The results of the model reactions with ethanol or 2-propanethiol and acetic acid showed that the dehydration condensation of the ethanol reaction was chemoselective and that thioesterification did not occur under the conditions used. We synthesized polyesters with pendant mercapto groups by dehydration polycondensations of diols and TMA, and as with the model reactions, esterification proceeded chemoselectively and thioesterification did not occur. The pendant mercapto-containing polyesters had M(n)s > 1.0 x 10(4). We also demonstrated that the pendant mercapto groups could be chemically modified by glycosylation or cross-linked by TCDI to synthesize a gelatinous RAFT agent as a first example, which acted as a RAFT agent in a radical polymerization to afford poly(methyl methacrylate) with a narrow molecular weight distribution (M-n = 8.5 x 10(4), M-w/M-n = 1.47). These procedures could be used to produce new types of polyesters from monomers that differ in chirality and functionality and also nanoscale-reactive media containing RAFT agent as a cross-linker for controlled radical polymerization of vinyl monomers.