structural evolutions in electroactive poly(vdf-co-trfe...

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Structural evolutions in electroactive poly(VDF-co-TrFE) copolymers for organic electronics

François Bargain, Sylvie Tencé-Girault, Fabrice Domingues Dos Santos, Michel Cloitre

Soft Matter and Chemistry Laboratory

10/03/16 – New-Orleans-USA

PVDF-based semi-crystalline polymers 2/16

Fluoropolymer 2016 10/03/16 BARGAIN François

VDF

H

F

F

H

PVDF

PVDF-based semi-crystalline polymers 2/16


VDF

H

F

F

H

α phase PVDF

β phaseStretching

TGTG TTTT

PVDF-based semi-crystalline polymers

P(VDF-co-TrFE)

2/16


VDF

H

F

F

H

F

F

H

FH

F

F

H+

VDF TrFE

α phase PVDF

β phaseStretching

TGTG TTTT


P(VDF-co-TrFE)

2/16


Ferroelectric (FE) Phase

VDF

H

F

F

H

F

F

H

FH

F

F

H+

VDF TrFE

α phase PVDF

β phaseStretching

μ

c

b

TGTG TTTT


P(VDF-co-TrFE)

2/16



VDF

H

F

F

H

F

F

H

FH

F

F

H+

VDF TrFE

α phase

Ferroelectricity

PVDFβ phase

Stretching

μ

c

b

Piezoelectricity

d33 = - 20 pC/N

Pr = 60 mC/m2

Ec = 50 V/µm

TGTG TTTT

Polarization displacement


P(VDF-co-TrFE)

2/16



VDF

H

F

F

H

F

F

H

FH

F

F

H+

VDF TrFE

α phase

Ferroelectricity

PVDFβ phase

Stretching

Paraelectric (PE) Phase

μ

c

Curie Transition

b

Piezoelectricity

d33 = - 20 pC/N

Pr = 60 mC/m2

Ec = 50 V/µm

TGTG TTTT

Polarization displacement

Applications in printed organic electronics 3/16


Ferroelectric

Direct piezoelectric

Inverse piezoelectric

Ferroelectric memories

Sensors

Actuators

Manufacturing thin, light and flexible devices… …using ink-jet printing, press-printing…

keyboards

speakers

smart labels

From polymer solution to electroactive film 4/16


T (°C)

TCurie

80

130

TMelting

25

Melt





1 Spreading

T (°C)

TCurie

80

130

TMelting

25

Melt



1



1 2 EvaporationSpreading

T (°C)

TCurie

80

130

TMelting

25

Melt



1 2



Annealing1 2 3EvaporationSpreading

T (°C)

TCurie

80

130

TMelting

25

Melt



1 32



Annealing Poling1 2 3 4EvaporationSpreading

E

E = 150 V/µm

T (°C)

TCurie

80

130

TMelting

25

Melt



1 32 4



Annealing Poling1 2 3 4EvaporationSpreading

E

E = 150 V/µm

Applications

T (°C)

TCurie

80

130

TMelting

25

Melt



1 32 4

Motivations for organic electronics 5/16


Lot of studies have been done on annealed andstretched films obtained from solvent or from themelt.

An intermediate phase with a tilt has also beenobserved for 50-60 VDF mol %

Tashiro et al, Polymer, 1986

FE CL PE






FE CL PE

Our work focuses specifically on isotropicsolvent-cast samples to be close to printed organic electronics applications






FE CL PE

Understanding the crystalline and morphological changes upon annealing andpoling steps

Our work focuses specifically on isotropicsolvent-cast samples to be close to printed organic electronics applications

5 µm

Morphology and crystalline organization 6/16

1-10 m

0.1-1 nm

SpherulitesSEM

Crystalline lamellaeSAXS

Crystalline cellWAXS


Spherulite size Inter-planar distances dhkl

Crystallinity χc

Long period LP

Electronic contrast

LP = 2π/q 2dhklsinθ = λ

10 nm

Simultaneous SAXS-WAXS experiments

Pierre PanineGrenoble, FRANCE

7/16

Solvent-cast samples of 20 µm thickness poly(VDF-co-TrFE) 70/30 mol %

Collaboration with:




7/16


Collaboration with:


25

130

T(°C)

Time

1°C/min

hot stage



DSAXS 1-2 m

DWAXS 10 cm

1 SAXS and 1 WAXS image /min

7/16


Collaboration with:


25

130

T(°C)

Time

1°C/min

hot stage

Simultaneous acquisition

SAXS on solvent-cast sample 8/16


0.1 0.2 0.40.3 0.5 0.80.70.6q (nm-1)

Heating

Cooling

T(°C)

ANNEALING 10 min



0.1 0.2 0.40.3 0.5 0.80.70.6q (nm-1)

