A linear aniline-formaldehyde resin (AF) complexed with different acids was successfully synthesized with the traditional way of polymerizing a novolac-type phenolic resin. When the AF(DBSA)(1.0) (AF complexed with only HDBSA (n-dodecyl benzene sulfonic acid)) was blended with PANI(DBSA)(0.5) (polyaniline doped only by HDBSA, the T(g)s (glass transition temperatures) of the polyblends decreased with PANI(DBSA)(0.5), indicating the presence of the compatibility that can alter the doping condition of PANI(DBSA)0.5 by changing the conjugation length. In the polyblend system, it was also confirmed when the polyblend of 50/50 showed a higher residue weight than the rest of polyblends after being heated up to 450 degrees C. The lambda(max), Of UV-ViS spectra of PANI (DBSA)(0.5) demonstrates a red shifts indicating the secondary doping effect (increasing conjugation length) was recovered when PANI(DBSA)(0.5) was mixed with less than 50% of AF(DBSA)(0.5) (HCI)(0.5). Similar phenomenon of red shift was found for the blended samples of PANI(DBSA)(0.5)/AF(DBSA)(1.0) at high temperatures. IR spectra revealed an alkyl affinity interaction is present between PANI(DBSA)(0.5) and AF(DBSA)(1.0) at room temperature and a strong and free localized polaron band appeared at high temperatures due to the recovery of secondary doping. (c) 2006 Wiley Periodicals, Inc. I Appl Polym Sci 103:2120-2128,2007