Synthesis and property studies of linear and kinked poly(pyreneethynylene)s

A series of fluorescent conjugated polymers, poly(pyreneethynylene)s, have been designed and synthesized to investigate the effect of shape of polymer backbone on physical properties. Polymers with linear and kinked backbone were synthesized using 1,6- and 1,8-disubstituted pyrene. The target copolymers were designed to incorporate various spacer units, such as, alkoxyphenyl, carbazole and fluorene on the polymer backbone. Characterization of the target compounds was achieved by NMR, IR, GPC and MALDI-TOF mass spectrometry. Detailed investigation on their optical, electrochemical and thermal properties revealed significant contribution of the geometry of polymer backbone towards physical properties. Kinked backbone of cisoid-polymers was found to result in lower optical band gap, less negative EHOMO and higher thermal stability as compared to their linear analogues, most probably due to the coiling of polymer chains. Comparison of the physical properties of the polymers with those of the model compounds suggested similar extent of conjugation through 1,6- and 1,8-position of pyrene.