“Sergeants and soldiers rule” in helical substituted polyacetylene-derived copolymer nanoparticles

This article reports on the catalytic emulsion copolymerizations of chiral/achiral substituted acetylene monomers. An achiral N-propargylamide monomer underwent copolymerizations separately with two enantiopure monomers of chiral N-propargylsulfamide in the presence of (nbd)Rh+B−(C6H5)4 as catalyst and with Triton X-100 as emulsifier. The obtained (co)polymer emulsions demonstrated high stability and optical activity. Transmission electron microscopy (TEM) and gel permeation chromatography (GPC) techniques in combination demonstrated the successful formation of nanoparticles (100‒300 nm in diameter) constructed by copolymers. Circular dichroism and UV-vis absorption spectra showed that the (co)polymer chains in the nanoparticles adopted helical structures of a predominant helicity, which enabled the copolymer nanoparticles to show optical activity. Compared to the corresponding nanoparticles of the homopolymers, the nanoparticles constructed by the copolymers exhibited blue shifts in circular dichroism (CD) and UV-vis spectra. The present study demonstrated that the copolymers prepared via emulsion polymerization approach followed the “sergeants and soldiers rule.”