Poly(5-vinyl-2-norbornene) was synthesised using the nickel bis(acetyl acetonate)/methylaluminoxane (Ni(acac)(2)/MAO) catalytic system. The polymerisation activity is low and depends strongly on temperature. The low reactivity of 5-vinyl-2-norbornene monomer results from both chelating effects and increased steric hindrance of the bulky monomer and the growing chain, which will account for low complexation and insertion rates. Fourier transform infrared spectroscopy (FTIR) characterisation has shown that polymerisation occurred mainly via addition polymerisation of the more strained endocyclic vinylene bond leaving the less strained exocyclic vinyl bond free. (C) 2002 Elsevier Science B.V. All rights reserved.