About dielectric relaxation in highly cross-linked poly(ethylene oxide)

• Published in: Ionics
• Main Author: 2-s2.0-85058373034
• Format: Article
• Language: English
• Published: Institute for Ionics 2019
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058373034&doi=10.1007%2fs11581-018-2795-9&partnerID=40&md5=709b18317f714405653a623a9f1ee505

The effect of lithium salt on dynamics in highly cross-linked poly(ethylene oxide) (PEO) has been investigated. The elaboration uses results of dielectric relaxation studies. It turns out that competition of electric and structural relaxation coins conductivity mechanism. Neat cross-linked PEO with low mesh size can be transferred in super-cooled liquid state. Then, cross-linked PEO behaves like a hydrogen-bonded liquid since crystallization is strongly suppressed. As a result, one observes slow Debye-like relaxation at low temperature. It disappears after addition of salt since interaction of salt with polymer chains is stronger than the hydrogen-bonded network in the neat polymer. Analysis of tangent-loss spectra shows: Particle density governing dc conductivity does not depend on temperature at low concentration of added salt. It increases with temperature for neat cross-linked PEO and PEO loaded with sufficiently high concentration of salt. Prevention of crystallization requires a tight network of cross-links. Scaled representations of relevant impedance data for neat cross-linked PEO over extended ranges of frequency and temperature reveal that electric and structural relaxations are independent of temperature to good approximation at low and high frequency. There is a range of damped network oscillations, sandwiched between these limits, where relaxation becomes dependent on temperature. This range lessens with temperature. It does not occur at all in salt-comprising cross-linked PEO. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.