Optical activity as a tool in the investigation of the conformational equilibria of poly‐α‐olefins in solution

Abstract

AbstractAn attempt has been made to evaluate the contribution derived from the investigation of optically active poly‐α‐olefins to our knowledge of the conformational equilibria of isotactic vinyl polymers in solution. The data obtained from the measurement of optical rotation and its temperature coefficent, as well as of optical rotatory dispersion, in solution, leaves little doubt about the existence, for the most stereoregular poly‐α‐olefin, in solution, of main chain sections spiralized in both screw senses with one of the two screw senses prevailing. For a given degree of stereoregularity the length and the prevalence of the chain sections spiralized in the more favored screw sense depend on the structure of the lateral chains; the type of screw sense prevailing depends on the absolute configuration of the asymmetric carbon atoms contained in the monomers. This qualitative model has been confirmed by a series of experiments, including measurements of chiroptical properties in the solid state and determination of the end‐to‐end distance and copolymerization of chiral with nonchiral monomers. The possibility of extending the above model to include polymers containing functional groups for which no suitable method exists to relate optical activity to conformation and the consequences of ordered conformations for the isotactic vinyl polymers in solution are briefly discussed.