To elucidate the application range of the protocol, four types
of dibromoarylenes were examined as monomers in the polycondensation
(Scheme 2). To confirm the effect of microwave
heating, the polycondensation reactions under conventional
heating were conducted as control experiments. Table 2 summarizes
the results. The structures of the obtained polymers
were confirmed by NMR spectroscopy; detailed characterization
of the polymers is summarized in the experimental section
and Supporting Information. The results revealed that
microwave heating yields several poly(arylamine)s with comparable
or higher molecular weights as compared to those
obtained using conventional heating. Therefore, the shortened
reaction time and reduced catalyst loading are considered to
be prominent features of the reaction carried out under
microwave heating. Alternatively, in the case of Polymer 4,
the reaction under microwave heating afforded a fraction that
was insoluble in chloroform; the extraction of the chloroform
soluble fraction resulted in a low yield presumably due to
the low solubility of the high-molecular-weight polymer.