Bicyclobutanes and cyclobutenes: Unusual carbocyclic monomers

Bicyclobutanes and cyclobutenes substituted with electron-attracting groups represent novel classes of reactive monomers. They readily undergo free-radical and anionic polymerizations to give high polymers consisting of 1,3- and 1,2-enchained cyclobutane rings, respectively. They also copolymerize readily with conventional vinyl monomers. These polymers display numerous attractive properties in comparison with their vinyl counterparts, including enhanced thermal stability, superior optical properties, and higher glass-transition temperatures. The syntheses of these monomers are reviewed, and suggestions toward future larger scale production are made. (C) 2003 Wiley Periodicals, Inc.