Effect of aniline formaldehyde resin on the conjugation length and structure of doped polyaniline: Spectral studies

A DBSA (n-dodecylbenzene sulfate)-complexed aniline formaldehyde [AF(DBSA)(1.0)] was successfully synthesized with excess aniline (compared with formaldehyde) in the presence of n-dodecylbenzene sulfonic acid (HDBSA), which was complexed with aniline monomer before polymerization. The resin was carefully characterized with H-1 and C-13 NMR, electron spectroscopy for chemical analysis, and Fourier transform infrared and was demonstrated to be a polymer in which anilines were all complexed with HDBSA and became anilinium salts. A drastic decrease of the maximum absorption wavelength (ultraviolet-visible spectra) of DBSA-doped polyaniline [PANI(DBSA)(0.5)] was found when AF(DBSA)(1.0) was mixed, and this resulted from the reduced conjugation length. A similar effect on PANI(DBSA)(0.5) was found when free HDBSAs were mixed with PANI(DBSA)(0.5). Visual inspection with an optical microscope revealed that PANI(DBSA)(0.5)/AF(DBSA)(1.0) gave uniform morphologies in various compositions, showing possible miscibility for this system. X-ray diffraction patterns of PANI(DBSA)(0.5)/AF(DBSA)(1.0) showed that the layered structure of PANI(DBSA)0.5 was still present but became shorter in the polyblend because of the presence of AF(DBSA)1.0. Solid-state C-13 NMR spectra revealed that the reduced conjugation length was derived from the interaction of alkyl groups between HDBSA, complexed. DBSA, and dopant DBSAs. (c) 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3116-3125, 2005.