The synthesis together with mechanical property and rheological characterization of novel star-block copolymers comprising multiple polystyrene (PSt)-b-polyisobutylene (PIB) arms emanating from polydivinylbenzene (PDVE) cores are described. The synthesis strategy involved the preparation of PSt-b-PIB-Cl-t (i.e., diblocks fitted with a tert-chlorine terminus at the PIB end) by sequential living block polymerization of St and IB, ionizing the -Cl-t terminus by TiCl4, at room temperature, and linking the PSt-b-PIBcircle plus prearms by DVB. Molecular characterization was effected mainly by triple detector GPC including refractive index (RI)-, UV-, and laser light scattering (LLS)-GPC traces. Evidence for intra- and intermolecular reactions between individual star-blocks is presented and a comprehensive mechanism to the final product is proposed. The stress-strain behavior of star-blocks has been studied and is compared with those of linear triblocks (i.e., two-arm stars) of similar arm molecular weights and composition in the 25-70 degrees C range. The mechanical properties of star-blocks are invariably superior to those of the triblocks over the entire temperature range. The rheological behavior of star-blocks and linear triblocks has been compared in terms of dynamic viscosity at various frequencies. Star-blocks exhibit significantly lower melt viscosities than their linear counterparts, which signals improved processing behavior. We have also compared select rheological properties of the commercially available PSt-b-(hydrogenated-1,4-polybutadiene)-b-PSt thermoplastic elastomer (Kraton G 1650) with those of PIB-based linear triblocks and multiarm star-blocks of similar glassy/rubbery compositions. The melt viscosities of PIB-based triblocks and star-blocks were significantly lower than that of Kraton G over the entire frequency range investigated.