In-situ synthesis of thiophene-based multifunctional polymeric networks with tunable conductivity and high photolithographic performance

Design of novel multifunctional polymeric materials combining electrically conducting properties with patterning capability is a significant challenge in materials science. Herein, we report on the synthesis of multifunctional interpenetrating polymer networks (IPN) by the in-situ oxidative polymerization of thiophene-based monomers with Cu(ClO4)2 inside a novolac-based photoresist. The resulting IPNs show conductivities up to 20 S/cm depending on the monomer properties. Among them, 3,3‴-Dihexyl-2,2’:5′,2’’:5″,2‴-quaterthiophene (DH4T) is chosen because it has the largest conjugation length and excellent solubility in organic solvents. Moreover, it renders a low percolation threshold and smooth surface morphology if compared with terthiophene (3T). FTIR and XPS spectroscopy confirm the DH4T polymerization by Cu(ClO4)2 and provide some insights about the doping level of the conducting polymer. We also propose a new photolithographic route based on the DH4T polymerization in novolac after pattern generation by oxidant sorption. This novel fabrication route leads to conducting IPNs with outstanding lithographic performance. [Display omitted] •The oxidative polymerization of thiophene derivatives inside novolac is demonstrated.•The resulting IPNs show conductivities up to 20 S/cm depending on the monomer.•DH4T-based IPN films exhibit low percolation threshold and good film morphology.•DH4T in-situ polymerization reaction is highly temperature dependent.•A novel fabrication route to DH4T-based conducting micropatterns is presented.