a linker group selected from the group consisting of ???COO???, ???OOC???, ???CH2???CH2???, a cis or trans double bond, or a triple bond, when d is 0 rings B and C are linked through a single bond; Y is an alkyl or fluorinated alkyl group having from one to six carbon atoms; and R1 is a nonchiral tail group selected from linear or branched alkyl groups where one or more non-neighboring CH2 groups