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Christophe Schatz,1 Jean Paul Chapel21 Laboratoire de Chimie des Polymères Organiques (LCPO), Bordeaux 2 Centre de recherche Paul Pascal (CRPP), Bordeaux

• Polymer assembly in solution : 

Strong & weak polyelectrolyte complexes

BertrandGarbay

EmmanuelIbarboure

Jean‐FrançoisLe Meins

OlivierSandre

ChristopheSchatz

ColinBonduelle

ElisabethGaranger

AngelaMutschler

AmélieVax

SébastienLecomman‐

doux

*

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Polyelectrolyte complexes in solution

polycation polyanion

complexcounterions

Applications of polyelectrolyte complexes

Fabrication of thin organic films by the Layer‐by‐Layer method

Science 1997, 277, 1232

Particles of DNA/polycation complex for gene delivery

Polymers 2011, 3(3), 1215‐1242

(An excess of polycationfacilitates the cell internalization)

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Strong vs. weak polyelectrolyte complexes

+ ==‐ + ‐

‐‐‐

‐ ‐‐‐‐ ‐ ‐‐‐

‐

++ +

+

+

++

+ +

++

+

+++

‐

+

++

++ +

+ ++++

++

++

+

+

‐ ‐ ‐‐‐

‐‐‐‐‐

‐ ‐‐ ‐‐

polyanion‐‐‐‐‐ ‐ ‐ ‐

‐‐‐‐

‐‐‐‐+

++ +

++ +

++

+++ +

+

++

+ +

+++

+ +

++

+

+

++

+

+

+ ‐

‐‐‐ ‐

‐‐‐‐‐

‐ ‐

‐ ‐‐

‐

‐‐

‐‐ ‐‐‐‐

‐

‐‐ ‐

‐‐+

+ ++

+

++

+

+++

+‐+‐+

++

+ ‐‐+

LiquidÆsolid transitionPRECIPITATION

LiquidÆliquid transitionCOACERVATION

‐

++

‐‐‐ ‐+

+

+

+

+ ‐

‐‐‐‐ ‐

+‐

polycation

Strong vs. weak polyelectrolyte complexes

• Morphology scattering

• Thermodynamics microcalorimetry

• Kinetic stopped flow

Notre ‘marque’ c’est mkt

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Morphology of strong complexes(in dilute conditions)

Linear polyethyleneimine (LPEI)Mw = 2 kDapka ~ 7

Sodium polystyrene sulfonate (NaPSS) Mw = 4.3 / 32 / 150 kDapKa ~ 1.8

Addition of LPEI in NaPSS (pH 3)

charge ratioZ (+/‐)

precipitation PhD Marie Haddou 2019

Morphology of strong complexes

Static and Dynamic light scattering

Very small particles of complex (complexes I) coexist with larger aggregates (complexes II)

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Morphology of strong complexesSmall‐angle neutron scattering

Complexation mechanism

Morphology of strong complexes

Atomic force microscopy : LPEI/PSS600K

PhD Marie Haddou 2019

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Morphology of weak complexes (dilute conditions)

Polyacrylic acid (PAA)Mw = 2 kDapka ~ 6

Poly(diallyldimethylammonium chloride)(PDADMAC)Mw =50 kDa

Addition of PAA in PDADMAC (pH 10) : observation as function of Z (‐/+)

droplets of coacervatearound Z=1

Dense liquid phase (coacervate) at the bottom

Coalescence of droplets

time

Liu et al. Soft Matter 2016, 12, 9030‐9038

Formation of the coacervate phase at Z=1

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Morphology of weak complexes

1200

Static and dynamic light scattering

Transition at Z(‐/+) = 0.6

*

*

*

*

Morphology of weak complexes

Small‐angle neutron scattering

*

Liu et . Adv Colloid Interface Sci 2017, 239, 178‐186

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Morphology of weak complexes

• soluble complexes at Z < 0.6(concept of host‐guest PE)

• insoluble complexes at Z > 0.6

Z = 0.42Z = 0

Z = 0 with 10 mM NaClZ = 0.67 Z = 1.6

Disproportionationat Z ~1

neutral complex Coagulation Æ coacervate

colloidalparticle

more charged complex

Analysis of the dense liquid phase (coacervate*)

