Summary: Two sets of side‐chain, liquid‐crystalline ionomers based on copolymers of butyl acrylate and 4‐{[6‐(acryloyloxy)hexyl]oxy}benzoic acid containing 2.5–20 mol‐% of lithium or rubidium ions were studied. As the content of ions of alkali metals increases, segmental mobility markedly decreases. As compared with rubidium‐containing ionomers, ionomers containing lithium ions are characterized by a far more efficient decrease in their dielectric relaxation times because ionic radius of lithium ions is lower than that of rubidium ions.