Selective Reaction of Exo-Isomers in Ring-Opening Olefin Metathesis Polymerization (ROMP) of Fluoroalkyl-Substituted Norbornene Derivatives

Abstract

Fluoroalkyl-substituted bicyclic and tricyclic olefins were polymerized by ring-opening olefin metathesis polymerization (ROMP). The monomers used were mixtures of exo- and endo-isomers of 5,5,6-trifluoro-6-(trifluoromethyl)spiro(bicyclo[2.2.1]hept-2-ene-7,1′-cyclopropane),5,6-difluoro-5-(trifluoromethyl)-6-(heptafiuoroisopropyl)bicyclo[2.2.1]hept-2-ene, and 2,3,3,4,4,5,5,6-octafluorotricyclo[2.2.1]hept-2-ene obtained by the Diels–Alder reaction of cyclopentadiene and spiro[2.4]hepta-4,6-diene with perfluorinated olefins. The polymerization reactions were carried out with a conventional catalyst based on tungsten hexachloride. The exo-isomers were found to be more reactive than the corresponding endo-isomers. This difference in reactivity was larger for monomers containing more voluminous substituents. A model based on steric repulsion is proposed to describe the selectivity for polymerization of the exo-isomers. © 1993, American Chemical Society. All rights reserved.