Public Reporting Burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, Transport Properties of Sulfonated Poly(styrene-b-isobutylene-b-styrene) Triblock Copolymers at High Ion-Exchange Capacities Report Title ABSTRACTTransport properties of sulfonated poly(styrene-b-isobutylene-b-styrene) (S-SIBS) triblock copolymers were examined as a function of ion-exchange capacity (IEC), specifically at high IECs (up to ~2 mequiv/g). The proton conductivity of S-SIBS was ~1 order of magnitude higher than sulfonated polystyrene at similar IECs and 3-fold higher than Nafion 117 at an IEC of 2 mequiv/g. However, all polymers in this study possessed similar selectivities (i.e., proton conductivity/methanol permeability) regardless of chemistry or morphology. Smallangle X-ray scattering reveals a periodic-to-nonperiodic transition in S-SIBS with an anisotropic lamellar morphology oriented in the plane of the membrane at IECs ranging from 0.5 to 1 mequiv/g and an isotropic cocontinuous morphology at IECs ranging from 1.1 to 2 mequiv/g. This morphological transition coincides with a discontinuity in the IEC-dependent transport properties. In addition, S-SIBS transport properties were measured after solution casting from 15 different solvents at a constant IEC (0.8 mequiv/g). Transport properties varied by almost 3 orders of magnitude when comparing S-SIBS solution cast from toluene to a toluene/ethanol mixture. X-ray scattering results show morphological differences with solvent choice. This study demonstrates the significant impact of morphology on transport properties in ionic block copolymers. PennsylVania, Philadelphia, PennsylVania 19104 ReceiVed September 7, 2005; ReVised Manuscript ReceiVed October 20, 2005 ABSTRACT: Transport properties of sulfonated poly(styrene-b-isobutylene-b-styrene) (S-SIBS) triblock copolymers were examined as a function of ion-exchange capacity (IEC), specifically at high IECs (up to ∼2 mequiv/ g). The proton conductivity of S-SIBS was ∼1 order of magnitude higher than sulfonated polystyrene at similar IECs and 3-fold higher than Nafion 117 at an IEC of 2 mequiv/g. However, all polymers in this study possessed similar selectivities (i.e., proton conductivity/methanol permeability) regardless of chemistry or morphology. Smallangle X-ray scattering reveals a periodic-to-nonperiodic transition in S-SIBS with an anisotropic lamellar morphology oriented in the plane of the membrane at IECs ranging from 0.5 to 1 mequiv/g and an isotropic cocontinuous morphology at IECs ranging from 1.1 to 2 mequiv/g. This morphological transition coincides with a discontinuity in the IEC-dependent transport properties. In addition, S-SIBS transport properties...

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