Emulsion copolymerization of substituted acetylenes for constructing optically active helical polymer nanoparticles. Synergistic effects and helicity inversion

Abstract

Copolymerizations of substituted acetylenes have been intensively studied in solution polymerization for constructing chirally helical polymers, while emulsion copolymerizations of the kind of monomers have been only scarcely reported. In the present study, chiral substituted acetylene monomer containing cholic acid group underwent emulsion copolymerizations with an achiral acetylenic monomer in the presence of rhodium catalyst, providing optically active helical copolymer nanoparticles. Synergistic effects were found in the resulting helical copolymers, enabling one certain copolymer to show the maximum CD signal intensity. Moreover, the helicity of the helical copolymers in nanoparticle state was opposite to that in solution state. This is the first demonstration that synergistic effects and helicity inversion simultaneously occurred in helical copolymers prepared by emulsion copolymerization process. To deepen the understanding of the unique phenomena, corresponding solution copolymerization and emulsification process were also investigated. Different from "Sergeant and Soldiers rule" approach, the present study provides a new strategy for preparing chirally helical polymer particles by making full use of achiral monomers.