In this paper we report on the in-situ polymerization of 3T with Cu(ClO4)2 inside several host polymers such as novolak-based negative-tone photoresist, polystyrene (PS), poly(4-vinylphenol) (P4VP) polymethylmethacrylate (PMMA) and poly(4-vinylphenol)-co-(methylmethacrylate) P4VP-co-MMA to form an interpenetrating polymer network (IPN). Conducting IPN films in the order of 10-4 to 150 S/cm are obtained depending on the specific IPN composition. Moreover, the convenience of this synthetic approach has been demonstrated using a commercially available negative-tone photoresist based on novolak as a host polymer. Novolak photoresist was properly formulated with 3T and Cu(ClO4)2 to preserve as far as possible the negative lithographic characteristics of novolak-based photoresist and generate conductive micropatterns by means of UV lithography. The CP is in-situ synthesized into the novolak matrix by a post-bake after the lithography process (exposure + development). The electrical conductivity of the patterned film is 10-2 S/cm. We accurately patterned three different types of microstructures with different resolutions: interdigitated structures with a width of 100 µm, 200 µm-side squares and a 20 µm-wide cross. We believe this synthetic approach is of potential application to modify the conductivity of numerous insulating polymers while preserving their physical and chemical properties.