| Abstract: | We report the polymerization of phenyl isocyanides with the chiral palladium(II) initiating system. The resulting polymers with optically active properties were obtained by polymerization of the racemic isocyanide monomer(rac-1), and enantiomerically unbalanced polymerization of the monomer was found, providing substantial evidence for the enantiomer-selective polymerization of rac-1 mediated through chiral catalyst. A comparison between the enantiomerically pure monomers, 4-isocyanobenzoyl-L-alanine decyl ester(1 s) and 4-isocyanobenzoyl-D-alanine decyl ester(1 r), revealed a drastic discrepancy in the reactivity ratio of their homopolymerizations.It turned out that the monomer reactivity ratio of 1 s was higher than that of 1 r with chiral ligands. The results clearly demonstrated the inclination for incorporation of the 1 s enantiomer during the polymerization process and thus resulted in the enantiomer-selective polymerization in this system. The effects of the catalyst chirality on the optically active properties of polymerization were investigated,and it was concluded that the formation of higher-ordered conformation with a handed helicity might be attributed to the chiral induction of chiral palladium(II) catalyst. Moreover, the polymers obtained through the enantiomer-selective polymerization of the enantiomerically pure monomer were with a significant improvement of the optical activity if the chirality of the monomer and the catalyst matched with each other. |
