It is demonstrated that the oxidative doping of polyacetylene can be applied not only to the preparation of highly conducting materials but also to molecular dispersion of anionic species with interesting catalytic properties such as for example 12-molybdophosphoric anions which exhibit enhanced catalytic activity when inserted to polyacetylene. The detailed spectroscopic studies show that the structural identity of the Keggin unit is preserved upon incorporation to the polymer matrix and none of 12 molybdenum atoms is reduced in this process. Although the dopant is uniformly distributed on the surface of individual fiber, its distribution in the bulk of the fiber is not homogeneous and its inner parts remain intact.