Click Polymerization:  Facile Synthesis of Functional Poly(aroyltriazole)s by Metal-Free, Regioselective 1,3-Dipolar Polycycloaddition

Heating mixtures of bis(aroylacetylene)s (5/6/9) and diazides (7/8) in polar solvents such as DMF/toluene at a moderate temperature of 100°C readily affects their 1,3-dipolar polycycloadditions, producing poly-(aroyltriazole)s (PATAs; PI-PXII) with high molecular weights (M _w up to 26 700) and regioregularities (F_1,4 up to ∼92%) in high yields (up to ∼98%). The metal-free click polymerizations propagate smoothly in an open atmosphere without protection from oxygen and moisture. Through model reaction study and semiempirical calculation, the polymerization mechanism is proposed and discussed. Molecular structures of the PATAs are characterized spectroscopically. All the polymers are soluble in common organic solvents and are thermally stable, losing little of their weights when heated to ∼380°C. The PATAs containing triphenylamine units emit visible light and show unique solvatochromism. The PATAs are nonlinear optically active, exhibiting large two-photon absorption cross sections due to the intramolecular charge transfer between their electron-donating triphenylamine and electron-accepting aroyltriazole units.