Vinyl-Type Addition Polymerization of Norbornene and Synthesis of Norbornene Macromonomers in the Presence of Ethylene Catalyzed by Cobalt(II)−Phosphine Complexes

The polymerization of norbornene (NB) with catalysts obtained by combining cobalt-(II)―phosphine complexes (i.e., CoCl 2 (PR 3 ) 2 , CoCl 2 (PRPh 2 ) 2 , R = alkyl or cycloalkyl group, Ph ― phenyl) with methylaluminoxane (MAO) is reported. These systems exhibited excellent activity when used in an halohydrocarbon solvent, yielding amorphous, soluble vinyl-type poly(norbornene)s (PNB)s. The NB copolymerization with ethylene (E) was also examined. Norbornene macromonomers (M n in the range 740—8740 g mol ―1 ) with a terminal vinyl group, likely originating from insertion of one ethylene molecule followed by a β-hydrogen elimination reaction, were obtained in almost 100% yield. By varying the NB starting concentration as well as the time and the polymerization temperature, it was possible to tune the molecular weight of the macromonomers which exhibited different T g values upon the NB polymerization degree. The PNBs and the macromonomers were fully characterized by NMR analysis, and a reaction mechanism for the formation of the vinyl-end NB macromonomers in the copolymerization of NB with E is proposed.