, halogen, sulfur oxide, perfluorinated alkyl ether, and carbonyl. The core shell fluoropolymer typically comprises at least 80, 85, 90, 95, 96, 97, 98, 99 wt. % or greater of polymerized units of tetrafluoroethylene. In some embodiments, the core shell fluoropolymer further comprises up to 20 or 25 wt. % of polymerized units of other comonomers, such as hexafluoropropylene (HFP). Also described are methods of making a coated substrate, coated substrates, and core shell fluoropolymers.

Composite membranes comprised of at least two layers, one of the layers being a silver ionomer and a second layer which is a fluorinated polymer with certain permeability properties, are especially useful for the separation of alkanes from alkenes, Particularly useful is a three-layer composite membrane in which a porous layer is laminated to the second layer.