Fluorene and silafluorene conjugated copolymer: A new blue light-emitting polymer

A novel series of soluble blue light-emitting conjugated random and alternating copolymers derived from 9,9′-dioctylfluorene (FO) and 3,6-dimethoxyl-9,9-dimethyl-9-silafluorene (DMSiF) were successfully synthesized by Suzuki coupling polymerization. The feed ratios of FO to DMSiF were 90:10, 80:20, 75:25, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by NMR, UV absorption, photoluminescence, and cyclic voltammetry. The 1H NMR spactra of the copolymers indicated that DMSiF content in the copolymers was slightly lower than its feed composition. The random copolymers exhibited PFO-segment-dominated UV absorption and PL spectra in THF solution, in comparison with significantly blue-shifted spectra of the alternating copolymer. The blue shift of the spectra became more remarkable in cast film and increased with the increment of DMSiF content. The changes of the UV absorption and PL spectra in solution and film were ascribed to the effect of methoxyl substituents which can hinder the chain rotation and influence the polymer comformation espercially in the solid film. The systematic invesetigations on the solubility, thermostability, electrochemical property, and photophysical property of the copolymers showed that silafluorene was an attractive building unit for optoelectronic materials.