A trithiocarbonate RAFT agent was modified with a pyridyl disulfide group and used in the direct synthesis of endgroup pyridyl disulfide-functionalized homo- and amphiphilic 'block copolymers of oligo (ethylene glycol) acrylate (PEG-A) and butyl acrylate (BA). Both the homoand copolymerizations were found to be well controlled via the RAFT mechanism. The NMR analysis indicated that both the homopolymers of PEG-A and the amphiphilic diblock copolymers of PEG-A and BA possessed pyridyl disulfide terminal groups. A UV-Vis absorption test revealed that the pyridyl disulficle endgroup of the polymer could be efficiently used to couple thiol-bearing molecules to the polymer without the need for any post-polymerization modification. This communication presents the first efficient direct synthesis of thiol-reactive endgroup-functionalized well-defined polymers via the RAFT technique.