Polymerization behaviour of biscarbenes derived by thermolysis of bisdiazo compounds†

Abstract

A study of the collapse of bisdiazo compounds with different terminal groups upon heating to generate reactive biscarbene intermediates has provided evidence for homopolymerization in a process that proceeds in the absence of catalysts and is tolerant of oxygen. This polymerization behaviour was monitored spectroscopically through UV-vis kinetic analysis with various combinations of temperature and solvent, and clear evidence for dimer and trimer formation was found by field desorption mass spectrometry. Oligomerization may involve the formation of CC and CN–NC linkages, as studied and validated by molecular dynamics (MD) calculations, before reaching macromolecular size. In the presence of terminal NH₂ groups, cross-linking resulting from carbene insertion is also observed. This unusual polymerization of diazo monomers, when conducted on a polyvinyl alcohol (PVA) surface in the open-air upon heating, creates a highly cross-linked structure that changes surface properties.