AbstractMicrotacticities of the polymers obtained by the radical polymerization of methacrylic acid (MAA) coordinated to amminecobalt(III) complexes, methacrylatopentaamminecobalt(III) perchlorate (1) and cis‐dimethacrylatotetraamminecobalt(III) perchlorate (2) were studied. It was found that macromolecules obtained by the copolymerization of 1 with MAA at pH 3 have much more isotactic sequences. However, microtacticities of the polymers obtained by the copolymerization of 1 at pH 7 or that of 2 at pH 3 were slightly influenced by the incorporation of metal complex monomers. From these results as well as from Pddl/Pdl and Δεp values, it was found that the penultimate effects play an important rôle in the determination of the steric placement. It has also to be considered that the electrostatic interactions between the reacting species also play a certain rôle in the determination of the microstructures since the tacticties are greatly influenced by the ionized state of the reacting species.