Single ion conductors, based on polymerized ionic liquids (PILs) with a polythiophene backbone bearing imidazolium salts with butyl, hexyl, octyl, and decyl side groups and six different counteranions ([Br](-), [BF4](-), [ClO4](-), [PF6](-), picrate, and [B(Ph)(4)](-)), are synthesized and studied with respect to the thermal, structural, and ion-conductivity properties. PILs bearing the polythiophene backbone are unique as they can simultaneously conduct electronic charge and ions at nanometer length scales. In addition, the pi-pi stacking of the polythiophene backbones results in exceptional smectic-like order. Increasing side group length from butyl to decyl increases the room temperature conductivity by 4 orders of magnitude (internal plasticization). Anion size (anionic radii from 0.19 to 0.44 nm) affects both the structure (from smectic-like to amorphous with increasing anion radius) and the ionic conductivity. Conductivity values differ by 6 orders of magnitude by varying anion size at ambient temperature. As a result, conductivities as high as 2 x 10(-3) S/cm could be obtained at high temperatures. Differences in conductivity are discussed in terms of changes in glass temperature (T-g), anion size, and value of dielectric permittivity. Overall ion transport in PILs based on polythiophene backbones is controlled by the low T-g, value of dielectric permittivity, smectic layering, and ion association lengths not exceeding a single smectic layer.