The synthesis of novel polyisobutylene (PIB)/poly( dimethylsiloxane) (PDMS) bicomponent networks is described. The synthesis strategy( see Figure 1) was to prepare well-defined and -characterized allyl-tritelechelic polyisobutylenes [phi(PIB-C-C=C)(3)] and SiH-ditelechelic poly( dimethylsiloxanes) (HSi-PDMS-SiH) and then crosslink these moieties by hydrosilation. The phi(PIB-C-C=C)(3) was prepared by Living isobutylene polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi-PDMS-SiH was obtained by equilibrium polymerization of octamethylcyclotetrasiloxane and tetramethyldisiloxane. The detailed structures of the starting polymers were characterized by GPC and H-1-NMR spectroscopy. A series of PIB/PDMS bicomponent networks of varying compositions and average molecular weights between crosslinks ((M) over bar(c)) of similar to 20,000 g/mol were assembled. Optimum crosslinking conditions were defined in terms of H2PtCl6 catalyst concentration, nature of solvent, time, temperature, and stoichiometry of similar to CH2CH=CH2/similar to SiH groups, allowing for the convenient synthesis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy.