Synthesis, orientation and optical properties of thiophene–dialkoxyphenylene copolymers

A (thienylene–dialkoxyphenylene) copolymer has been prepared by using an organometallic condensation reaction between a bis(stannyl)thiophene reagent and a substituted dibromobenzene derivative in the presence of a palladium catalyst. The grafting of 2-butoxyethoxy substituents gave the polymer a good solubility in most organic solvents. Moreover, owing to the presence of polar dialkoxy chains along the conjugated skeleton, a material with excellent glass adhesion properties was obtained. It allows the formation of homogeneous thin films coatings. The material is highly fluorescent (Φsol = 0.9, λsol = 520 nm). The polymer was ordered by coating on an oriented Teflon deposit on a glass support and exhibited polarized fluorescence. On the other hand, the material presented a stable reversible blue–red electrochromism associated with a redox transfer at a low potential value (0.5 V vs. SCE). Moreover, the electrochromic properties of this material are preserved even in an aqueous electrolytic medium (LiClO4–H2O). The copolymer with enhanced optical properties compares quite favorably to polythiophene and has good potential for the elaboration of optical devices; for example it seems to be a good candidate for the preparation of electroluminescent diodes with polarized emission.