François Isel

Pyridine bis(imine) cobalt or iron complexes for ethylene and 1-hexene (co)polymerisation

Brookhart and Gibson have recently described the synthesis of new iron and cobalt complexes with pyridine bis(imine) ligands for the polymerisation of ethylene and propylene. In the present paper, the synthesis of new complexes modified with heteroatoms, based on the above-mentioned catalysts, is reported. Higher activities are observed. The influence of the polymerisation temperature on the catalytic activity has been investigated. The first example of the successful copolymerisation of ethylene and 1-hexene with these catalysts is also discussed. The (co)polymers have been characterized by high temperature 13C NMR. To cite this article: R. Souane et al., C. R. Chimie 5 (2002) 43–48

Macromonomers as well-defined building blocks in macromolecular engineering

The present work compares the efficiency of different polymerization methods to design well-defined comb-shaped structures based on macromonomers. Anionic polymerization remains the method of choice and allows the control of polymerization degree of the main chain and the length of the grafts. The presence of an active chain end on the backbone enabled the synthesis of a new type of hyperbranched polymers by reaction, with appropriate low molar multifunctional compounds. Free radical polymerization is less efficient for the controlled homopolymerization of macromonomers but less sensitive to the presence of impurities. It requires in most cases long fractionation procedures to access well defined comb-shaped fractions characterized by high molar masses. The controlled free radical polymerization constitutes an interesting alternative. The homopolymerization of macromonomers with late transition metal catalysts was also examined and comb-shaped polymers characterized by a syndiotactic backbone and atactic grafts could be obtained.