Synthesis and spectroscopic and electrochemical characterisation of a conducting polythiophene bearing a chiral beta-substituent: Polymerisation of (+)-4,4 '-bis[(S)-2-methylbutylsulfanyl]-2,2 '-bithiophene

A regioregular head-to-head/tail-to-tail poly(beta,beta'-disubstituted bith iophene) P1 was synthesised by chemical and electrochemical polymerisation of 2,2'-bithiophene that bears (S)-2-methylbutylsulfanyl chains in the beta and beta'-positions. The polymer was characterised by GPC, NMR and UV/Vis spectroscopy, CD, AFM and by electrochemical and conductivity measurements. The CD spectra of P1 in solutions in which poor solvents are present show interesting features and allow the presence of different optically active s pecies to be distinguished. Upon varying the casting conditions of P1, diff erent relative amounts of grainy and homogeneous aggregated phases were obs erved in AFM micrographies of films and corresponding negative or positive first Cotton effects were found in the CD spectra. AFM, CD and UV/Vis chara cterisations were also performed on an electrogenerated optically active po lymer PE1. in order to make a comparison with the chemically synthesised on e. The interesting, small band gap of P1 allows for easy p- and n-electroch emical doping.