Stereospecific polymerization of asymmetric α‐olefins having different optical purity

The polymerization of racemic and optically active α‐olefins having optical purity from 10 to 95% has been investigated by several ZIEGLER‐NATTA catalysts. Especially in the case of 3.7‐dimethyl‐1‐octene (I) the polymerization appears to be stereoselective, the predominant antipode being polymerized with higher specific rate. The stereoregularity of polymers from I and from 4‐methyl‐1‐hexene (II) slightly increases with monomer optical purity as shown by solvents extraction, IR spectra, and optical rotation; however a remarkable role is played by the catalytic system. The distribution of R and S units in polymer fractions having different stereoregularity has been also investigated by polymerizing a mixture of (R)‐II and (S)‐II‐1‐14C and possible relationships between stereoregulation and stereoselectivity are discussed. No particular effect of monomer asymmetric structure on polymerization stereochemistry has been observed in the case of 5‐methyl‐1‐heptene (III).