* Water content : 75 wt.%

heterogeneities

network structureOrnstein‐Zernike: S(q) = S(0)/(1+q2ξ2)ξ = 1.5 nmξ = 1.2 nm

correlation peak (q*)pseudo‐nematic orderξ* = 1.5 nmξ* = 1.2 nmξ* = 3.8 nm

Lorchat et al. EPL, 106 (2014) 28003

polyelectrolyte peak

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Thermodynamics of complexation

Isothermal Titration Calorimetry

Sensitivity : ~µJ• Integration of the total heat releasedÆ 'H

• Fitting the titration curveÆ Kd

• 'G = - RT ln Kd

'G = 'H-T'SÆ 'S

Thermodynamics of complexation

0.0 0.5 1.0 1.5 2.0 2.5 3.0

‐6E3

‐4E3

‐2E3

0

2E3

'H(J/

mol of titran

t)

Z[+]/[‐]

exo

0.0 0.5 1.0 1.5 2.0 2.5‐1E3

0

1E3

2E3

3E3

4E3

5E3

6E3

'H(J/mol of titran

t)

Z[+]/[‐]

endo

Strong complexes (LPEI/PSS4.3k) Weak complexes (PAA/PDADMAC)

'H - 6.4 kJ/molT'S + 23.1 kJ/mol'G - 29.5 kJ/molK 1.5 x 105 M-1

'H + 5.7 kJ/molT'S + 24.0 kJ/mol'G - 18.3 kJ/molK 1.6 x 103 M-1

Origin of the EXO/ENDO difference ?PhD Marie Haddou 2019

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Thermodynamics of complexationEnthalpy of hydration of polyelectrolytes (PEs)

Water additionin PE solution monitored by ITC

• CoacervateH2O content > 50 wt.%

(> 5 H2O/polym.units)

Batys et al. Soft Matter2019,15, 7823‐7831

Kinetics of complexation

Stopped‐flow for rapid kinetics investigations (SFM 4000‐ Biologic, France)

Obs e rv a ti on

A

F 2

B

F1

Syringe 1 filledwithpolyanion

Syringe 2 filledwithpolycation

complexes   

DETECTION

2 individual stepping motors(asymetry ratios)

V

Dead time = V /(F1+F2)

Mixing is‐ Fast (< 5 ms)‐ Homogeneous‐ ReproducibleNo influence of the addition order!

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Kinetics of complexation : strong complexes

Wcomplexation < dead time SF

Kinetics of complexation : weak complexes

Conductimetric dectection : Æ ion‐pairing

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Kinetics of complexation : weak complexesLight scattering detection : Æ Formation of complexes

PAA/PDADMAC at # Z ratios

Kinetics of coacervation (Z=1)

exposure time : 5 ms

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Kinetics of coacervation (Z=1)

ID02 ‐ ESRF

Coagulation theory

Smoluchowski

~t1/3

Takahashi et al. J. Phys. Chem. Lett. 2017, 8, 737−741

Light scattering – Mie theory

90° (scattering)180° (extinction)

0.001 0.01 0.1 1 10 100

0.0

0.2

0.4

0.6

0.8

1.0

I (no

rmal

ized

- a.

u.)

time (s)

Influence of the mixing time

• Strong complexes (LPEI/PSS)

Z Z

dispersity

Fast addition of LPEI in PSS

• # mixing methods = # mixing times

size

Slow addition of LPEI in PSS

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Influence of the mixing time

• Weak complexes (PDADMAC/PSS)

PAA in PDADMAC PDADMAC in PAA

• Order of addition • Stopped flow mixing

Intensity

(a.u)

Æ Equilibrium structures

ACKNOWLEDGEMENTS

LCPOE. IbarboureM. Haddou

CRPPJ.P ChapelJ. GiermanskaL. XiaooqingC. Pucci

LLBF. CousinJ. Jestin

ILLI. GrilloL. Porcar

PANORAMA (2014‐17) CRPP, LCPO,MSC & LLB

Fundings

LIPHYI. Morfin

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Thank you for your attention

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