synopsisPolymerization of (E,E &[6.2]paracyclophane-l,5diene proceeds by an intra-intermolecular mechanism to give a polymer containing a [3.2]paracyclophane in the repeat unit. Polymerization occurs with either free radical or cationic initiation; anionic initiation was unsuccessful. Cationic polymerization is favored and appears to proceed through a stabilized carbonium ion intermediate. Spectroscopic and model compound studies are consistent with the proposed polymer structure. Thermal analyses of the polymer indicate a complex thermooxidative behavior in the presence of oxygen, while depolymerization occurs above about 4WC in an inert atmosphere.It appeared likely that cyclopolymerization leading to such [3.2]paracyclophane units would be favored in a 1,2-bis(p-vinylphenylkthane structure if the vinyl groups were constrained to lie in close proximity. This proves to be the case. In this paper we describe the ~y n t h e s i s ,~ characterization and properties of cyclopolymer 6 derived from (E,E)-[6.2] paracyclophane-l,5diene (5 1.