Telomerization

Abstract: After an introduction reporting the properties and the applications of fluoropolymers, a first part deals with i) the main routes to produce chlorotrifluoroethylene (CTFE) monomer, ii) its telomerization reaction involving various chain transfer agents, iii) its homopolymerization, and iv) the advantages and uses of (PCTFE). In a second section, this review, illustrated by numerous examples, extensively reports the synthesis, properties and applications of the copolymers based on CTFE with non-halogenated, fluorinated, commercially available or synthesized comonomers. These comonomers exhibit XYC=CZ-Sp-R structures where X, Y, and Z represent H, F, and CF3 groups, Sp a spacer and R an alkyl group, a halogen atom or a function such as OH, OAc, SAc, CO2R' (R' being a H atom or an alkyl group), and SO3H. According to the nature and to the amount of the comonomer, the copolymers can be thermoplastic, elastomeric or thermoplastic elastomers. Introducing reactive R side groups brings complementary properties such as solubility, hydrophily, ionic exchange or surface properties, or further crosslinking of the resulting copolymers. Then, the kinetics of radical copolymerization of CTFE with M comonomers led to the assessment of the reactivity ratios which are compared. Hence, a reactivity series of these M comonomers with respect to a macroradical terminated by CTFE is proposed. Usually, these copolymers exhibit random structures except with vinyl ethers that produced alternating copolymers with CTFE. The controlled radical copolymerizations of CTFE with other comonomers (such as vinylidene fluoride or vinyl ether) either in the presence of borinates or iodo-compounds are also reported. In addition, new CTFE-containing copolymers exhibit well-defined architectures, such as telechelic, alternating, block and graft copolymers. They can be synthesized either by conventional techniques (i.e. telomerisation) or by controlled radical copolymerization. Chemical modifications of PCTFE and poly(CTFE-co-monomer) copolymers are also presented. Several properties and applications (such as surfactants, optical fibres, polymer electrolytes for lithium ion batteries, dielectrical polymers, thermoplastic elastomers, fuel cell and ultrafiltration membranes) of these CTFE containing copolymers also illustrate this review.

Abstract: In order to make polyacrylonitrile (PAN) fluidic, acrylonitrile telomer (ANT) is synthesized by radical telomerization and used as a nitrogen and carbon precursor to prepare a non-noble oxygen reduction reaction (ORR) catalyst. This fluidic precursor greatly increases the contact between Fe salt aggregates and the polymer so that more active sites are formed during stabilization and carbonization. Such prepared catalysts and the commercial Pt/C catalyst have comparable ORR performance and stability.