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Stereospecific Polymerizations of Methacrylic Esters Having Hetero Atoms in Their Pendant Alkyl Groups

Various methacrylic esters with and without hetero atoms in their pendant ester groups were polymerized in toluene or in THF at −78°C using n-BuLi LiAlH4, or i-BuMgBr as an initiator. By comparing the isotacticities of the resultant polymers using the NMR spectral method, the influence of the hetero atom in the pendant ester group of the monomer on polymer stereoregularity was clarified. The experiments showed that the isotacticities of those polymers containing nitrogen or oxygen atoms in their side chains were lower than the isotacticites of those not containing such atoms. On the basis of these results the assumption was made that such depressing effects in isotactic propagation were caused by Lewis basicity of the nitrogen or oxygen atoms in the pendant ester groups. Furthermore, the effect of THF added to the polymerization reaction mixture, the effects of monomer concentration, the number of carbon atoms between the hetero atom and ester oxygen, and of the counter cation, all substantiated this assumption. The effect of hetero atoms on the syndiotacticities of the resultant polymers was also briefly studied.