Cycloaddition polymerization

The synthesis of macromolecules by utilizing the 1.3‐ and 1.4‐cycloadditions as the polymer‐forming reaction can provide totally aromatic thermally stable materials. Of the 1.3‐dipole cycloadditions, the reaction of the tetrazoles with dipolarophiles is the best suited synthesis and yields high molecular weight materials containing pyrazole or triazole rings in the chain. This reaction has also been employed to crosslink already formed polymers. The D IELS ‐A LDER reaction of cyclopentadienones or α‐pyrones with acetylene dienophiles provides a unique and unequivocal method of synthesis of polyphenylenes. High molecular weight phenylated polyphenylenes and poly( p ‐phenylene) can be obtained from this reaction. Whereas the phenylated polyphenylenes are amorphous and soluble in common organic solvents, poly( p ‐phenylene) is highly crystalline and insoluble in all solvents. Both types of polymers are light yellow and thermally stable.