Synthesis of Nano-Latex Particles of Optically Active Helical Substituted Polyacetylenes via Catalytic Microemulsion Polymerization in Aqueous Systems

This article reports oil the first catalytic microemulsion polymerizations Of substituted acetylenes in aqueous medium, providing nanoscale particles exhibiting optical activities and consisting of helical polymers. Three types of substituted acetylenes-one achiral N-propargylamide, two chiral N-propargylsulfamides, and chiral N-propaygylurea-were polymerized in the presence of hydrophobic Rh-based catalyst and with SDS as emulsifier and DMF as coemulsifier. Such microemulsion polymerizations led to nanoscale particles (70-110 nm in diameter) of polymers adopting helical conformations. The particles derived from the chiral monomers showed large specific rotations and intense circular dichroism (CD) signals. The obtained polymer dispersions demonstrated high stability. The thus-prepared polymers after removing the emulsifier and coemulsifier showed much stronger CD signals, and the helices were found to have higher thermal stability when compared with the corresponding polymers synthesized via catalytic polymerizations in organic solvents. The microemulsion polymerizations enable the polymers to form predominantly one-handed helical structures. The possible mechanisms were proposed for the formation of optically active polymer particles, for the formation of predominantly one-handed helices, and for the increased thermal stability of the helices formed in the polymers.