Poly(3-(2-acetoxyethyl)thiophene): A model polymer for acid-catalyzed lithography

Treatment of poly(3-(2-acetoxyethyl)thiophene) (P3AcET) with sulfuric acid simultaneously cleaves the side chain and dopes the polymer backbone. Upon neutralization, the resultant polymer, poly(3-(2-hydroxylethyl)thiophene) (P3HET), is found to be insoluble. Furthermore, the loss of the bulky acetyl group causes a significant red-shift in the absorption spectra as a result of the decrease in intramolecular steric interactions. The hydroxy functionality can be partially reacted to further modify the surface of the film. These phenomena were used to spatially modify the physico-chemical properties of poly(3-alkylthiophene)-based films. Selectively exposure of P3AcET to acid via conventional photolithographic procedures was employed to (i) deposit electronically conducting polymeric patterns, (ii) spatially modify the optical features of films, (iii) spatially modify the surface functionality of films.