PURPOSE: To obtain a methyl methacrylate polymer complex at low cost by the ionic polymerization of a methyl methacrylate monomer by using a Grignard reagent, followed by the suspension polymerization in water of the polymer so obtained.

CONSTITUTION: Methyl methacrylate(MMA) is ionically polymerized in the presence or absence of a solvent using a Grignard reagent as an initiator. The resultant liquid polymer is suspension-polymerized in water to produce a complex of an isotactic (abbreviated to Iso- hereunder) MMA polymer and a syndiotactic (abbreviated to Syn- hereunder) MMA polymer. tert-Butylmagnesium bromide is preferably used as the Grignard reagent, giving a highly isotactic MMA polymer. The ionic polymerization is effected in an inert gas atmosphere preferably in the presence of a solvent such as toluene that suppresses side reactions. In the suspension polymerization, a dispersant such as polyvinyl alcohol and a known radical polymerization initiator are used, and the polymerization conditions are controlled so that a given amount (based on the Iso-MMA polymer) of MMA is polymerized to obtain a 1:9-9:1 polymer composition comprising the Iso- and Syn-MMA polymers.