Skip to Main content Skip to Navigation
Theses

Structure semi-cristalline et propriétés d'usage de films de copolymères fluorés électro-actifs : influence de la composition et de la mise en forme

Abstract : The relationship between semi-crystalline structure and properties of use (mechanical, dielectric and electroactive) of fluorinated copolymer films was studied for applications in organic electronics. Investigated materials are poly(VDF-co-TrFE) copolymers and poly(VDF-ter-TrFE-ter-CTFE) terpolymers based on vinylidene fluoride (TrFE), trifluoroethylene (TrFE) and chlorotrifluoroethylene (CTFE). Polymer films, obtained after solvent evaporation, are studied by X-ray diffraction (SAXS-WAXS), DSC, FTIR, DMA, dielectric spectroscopy and polarization cycles in order to highlight the impact of composition and processing (annealing, poling) on structure and final properties of material. We showed that the ferroelectric (FE) phase coexists with the defective ferroelectric (DFE) phase in copolymer films. The increasing fraction of DFE phase with TrFE content allows explaining the evolution of thermal properties. A continuous structural transition, from DFE phase to paraelectric (PE) phase was highlighted. The CTFE termonomer content highly influences the crystalline structure and the electro-actives properties of terpolymer films (loss of ferroelectric behavior in favor of relaxor ferroelectric (RFE) behavior).We proved for the first time the existence of a continuous structural transition between RFE phase and PE phase around room temperature. This transition allows explaining exacerbated properties of these materials (dielectric constant and deformation under electric field).Finally, analogies of behavior between copolymers and terpolymers are discussed, especially the evolution of crystalline phases under electric field, in order to better understand how these electro-active materials work for their future development at industrial level.
Complete list of metadatas

Cited literature [97 references]  Display  Hide  Download

https://pastel.archives-ouvertes.fr/tel-02957220
Contributor : Abes Star :  Contact
Submitted on : Monday, October 5, 2020 - 1:02:50 AM
Last modification on : Monday, October 5, 2020 - 3:28:19 AM

File

ESPCIFrancoisBargain2017.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-02957220, version 1

Collections

Citation

François Bargain. Structure semi-cristalline et propriétés d'usage de films de copolymères fluorés électro-actifs : influence de la composition et de la mise en forme. Chimie-Physique [physics.chem-ph]. Université Paris sciences et lettres, 2017. Français. ⟨NNT : 2017PSLET007⟩. ⟨tel-02957220⟩

Share

Metrics

Record views

139

Files downloads

14