Segmental Dynamics and Dielectric Constant of Polysiloxane Polar Copolymers as Plasticizers for Polymer Electrolytes

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• 作者：U Hyeok Choi ; Siwei Liang ; Quan Chen ; James Runt ; Ralph H. Colby
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：February 10, 2016
• 年：2016
• 卷：8
• 期：5
• 页码：3215-3225
• 全文大小：730K
• ISSN：1944-8252

文摘

Dielectric relaxation spectroscopy was used to investigate the segmental dynamics of a series of siloxane-based polar copolymers combining pendant cyclic carbonates and short poly(ethylene oxide) (PEO) chains. The homopolymer with cyclic carbonate as the only side chain exhibits higher glass transition temperature T_g and dielectric constant ε_s than the one with only PEO side chains. For their copolymers the observed T_g (agreeing well with the predicted values from the Fox equation) and ε_s decrease with increasing PEO side chain content. These polar polymers exhibit a glassy β relaxation with Arrhenius character, attributed to local chain motions of side groups attached to the main chain, and a segmental α relaxation, associated with the glass transition with a Vogel temperature dependence. As PEO side chain content increases, narrowing of the local glassy β relaxation was observed in the copolymers. The segmental α dynamics were observed to be faster, with an increase in breadth and decrease in strength with increasing PEO side chain content. Owing to the trade-off between T_g and ε_s, copolymers of intermediate composition result in the highest ionic conductivity when these copolymers are used to plasticize Li single-ion conducting ionomers.