AbstractThe change of tacticity of methacrylate blocks in the anionic block copolymerization of ethylene oxide with methyl methacrylate ortert‐butyl methacrylate as function of the number of monomeric units in the poly(ethylene oxide) (PEO) sequences formed in the first polymerization step, was studied. The fraction of the syndiotactic triads of the polymethacrylates was found to increase with the DP of the PEO precursor. When the plateau value was reached, the tacticity was similar to that of poly(methyl methacrylate) initiated by alkali alkoxides when solvated with crown ethers. The variation of the tacticity was smaller withtert‐butyl methacrylate than with methyl methacrylate. The growth reaction of methacrylate monomers was found to follow Bernoullian statistics. It is assumed that the solvation of the counterions increases with increasing of the monomeric units in the starting poly(ethylene oxide) blo