The First Suspension Polymerization for Preparing Optically Active Microparticles Purely Constructed from Chirally Helical Substituted Polyacetylenes

Suspension polymerization has been extensively utilized with vinyl monomers to prepare vinyl-polymer microparticles (mu m size; denoted MPs) with a variety of morphologies and significant applications. However, suspension polymerization of acetylenic monomers has remained a big challenge. This communication reports the first methodology for performing suspension polymerizations of acetylenic monomers, from which optically active microparticles (OAMPs) are constructed exclusively from helical substituted polyacetylenes. Chiral monomer (M1) and achiral monomer (M2) separately underwent suspension polymerization at room temperature in aqueous media in the presence of Rh-based catalyst with poly(vinyl alcohol) as a stabilizer, providing MPs (200-700 mu m) in high yield (>80%). The obtained OAMPs, both crosslinked and non-crosslinked, were characterized by SEM, polarimetry, circular dichroism, and UV-vis spectroscopy. The chiral substituted polyacetylene chains constituting the MPs were found to adopt helices of predominantly one-handed screw sense, affording the particles with pronounced optical activity. The MPs derived from achiral M2 exhibited optical inactivity. The present study opens up new opportunities for preparing novel (non-) crosslinked microparticles derived from acetylenic monomers.