Formation of trans-Poly(thienylenevinylene) Thin Films by Solid-State Thermal Isomerization

Cis-to-trans isomerization of poly­(thienylenevinylene) is found to be a viable fabrication method for semiconducting trans-poly­(thienylenevinylene) (trans-P1) thin films. Specifically, thin films of trans-P1, an alternating copolymer containing isoindigo and (E)-1,2-dithienylethene units, which are well known as an excellent p-type semiconductor, were prepared by thermally annealing thin films of the cis-poly­(thienylenevinylene) (cis-P1) isomer (92% cis) at 240 °C for 30 min. The hole mobility of the isomerized films is comparable to that of films prepared from spin-coated solutions of the trans-isomer. Taking advantage of the greater solubility of the cis-isomer, it was possible to replace the toxic halogenated solvents normally needed for the dissolution of trans-P1 with the environmentally friendly 2-MeTHF. Solid-state cis-to-trans isomerization is therefore a potentially attractive fabrication option for the commercial development of sustainable, printable electronics.