Abstract: The synthesis and characterization of novel multi-arm, polyisobutylene-based star-block polymers comprising a plurality of polyisobutylene-containing, diblock arms radiating from a siloxane core are described. The synthesis has been achieved by cationically polymerizing a monomer, such as styrene, and isobutylene to form diblock prearms and then hydrosilating the unsaturation-functionalized polyisobutylene with siloxanes carrying a plurality of Si—H groups via hydrosilation. The resultant star-block polymers may be thermoplastic elastomers characterized as having superior tensile strength and processing properties as compared to linear triblock polymers of similar hard/soft segments.