ATROPISOMERISM IN POLYMERS. SCREW-SENSE SELECTIVE POLYMERIZATION OF ISOCYANIDES BY INHIBITING THE GROWTH OF ONE ENANTIOMER OF A RACEMIC PAIR OF HELICES.

Article abstract of DOI:10.1021/ja00213a034

The authors describe a method for the preparation of a polymer with an excess of either left- or right-handed helices, starting from an achiral isocyanide. To this end, they added a slowly polymerizing optically active isocyanide as comonomer to a rapidly polymerizing achiral isocyanide. CD spectra and optical rotation indicate that the screw sense of the resulting polymer samples is opposite to the one preferred by the homopolymer of the optically active comonomer. A mechanism is proposed according to which the optically active comonomer is preferentially incorporated in one of the two helices formed from the achiral isocyanide, viz. the one that corresponds to its own homopolymer.