Use of telechelic fluorinated diiodides to obtain well-defined fluoropolymers

Different methods of synthesis involved in the preparation of fluorinated telechelics (or alpha,w-difunctional compounds) from alpha,w-diiodoperfluoroalkanes for obtaining well-defined fluoropolymers are described. This review focuses on molecules in which fluorinated chains are located on the backbone and not in a lateral position. First, a bibliographical approach develops the syntheses of alpha,w-diiodoperfluoroalkanes (1) either by chemical transformations of telechelic derivatives or by telomerisation of fluoroolefins with molecular iodine or diiodoperfluoroalkanes. Then, fluorotelechelics are synthesised by means of four different processes: (a) by the chemical change in the presence of metalic salts: Cb) from the bismonoaddition of 1 to w-functional unsaturated derivatives; (c) from the bis(monoethylenation) of 1 followed by difunctionalisation (e.g., nucleophilic substitution); (d) from the coupling reactions between 1 and alpha-iodo-w-functional reactants. Finally, this review describes how several well-defined fluoropolymers can be produced from these fluorinated telechelics. Their specific chemical, physical and thermal properties are discussed with regard to modern industrial requirements. (C) 1999 Elsevier Science S.A. All rights reserved.