Synthesis and characterisation of telechelic regioregular head-to-tail poly(3-alkylthiophenes)

An investigation into the Stille cross-coupling reaction as an alternative synthetic route to regioregular head-to-tail poly(3-alkylthiophenes) is presented. 2-Iodo-3-alkyl-5-tri-n-butylstannylthiophene derivatives were made, isolated and characterised and subsequently used in Pd-0 catalysed cross-coupling reactions in different solvents. Short and long chain regioregular poly(3-hexylthiophenes) with over 96% head-to-tail coupling ratios between adjacent thiophene rings were obtained. The materials were analysed by gel permeation chromatography and NMR spectroscopy. Polymers with varying degrees of polymerisation were obtained depending on the conditions used. End group analysis has shown that polymers, functionalised with both iodo and tri-n-butyltin end groups can be obtained under certain reaction conditions. Preliminary homocoupling reactions were also conducted.