Yong-Kyung Lee

Synthesis and polymerization of Chiral methacrylates bearing a cholesteryl or menthyl group

Chiral methacrylates, that is, cholesteryl (ChMOC) and l-menthyl (MnMOC) N-(2-methacryloyloxyethyl)carbamates, were synthesized from 2-methacryloyloxyethyl isocyanate and cholesterol and l-menthol, respectively. Radical polymerizations of ChMOC and MnMOC gave number-average molecular weights for poly(ChMOC) and poly(MnMOC) of up to 3.74 × 104 and 9.39 × 104, respectively, and the specific rotations ([α]) were −43.1° to −47.7° and −87.6° to −89.0°, respectively. Temperature dependence of the specific optical rotation was observed for poly(ChMOC) but not for poly(MnMOC). The hydrogen bonds based on urethane segments for poly(ChMOC) were stronger than those for poly(MnMOC) according to IR spectra. In addition, the chiroptical properties of poly(ChMOC) were slightly affected by temperature in the presence of trifluoroacetic acid acting as an inhibitor for the formation of hydrogen bonds. Therefore, poly(ChMOC) may have a regular conformation due to hydrogen bonds and interaction between cholesteryl groups. Radical copolymerizations of ChMOC with styrene, methyl methacrylate, N-cyclohexylmaleimide, and N-phenylmaleimide were performed with 2,2′-azobisisobutyronitrile in tetrahydrofuran at 60 °C. Monomer reactivity ratios and Alfrey–Price Q–e were determined. Chiroptical properties of the copolymers were influenced by co-units. Thermal and X-ray diffraction analyses were performed for the homopolymers and copolymers.

Synthesis of novel chiral poly(methacrylate)s bearing urethane and cinchona alkaloid moieties in side chain and their chiral recognition abilities

Abstract Two types of new chiral methacrylates, cinchoninyl(2-methacryloyloxyethyl)carbamate (CIMOC) and cinchonidinyl(2-methacryloyloxy-ethyl)carbamate (CDMOC) were synthesized from 2-methacryloyloxyethyl isocyanate (MOI) and cinchona alkaloid such as cinchonine and cinchonidine, respectively. Radical polymerizations of CIMOC and CDMOC were performed under several conditions to obtain the corresponding polymers whose specific optical rotations ([ α ] 435 25 ) were 84.0–89.0° and 0.39–0.72°, respectively. From the results of radical copolymerizations of RMOC (CIMOC and CDMOC, M 1 ) with styrene (ST, M 2 ) or methyl methacrylate (MMA, M 2 ), monomer reactivity ratios ( r 1 , r 2 ) and Alfrey–Price Q – e were determined: r 1 =0.18, r 2 =0.48, Q 1 =0.53, e 1 =0.92 for the CIMOC–ST system; r 1 =0.53, r 2 =0.26, Q 1 =4.91, e 1 =1.80 for the CIMOC–MMA system r 1 =0.59, r 2 =0.47, Q 1 =0.86, e 1 =0.33 for the CDMOC–ST system; r 1 =0.28, r 2 =0.59, Q 1 =2.15, e 1 =1.74 for the CDMOC–MMA system. The chiroptical properties of the copolymers were strongly influenced by co -units. Poly(RMOC)-bonded-silica gel as chiral stationary phase (CSP) was prepared for high performance liquid chromatography (HPLC). The CSPs resolved some racemates such as mandelic acid and trans -2-dibenzyl-4,5-di( o -hydroxyphenyl)-1,3-dioxolane by HPLC. The chiral recognition ability of poly(RMOC) may be due to the interaction between some cinchona alkaloid units and the racemates and/or to secondary and higher-ordered structures of the polymer.

Synthesis and Characterization of Novel Vinyl Polymers Containing Thioester Group in Side Chain

There have been many reports on the synthesis of macromonomers using thiols such as 3-mercaptopropionic acid (3-MPA). Star-shaped polymers containing sulfur were prepared by the radical polymerizations of macromonomers, and properties for paints were studied. Mercapto-modified polymers were highly adsorptive against heavy metal ions and useful for chain transfer agents of the radical polymerization to synthesize graft copolymers. The substituted allylic sulfides obtained from thiols as chain transfer agents in the radical polymerization gave end-functional polymers of controlled molecular weight. From this point of view, thiols such as 3-MPA are very often utilized for polymerization retarders and regulators in the field of macromolecules. The objective of our studies was to search for effective and wide applications of thiols such as 3-MPA, except for the application for polymerization retarder and regulator. We previously reported on the synthesis and characterization of the polymers containing sulfur in the main chain using 3-MPA. It is difficult to synthesize vinyl compounds from thiols because addition reactions of thiols to olefins occur easily. Otsu et al. reported on the polymerization reactivities of alkyl thioacrylate. In this study we synthesized and polymerized the novel vinyl monomers methoxycarbonylethyl thioacrylate (MTA), methoxycarbonylethyl thiomethacrylate (MTM), and menthoxycarbonylethyl thiomethacrylate (MnTM), which had a thioester group in the side chain, from 3-MPA and methyl 3-mercaptopropionate (M3-MP). The monomers were homopolymerized and copolymerizationed with styrene (St), methyl methacrylate (MMA), or N-cyclohexyl maleimide (CHMI). The characterizations of the polymers are examined.