Synthesis of Arborescent Polystyrenes via an Inimer-Type Reversible Addition- Fragmentation Chain Transfer (RAFT) Polymerization"

High molecular weight polymers of randomly branched (dendritic or arborescent) architecture have unique physical and rheological properties. We believe that the unique properties of natural rubber may be due to such architecture. Dendritic rubbers have proven to be difficult to synthesize in an industrially viable manner. The Puskas group successfully synthesized high molecular weight polyisobutylenes using the polymerization concept called the inimer (initiator-monomer) method. Our goal is to extend this concept to a controlled free radical polymerization process called Reversible Addition-Fragmentation Chain Transfer (RAFT) to develop a one-pot method of synthesizing dendritic polyisoprene, SBR and other rubbers. This work describes the RAFT copolymerization of styrene. The number-average molecular weight (Mn) of the polymers was much higher than theoretically calculated for a linear polymerization, which suggests that a high degree of branching is occur. The average number of branches per molecule (B) was calculated. The polymerization retained the controlled behavior associated with typical RAFT polymerizations. This study shows the potential or this type of polymerization in synthesizing rubbers of arborescent architecture.