The Synthesis And Application Of Chiral Bisacylphosphine Oxides In Helix-Sense-Selective Photopolymerization

Helical polymers not only have unique structures and properties but also possess significant potential applications, including asymmetric synthesis, separation of enantiomers; asymmetric catalysis and the field of optical materials. As one of the synthetic methods of helical polymers, free radical polymerization has the advantage of simple operation, low purity of monomer and solvent and being suitable for wide range of monomers. In the radical polymerization of bulky vinyl monomers, helix-sense selection is governed by the chirality of a monomer itself or an additive. Therefore, as one of determining factors of helix-sense-selective polymerization, the synthesis and the helical induction ability of chiral additives would be an important research task. In this dissertation, the research progresses at home and abroad on helical polymers were reviwed, including the synthesis, classification methods and structural characterization of helical polymers and factors which influence the formation of the helical polymers.The main contents are listed below:1) Design and synthesis of optically inactive vinyl monomers with bulky groups. These vinyl monomers including:triphenylmethyl methacrylate,1-phenyldibenzo-suberyl methacrylate,9-phenylfluoren-9-yl methacrylate,9-ethylfluoren-9-yl methacrylate,9-cyclohexylfluoren-9-yl methacrylate, naphthalen-1-yl methacrylate, N-methyl-N-phenylmethacrylamide, N-(2,4,6-trichlorophenyl) methacrylamide,4,4-dimethyl-1-penten-3-one,4,4,4-triphenyl-1-buten-3-one and4,4,4-triphenyl-1-butene.2) Three new chiral bisacylphosphine oxide photoinitiators were prepared by the reaction of dilithium phosphides with acid chlorides to obtain acylphosphines and subsequent oxidation the resulting acylphosphines to give acylphosphine oxides. These bisacylphosphine oxides are:(-)-bis(menthylformyl)phenylphosphine oxide (BMPPO),(+)-bis(2,4,6-trimethylbenzoyl)menthylphosphine oxide (BTMPO) and (-)-bis(menthylformyl)menthylphosphine oxide (BMMPO).3) The synthesized chiral bisacylphosphine oxides were used as photoinitiators for radical polymerization of1-phenyldibenzosuberyl methacrylate (PDBSMA) under UV. The research results indicated that the polymerization initiated by these photoinitiators is helix-sense-selective. Highly isotactic, optically active polymers were obtained. Based on the chiroptical properties of the obtained poly(PDBSMA), such as optical activity and circular dichroism (CD) spectra, confirmed that the polymer has a single-handed helical conformation. The chemical structures of photoinitiators and the feed molar ratio of monomer to photoinitiator and the polymerization temperature have an influence on the helix-sense-selectivity. Among the three prepared chiral bisacylphosphine oxides, the helix induction ability of (-)-bis(menthylformyl)- menthylphosphine oxide is highest, the highest specific rotation of poly(PDBSMA) at365nm is+416°. The lower feed ratio of the monomer to photoinitiator and higher polymerization temperature are favorable to the increase of the helix-sense-selectivity. In addition, the chiral induction ability of these bisacylphosphine oxides toward other bulky vinyl monomers had been tested, but the helix-sense-selectivity is less.