Preferably, Q??? is ???SO2N(R1)R2???, ???(CH2)kO(CH2)kO(O)C???, ???(CH2)kO??? or ???CONR1???(CH2)kC(O)O??? where R1 is a hydrogen or lower alkyl group, such as a C1-C4 alkyl group; and R2 is an alkylene group or heteroalkylene group, preferably a C1-C4 alkylene group.