Ring opening metathesis polymerisation of n-alkyl norbornene dicarboxyimides using well-defined initiators

Exo-n-alkyl norbornene dicarboxyimides and endo-n-octyl norbornene dicarboxyimide were polymerised by ring opening metathesis polymerisation using well-defined initiators Mo(CH-t-Bu)(NAr)(OCMe3)(2) and Mo(CHCPh-Me-2)(NAT)(OCMe(CF3)(2))(2). Using Mo(CH-t-Bu)(NAr)(OCMe3)(2) and Mo(CHCPhMe2)(NAr)(OCMe(CF3)(2))(2) as initiators with the exo-monomers gave polymers with 97% trans and 70% cis vinylene content, respectively, and with the endo-monomer gave polymers with 93% trans and 57% trans vinylene content. In both cases the C-13 n.m.r. spectra were complex indicating that these polymers are essentially atactic. H-1 n.m.r. Spectroscopy and GPC analyses of polymeric materials prepared from exo- and endo-monomers demonstrated that the initiator carrying t-butoxy ligands gives fairly well-defined living polymerisation; whereas with the initiator bearing fluorinated ligands propagation is significantly faster than initiation which leads to much higher molecular weights than expected on the basis of monomer to initiator ratio and a broadening of the molecular weight distribution. The living character of these systems was confirmed by the synthesis of AB diblock copolymers via sequential addition of monomers. A series of block copolymers were prepared using exo-n-alkyl norbornene dicarboxyimides as monomer and 7,3-bis(trifluoromethyl)norbornadiene as comonomer. The glass transition temperatures of the polymers obtained from endo-monomers are significantly higher than those of the poly(exo-n-alkyl norbornene dicarboxyimide)s, probably as a consequence of a stiffer less mobile backbone resulting from the endo repeat units. (C) 1998 Elsevier Science Ltd. All rights reserved.