Macromolecular Dynamics of Sulfonated Poly(styrene-b-ethylene-ran-butylene-b-styrene) Block Copolymers by Broadband Dielectric Spectroscopy

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Polymers and High Performance Materials


Macromolecular dynamics of sulfonated poly(styrene-b-ethylene-ran-butylene-b-styrene) (sSEBS) triblock copolymers were investigated using broadband dielectric spectroscopy (BDS). Two main relaxations corresponding to the glass transitions in the EB and S block phases were identified and their temperature dependences were VFT-like. T-g for the S block phase shifted to higher temperature due to restrictions on chain mobility caused by hydrogen bonded SO3H groups. While the EB block phase T-g appeared to remain constant with degree of sulfonation in DMA experiments, it shifted somewhat upward in BDS spectra. A low temperature relaxation beneath the glass transition of the EB block phase was attributed to short range chain motions. The Kramers-Kronig integral transformation was used to calculate conductivity-free loss permittivity spectra from real permittivity spectra to enhance true relaxation peaks. A loss permittivity peak tentatively assigned to relaxation of internal S-EB interfacial polarization was seen at temperatures above the S block phase glass transition, and the temperature dependence of this relaxation was VFT-like. The fragilities of the EB and S block domains in sulfonated SEBS decreased after sulfonation. The temperature dependence of the dc conduction contribution to sSEBS loss spectra also followed VFT-like behavior and S block segmental relaxation time correlated well with conductivity according to the fractional Debye-Stokes-Einstein equation. (C) 2011 Elsevier Ltd. All rights reserved.

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European Polymer Journal





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