Efficient Free-Radical Cyclopolymerization of Oriented Styrenic Difunctional Monomers

The synthesis of several difunctional monomers, derived from the introduction of two 4-styrene-substituted moieties into a covalent skeleton, is described. The more rigid ones, built around malonate moieties and more preorganized to give 3,3'-cyclophane repeating units, failed completely to give soluble, ordered cyclopolymers. The introduction of a certain degree of flexibility in the tethering moiety afforded, by using free-radical initiation, structurally stable cyclopolymers with a high degree of cyclization and good degrees of polymerization. Theoretical calculations detail and strongly support the experimental results. Further chemical elaboration of the obtained cyclopolymeric backbones, by means of the removal of a ketal group, is possible in mild conditions to give systems which can be easily cross-linked thermally, with the loss of H2O, at temperatures higher than 100 degrees C.