Poly(2,3-dimethylaniline) (P(2,3-DMA)) was synthesized chemically by using phosphoric acid (H3PO4) as protonic acid. The optimum ratio for n(H3PO4)/n(2,3-DMA)/n(APS) was 2.5/1/2, and the optimum temperature was 30 degrees C. The spectra of ultraviolet-visible and infrared demonstrate that the structure of P(2,3-DMA) was similar with polyaniline (PANI) except for the 2,3-ortho-substitute methyl. The result of X-ray diffraction and solubility analysis indicate that owing to the 2,3-ortho-substitute benzene ring, the P(2,3-DMA) has poorly partial crystallinity and better solubility. In addition, the anticorrosion property of P(2,3-DMA) was better than PANI. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013