Free Radical Addition-fragmentation Research Articles

Copolymerization behaviour of pentadiene-functional macromonomers obtained by free radical addition-fragmentation

Pentadiene-functional macromonomers based on poly (methyl methacrylate) (PMMA) and polystyrene (PS), obtained through a free radical addition-fragmentation reaction were copolymerized with styrene, methyl methacrylate (MMA) and methacrylic acid (MAA) to synthesise well defined graft copolymers. Thus, PMMA-g-PS, PS-g-PMMA and PS-g-PMAA of varying compositions and graft lengths were synthesised. The copolymerization kinetics revealed diminished reactivity of the pentadiene function of the macromonomer towards a given comonomer vis-à-vis the reactivities of the pentadiene monomer or the pentadiene function on the addition-fragmentation agent used to prepare the macromonomers. Methacrylic acid showed apparently reduced reactivity than MMA and the copolymerization of the former with PS-based macromonomer gave amphiphilic graft copolymers with different solubility characteristics. The reactivity of the terminal pentadiene-function of the macromonomer was found to be independent of its molar mass, although its reactivity was marginally diminished in comparison with pentadiene monomer. Low concentrations of high molar mass macromonomer led to the concomitant formation of homopolymers of the small monomer in the case of copolymerization with reactive monomers like MMA and MAA. The graft copolymers have been characterized by chemical methods and by GPC using multiple detectors.

Synthesis of heterotelechelic polymers by free radical addition-fragmentation chain transfer

Telechelic polymers are polymers, generally of moderate molar masses, carrying functional groups at both chain ends. A telechelic polymer is therefore characterized by the nature and the length of the polymer chain and the nature of the functional groups. Classical telechelic polymers are linear macromolecules carrying two identical functional end-groups. When the polymer contains two different functional groups, it is called “heterotelechelic”. During the past decade, a large number of new synthetic methods for the preparation of telechelic polymers have been proposed in the literature. Free radical addition-fragmentation reaction has not only been reported to be a new method allowing chain-length control, because of schematic analogy with chain transfer reaction, but has also been identified as an effective means for generating functional polymers. This review describes new developments in the radical synthesis of heterotelechelic poly(vinyl monomer)s through the use of addition-fragmentation chain transfer agents.

Free radical addition-fragmentation reaction for the preparation of vinyl sulfones and phosphine oxides

Free radical addition-fragmentation reaction for the preparation of vinyl sulfones and phosphine oxides