The stereospecific polymerization of alkyl acrylates by organometallic compounds

Stereoregular polymerizations of n ‐butyl, isobutyl, sec ‐butyl, tert ‐butyl and methyl acrylates were studied with a radical initiator, as well as homogeneous and heterogeneous anionic catalysts. Polyisobutyl, ‐ sec ‐butyl and ‐ tert ‐butyl acrylates were obtained in a crystalline form by use of a heterogeneous organometallic compound, such as strontium‐zink tetraethyl as catalyst at low temperature. Poly‐ n ‐butyl acrylate prepared by strontium‐zinc tetraethyl complex was shown to be amorphous, but markedly different in its infrared spectrum from the authentic amorphous, poly‐ n ‐butyl acrylate, prepared with azo‐bis‐isobutyronitrile (AIBN). polyacrylic acid obtained from the strontium‐zinc tetraethyl catalyzed poly‐ n ‐butyl acrylate gave a crystalline X‐ray photograph. Amorphous polymethyl acrylate prepared by the above heterogeneous anionic catalyst was hydrolyzed to give rise to a crystalline polyacrylic acid. It can generally be said that heterogenous organometallic compound systems were often favorable for the stereoregular polymerizations of acrylates.