NOVEL POLYISOBUTYLENE POLY(DIMETHYLSILOXANE) BICOMPONENT NETWORKS - I- SYNTHESIS AND CHARACTERIZATION/

The synthesis of novel polyisobutylene (PIB)/poly( dimethylsiloxane) ( PDMS) bicomponent networks is described. The synthesis strategy( see F igure 1) was to prepare well-defined and -characterized allyl-tritelec helic 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 isobutyle ne polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi-PDMS-SiH was obtained by equilibrium polymerization o f 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 varyin g compositions and average molecular weights between crosslinks ((M) o ver bar(c)) of similar to 20,000 g/mol were assembled. Optimum crossli nking conditions were defined in terms of H2PtCl6 catalyst concentrati on, nature of solvent, time, temperature, and stoichiometry of similar to CH2CH=CH2/similar to SiH groups, allowing for the convenient synth esis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy. (C) 1998 John Wiley & Sons, Inc.