| abstract |
wherein R1 is a linear or branched alkyl group having a carbon atom number of 2 to 20, a cyclic alkyl group having a carbon atom number of 3 to 20, or a linear or branched alkenyl group having a carbon atom number of 12 to 20; and Ar is a C6-18 aryl group unsubstituted or optionally substituted with at least one substituent selected from the group consisting of a C1-10 alkyl group, a C1-10 alkoxy group, a C6-18 aryloxy group, a halogen atom, a nitro group, a phenyl group, a C2-10 alkylcarbonyl group, and a C7-18 aralkyl group. |