Synthesis of optically active regioregular poly(thiophene)

A regioregular polythiophene bearing an optically active substituent at the 3-position of thiophene ring, Head-to-Tail poly(3-[2-((S)-1-methyloctyloxy)ethyl]thiophene) (HT-P(S)MOET), was synthesized using highly reactive zinc. HT-P(S)MOET had more than 95% Head-to-Tail coupling with a Mw of 3.72 × 104 (Mw/Mn = 1.20) as estimated by 1H-NMR spectroscopy and gel permeation chromatography. HT-P(S)MOET had strong negative Cotton effect at about 560 and 610 nm and positive Cotton effect at about 490 nm. The presence of circular dichroism effect shows that the chirality of side chains induces the optical activity in poly(thiophene) main chains. The Langmuir-Blodgett films of HT-P(S)MOET exhibited well-defined layer structure and unique optical properties.