Surface Grafting of Functionalized Poly(thiophene)s Using Thiol-Ene Click Chemistry for Thin Film Stabilization

Regioregular poly[(3-hexylthiophene)-ran-(3-undecenylthiophene)] (pP3HT) and vinyl terminated poly(3-hexylthiophene) (xP3HT) were synthesized by the McCullough method and surface grafted to thiol modified silicon dioxide wafers using thiol-ene click chemistry. Utilizing this method, semiconducting, solvent impervious films were easily generated. Thiol-ene click chemistry is convenient for film stabilization in electronics because it does not produce side products that could be inimical to charge transport in the active layer. It was found through grazing incidence wide-angle X-ray scattering (GIWAXS) that there is no change in microstructure between as-spun films and thiol-ene grafted films, while there was a change after the thiol-ene grafted film was exposed to solvent. Organic field-effect transistors (oFETs) were fabricated from grafted films that had been swelled with chloroform, and these devices had mobilities on the order of 10^-6 cm² V^-1 s^-1, which are consistent with poly(thiophene) monolayer devices.