Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers

Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers

Bibliographic Details
Main Author: Yang, Lianyun
Language:English
Published: Case Western Reserve University School of Graduate Studies / OhioLINK 2015
Subjects:
Polymers
polymer
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=case1431686125
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-case14316861252021-08-03T06:31:26Z Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers Yang, Lianyun Polymers polymer High dielectric constant and low loss polymer dielectrics are desired for applications such as energy storage, electrocaloric cooling, and electrostrictive actuation. Several types of polarizations can be utilized to enhance dielectric constant of polymer dielectrics. Polymers with permanent dipoles can be good candidates to achieve high dielectric constant and low loss properties because of their dipolar polarization. There are several situations of dipolar polarization for polar polymers with permanent dipoles, which depend on different dipole/domain structures. Our work focuses on the novel ferroelectric behavior of ferroelectric polymers. The mechanism for novel ferroelectric behavior can be explained by the crystal pinning effect from crystal isomorphism. The physical pinning effect in P(VDF-TrFE-CFE) is weak and double hysteresis loop (DHL) is thus observed. The chemical pinning effect in e-beam P(VDF-TrFE) or P(VDF-TrFE-CTFE) is strong and only single hysteresis loop (SHL) is observed.Besides P(VDF-TrFE-CTFE), DHLs can also be achieved in P(VDF-TrFE-TrFE)-g-PS graft copolymer by the nanoconfined effect. Crystal orientation and temperature effects on the DHL behavior of the graft copolymer were studied. Clear dielectric, rather than ferroelectric, behavior is observed from the non-oriented graft polymer sample. But stable DHLs are observed for the oriented films up to 75 C. Above 100 C, huge broadening of the D-E loops shows up due to the electrical conduction and ion migrational losses.The electrical conduction loss plays an important role on the insulation property of dielectric polymers, especially at high temperatures and under high electric fields. As an example, a commercial biaxially oriented PVDF (BOPVDF) film was selected to study the electrical conduction under different electric poling conditions. The dipoles from either amorphous or crystalline phase do not have much influence on the electronic conduction. The electronic conductivity for the BOPVDF film is low below 25 C. Above 25 C, the electronic conductivity first increases, then decreases upon increasing the poling fields. These changes can be attributed to the effect from polarized ions. Above 75 C, electronic conductivity substantially increase due to injected space charges. Meanwhile, PVDF starts to undergo electrochemical reactions, emitting HF gas which can corrode metal electrodes. 2015-09-04 English text Case Western Reserve University School of Graduate Studies / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=case1431686125 http://rave.ohiolink.edu/etdc/view?acc_num=case1431686125 unrestricted This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center.
collection NDLTD
language English
sources NDLTD
topic Polymers
polymer
spellingShingle Polymers
polymer
Yang, Lianyun
Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
author Yang, Lianyun
author_facet Yang, Lianyun
author_sort Yang, Lianyun
title Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
title_short Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
title_full Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
title_fullStr Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
title_full_unstemmed Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers
title_sort novel ferroelectric behavior in poly(vinylidene fluoride-co-trifluoroethylene)-based random copolymers
publisher Case Western Reserve University School of Graduate Studies / OhioLINK
publishDate 2015
url http://rave.ohiolink.edu/etdc/view?acc_num=case1431686125
work_keys_str_mv AT yanglianyun novelferroelectricbehaviorinpolyvinylidenefluoridecotrifluoroethylenebasedrandomcopolymers
_version_ 1719438302546755584

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