Helix-Sense-Selective-Polymerization And "Majority Rules" In Emulsion Polymerization Of Substituted Acetylenes

Helical polymers can be obtained by emulsion polymerization of substituted acetylene monomers. These helical polymers with unique secondary structures show optical activity under certain conditions. The optically active helical polymers can be synthesized from chiral monomers or achiral monomers by asymmetric polymerization. Usually, the optical activity of helical polymers can show amplified chirality, compared with the corresponding small organic molecules. Here we firstly introduced the major kinds of asymmetric polymerizations and the related mechanism.The major contents in this thesis are as follows:The helical-sense-selective-emulsion-polymerization was achieved. The optically active nanoparticles were synthesized from achiral substituted acetylene monomers under the complex of [(nbd)RhCl]2 and chiral PEA in emulsion polymerization. The morphology of the nanoparticles was observed by TEM, and the optical activity of the nanoparticles was measured by CD and UV-vis absorption spectra. By the sol-gel reaction of TEOS, the core/shell nanoparticles were obtained. The thermal stability of the core was improved by forming the SiO2 shell.The "sergeants and soldiers effect" and "majority rules" are the two aspects of the "amplification of charity". Here we successfully prepared a series of helical (co)polymeric nanoparticles via catalytic emulsion polymerization approach. From the results of CD and UV-vis absorption spectra, we can conclude that the optical activity of the copolymeric nanoparticles consisting of enantiomeric acetylenic monomers followed the "majority rules". In the CD spectra, we find an interesting result that the maximum CD wavelength of the homopolymers and the copolymers were not the same. Namely, "blue shift" occurred to the copolymers. We think this phenomenon may be caused by the co-existence of a pair of enantiomeric monomer units and/or both right-and left-handed helices in the copolymer chains; at the junctions between the two types of monomer units and between the two types of helices with opposite screw sense, repulsion may be resulted from stereo effect. This force repulsion further made the length of conjugated copolymer chains shortened, so blue shift took place in the copolymers.