The effect of acid concentration on the aniline polymerization and on the structure and properties of polymers obtained have been investigated using FTIR

XPS and elemental analysis. The conductivity and structure of the polymers depend on the acid concentration of the polymerization solution. In medium concn. of 0.5-4 M

polymer having high conductivity and mainly 1

4-substituted benzen ring structure is obtained with high yield. In low concn. (0.001-0.4 M)

the contents of azo-group and 1

3-substituted benzen ring increase with decreasing acidity. When HCl conen. is higher than 5M

the conductivity and the content of quinoid-units decrease and 1

4-addition of HCl to the quinoid-units is observed.