Heating

Cooling

T(°C)

LP = 38 nm

LP = 15 nm

LP = 30 nm

ANNEALING 10 min



0.1 0.2 0.40.3 0.5 0.80.70.6q (nm-1)

Heating

Cooling

T(°C)

LP = 38 nm

LP = 15 nm

LP = 30 nm

Increase of the long period from 15 nm to 30 nm

ANNEALING 10 min

WAXS on solvent-cast sample 9/16


T(°C)

Heating

Cooling

ANNEALING 10 min



T(°C)

FE

PE

FE + DFE

Heating

Cooling

FE Phase

PE Phase

FE

DFE

ANNEALING 10 min

PE

TC

TC

Orthorhombic symmetry

Hexagonal symmetry



T(°C)

FE

PE

FE + DFE

Heating

Cooling

FE Phase

PE Phase

FE

DFE

ANNEALING 10 min

PE

TC

TC

Orthorhombic symmetry

Hexagonal symmetry

Appearance of a second crystalline phase after an annealing step in the PE phase. It coexists with the FE phase at RT and we named it DFE (Defective Ferroelectric) phase

Evolution upon temperature cycle (WAXS & DSC) 10/16


χC (%)

Heat Flow

Inter-planar distance (nm)

Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

Curie transition

Curie transition

Time

30 °C 130 °C 30 °C



χC (%)

Heat Flow


Area peaksratio

An

ne

alin

g 1

0 m

in 1

30

°C

HEATING COOLING

130 T (°C)

FEFE

PE PEDFE

25 %

45 %

Curie transition

Curie transition

Time

30 °C 130 °C 30 °C

Model 11/16

Two main conclusions : - crystallisation in the PE phase upon heating- appareance of the DFE phase upon cooling


Model 11/16



Formation of FE crystals duringsolvent evaporation

Part of chains with gauchechemical defects are expelledfrom the FE crystals and stayed atthe interface crystal/amorphous

Model 11/16





Trans and gauche conformationsare allowed in conformationnalydisorder PE phase

Crystallization of defective partof chains at the border of PEcrystals

Model 11/16





Trans and gauche conformationsare allowed in conformationnalydisorder PE phase

Crystallization of defective partof chains at the border of PEcrystals

Part of PE phase transitsdiscontinuously to FE phaseat TC

Part of PE phase transistscontinuously to DFE phase

Influence of poling on annealed sample 12/16


70 %FE

Annealed sample

Annealed and poled sample

5 %DFE

95 %FE

30 %DFE

WAXS (25 °C)



ΔHC : 17 J/g 25 J/g ΔHm : 30 J/g constant

Increase of the FE phase content No change in the PE phase content

FE + DFETC

PE Melt

FE

Tm

70 %FE

Annealed sample


5 %DFE

95 %FE

30 %DFE

WAXS (25 °C) DSC (10 °C/min)

PE Melt



ΔHC : 17 J/g 25 J/gΔHm : 30 J/g constant

Increase of the FE phase content No change in the PE phase content

FE + DFETC

PE Melt

FE

Tm

Poling treatment induces the transition of the DFE phase to the FE phase

70 %FE

Annealed sample


5 %DFE

95 %FE

30 %DFE

WAXS (25 °C) DSC (10 °C/min)

PE Melt

Model: evolution with annealing and poling 13/16


14/16


The DFE PE phase transition

The phase transition between the DFE phase and the PE phase has also been studied:

14/16




Evolution of orthorhombic symmetry (DFE) to hexagonal symmetry (PE)

Continuous evolution of inter-reticular distance (a and b cell parameters) withtemperature due to the progressive change of trans in gauche conformations

Correlated behavior between DFE peak’s position and peak’s width

14/16







Modulation of the temperature range of the transition according to annealing procedure.

The phase transition can occur before or during the Curie transition (FE to PE)

Good correlation between different experiments: WAXS, SAXS, DSC, FTIR and DMA

14/16







Modulation of the temperature range of the transition according to annealing procedure.

The phase transition can occur before or during the Curie transition (FE to PE)

Good correlation between different experiments: WAXS, SAXS, DSC, FTIR and DMA

Article in reviewBargain François, Panine Pierre, Domingues Dos Santos Fabrice, Tencé-Girault Sylvie. Polymer.

Conclusion and perspectives 15/16


Understanding changes occuring during annealing and poling steps to improveelectroactive properties of poly(VDF-co-TRFE) films for organic electronicsapplications

Studying the thermal phase transition between the orthorhombic DefectiveFerroelectric (DFE) phase and the hexagonal Paraelectric (PE) phase

Understanding the role of defects in PVDF-based copolymers to developmaterials with interesting electro-active properties

Thank you for your attention

Questions ?

16/16


structural evolutions in electroactive poly(vdf-co-trfe...

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