Multiblock Copolymers of Styrene and Butyl Acrylate via Polytrithiocarbonate-Mediated RAFT Polymerization

When linear polytrithiocarbonates as Reversible Addition-Fragmentation chain Transfer (RAFT) agents are employed in a radical polymerization, the resulting macromolecules consist of several homogeneous polymer blocks, interconnected by the functional groups of the respective RAFT agent. Via a second polymerization with another monomer, multiblock copolymers—polymers with alternating segments of both monomers—can be prepared. This strategy was examined mechanistically in detail based on subsequent RAFT polymerizations of styrene and butyl acrylate. Size-exclusion chromatography (SEC) of these polymers showed that the examined method yields low-disperse products. In some cases, resolved peaks for molecules with different numbers of blocks (polymer chains separated by the trithiocarbonate groups) could be observed. Cleavage of the polymers at the trithiocarbonate groups and SEC analysis of the products showed that the blocks in the middle of the polymers are longer than those at the ends and that the number of blocks corresponds to the number of functional groups in the initial RAFT agent. Furthermore, the produced multiblock copolymers were analyzed via differential scanning calorimetry (DSC). This work underlines that the examined methodology is very well suited for the synthesis of well-defined multiblock copolymers.