A new series of catalysts based on ruthenium alkylidene complexes has been developed by R Grubbs¹ (a recent Nobel Laureate in Chemistry). One aspect of these catalysts is the ability to perform ring opening metathesis polymerization, which transforms ring compounds with vinyl groups into polymers. For example 1, 4 cyclo-octadiene can be ring opened to form polybutadiene (BR), an elastomer. In our work we have also polymerised norbornene which leads to a stiffer polymer.

An attractive aspect of the work is that several catalysts can be purchased and can be rather stable. Reactions take on 'click chemistry' attributes: they are rapid, selective and can be done in environments such as water which are often detrimental to other complexes such as Zeigler Natta and metallocene catalysts. Homopolymers of COD and NBE have been prepared in 95% yields with molecular weights ranging from 33,000 to 94,000 and polydispersities of 2.

The click nature of these ROMP catalysts allows the formation of polybutadiene in the presence of polystyrene, to form blends in which the rubbery part is dispersed differently to conventional high impact polystyrene polymers. In the latter case, it is normal for the BR, which has been made from water and air sensitive catalysts, to be made first and then dissolved in styrene monomer. This is typically bulk polymerised using free radical catalysts whereupon a phase inversion occurs leading to dispersed 'bubbles' of rubber which act as craze arresters and so toughen the plastic².

Here for the first time we have made an entirely different blend, as the BR is formed in the presence of the polystyrene. Some initial morphological EM data of these new blends will be presented.

1 R H Grubbs, Handbook of Metathesis, Wiley VCH, 2003
2 J Scheirs and D Priddy, Modern Styrenic Polymers, Wiley, 2003