Free-radical polymerization of (R)-(-)-1-(1-naphthyl)ethyl(2-methacryloyloxyethyl)urea and chiral recognition ability

(R)-(-)-1-(1-Naphthyl)ethyl(2-methacryloyloxyethyl)urea (NEMOU) was synthesized from 2-methacryloyloxyethyl isocyanate (MOD and (R)-(+)-1-(l-naphthyl)ethylamine. Radical homopolymerizations of NEMOU were performed in several solvents to obtain the corresponding chiral polymers that have hydrogen bonds based on urea moieties. Specific optical rotations of poly(NEMOU) changed by the measurement temperature, which may be attributed in part to change of conformation. From the results of radical copolymerizations of NEMOU with styrene (ST, M-2) or methyl methacrylate (MMA, MA monomer reactivity ratios (r(1), r(2)) and Alfrey-Price Q-e were determined: r(1) = 0.48, r(2) = 0.20, Q(1) = 1.41, e(1) = 0.74 for the NEMOU-ST system; r(1) = 0.55, r(2) = 0.16, Q(1) = 9.02, e(1) = 1.96 for the NEMOU-MMA system. The chiroptical. property of the copolymers was strongly influenced by comonomer units. To examine the chiral recognition ability of poly(NEMOU), chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were prepared from silica gel and poly(NEMOU). The CSPs resolved some racemates such as 1,2,3,4-tetrahydro-1-naphthol and N-benzyl-1-(1-methyl-2-methoxycarbonyl)ethylamine in n-hexane/2-propanol as mobile phase by HPLC. The chiral recognition ability of poly(NEMOU) may be ascribed not only to the interaction between the low molecular weight chiral selector and the racemates but also to the secondary and/or higher-ordered structure of the polymer.