Synthesis Of Poly (N-Propargylamide) Nanoparticles And Their Optical Activity

Helical substituted poly(N-propargylamide) have gathered great interest due to the structural features and potential applications in particular chiral recognition/resolution and chiral catalysis. In the course of research, it is found that large parts of the poly(N-propargylamide) in particular with bulky pendent groups are poor in solubility. Some helical poly(N-propargylamide) loose the helical conformation under varied condition, especially at elevated temperatures. In addition, little progress has been made in their practical applications. To circumvent the limitations and to prompt the relevant application research, in this study, we prepared a series of nanoparticles consisting of poly(N-propargylamide) via three different ways, including self-assembly of amphiphilic copolymer, emulsification of pre-formed polymers and monomer emulsion polymerization.N-Propargylgluconicamide (monomer 1) was successfully synthesized with N-propargylamide and 8-gluconolactone, and was characterized. The corresponding water-soluble poly(N-propargylgluconicamide) (polymer 1) was polymerized with hydrophilic Rh catalyst ([Rh(C8H12)2]BF4) and were characterized with IR,1H NMR, GPC and CD. Moreover, an amphiphilic poly(N-propargylamide) (copolymer) synthesized by copolymerization of monomer 1 and N-(prop-2-yn-1-yl)hexanamide (monomer 2) was found to form molecular aggregates in water.A novel approach, i.e., emulsification, was developed to prepare nanoparticles from polymers prepared in advance. For optically active helical polymers, the resulting emulsions also show optical activity, and vice versa. The size of the nanoparticles is highly dependent on the emulsifier concentration. For the helical polymers with not-so-bulky pendent groups, considerable blue shifts occurred, while the bulky pendent groups did not cause blue shifts. The present study provides significant information for us to understand the unique category of nanoparticles consisting of helical poly(N-propargylamide) and showing optical activities.Nanoscale particles exhibiting optical activities and consisting of helical polymers were provided via monomer emulsion polymerizations of substituted acetylenes in aqueous medium. Chiral N-propaygylureas were polymerized in the presence of hydrophobic Rh-based catalyst and with triton X-100 as emulsifier and DMF as coemulsifier. Such microemulsion polymerizations led to nanoscale particles (70-300 nm in diameter) of polymers adopting helical conformations. The particles showed intense circular dichroism (CD) signals. However, the obtained polymer dispersions were found to demonstrate the CD signals opposite to the corresponding polymers in organic solvents, no matter the polymers were synthesized via catalytic polymerizations or monomer emulsion polymerization. The possible mechanisms were studied in the possible aspects, i.e., the emulsifier, the coemulsifier and also the way to provide the particles.