Poly(vinylphosphonic acid)-imidazole (PVPA-xIm) exhibits high proton conductivity above 100 degrees C. The high proton conductivity of PVPA-2Im depends on the molecular motions of Im. Molecular dynamics simulations conducted herein showed that the intercalation of Tm and imidazolium into PVPA reduces the translational motion of Tm in PVPA-2Im. The activation energy of the internal motion of Tm is lower than that of the translational motion, indicating that proton conduction in PVPA-2Im occurs via a Grotthuss-type mechanism.