Salt-Polymer Interaction in Concentrated Salt Dispersion

Center for Particulate & Surfactant Systems (CPaSS)IAB Meeting New York, NY

August 20th, 2009

XIAOHUA FANG

Columbia University

Possible Interactions in a Dispersion System

Na+

CO32-

Salt/Surfactant

Polymer/Surfactant

Polymer/Salt

Na+

CO32-

Surfactant Mixture

Step II: Understand 2-component systems

Multi-component systems

Step III:Understand 3-component systems

Crystals of Salt

Na+CO32-H2O

Step I: Figure out components in the system

Ionic surfactant Nonionic surfactant Polymer backbones Electric Charges

Introduction

• Challenges in real formulations containing high salt concentration.– Homogenous or dispersed – Stable with time or temperature– Pourable in a wide range of temperature

•

– Low salt concentration range charge screened; polymer collapsed, etc.

– Ultra-High salt concentration, morphology of polymer chain and its function?

The interaction of polyelectrolyte and salt Coil-Collapse-Re-expansion

Materials/Methods

*Salt-Polymer Interactions

Density

Light Scattering

Conductivity

Rheometry

•Materials

•Methods

*Sodium carbonate(Soda Ash) *Polyacrylic acid

*Water * Other additives

*Water related Interactions

Water Activity

Radius of Gyration in concentrated salt solution

0 5 10 15 2040

60

80

100

120

140

160

Rad

ius of

Gyr

atio

n (n

m)

Salt Concentration (wt%)

Rg grows exponentially with salt level increase in entanglement Concentration

Hydrodynamic Radius in salt solution

0.0 0.5 1.0 1.5 2.0 2.5

0

500

1000

1500

2000

2500 0% salt,(4M) PAA 5% salt,(4M) PAA 20% salt,(4M) PAA

Hyd

rody

nam

ic R

adiu

s(nm

)Polymer Concentration (mg/ ml)

Sodium Carbonate Concentration

0.0 0.5 1.0 1.5 2.0 2.5

0

500

1000

1500

2000

2500

Sodium Carbonate Concentration

Polymer Concentration (mg/ ml)

Hyd

rody

nam

ic R

adiu

s(nm

)

0% salt,(1M) PAA 5% salt,(1M) PAA 20% salt,(1M) PAA

At higher salt level, PAA molecules oscillate within a larger effective region.RH increases with polymer concentration after a certain threshold PAA level.

Ion Condensation on Polymers

0 5 10 15 20-2.0

-1.5

-1.0

-0.5

0.0

0.5

30405060708090

100

20% Salt 2K 450K 1M 4M5% Salt 2K 450K 1M 4M0% Salt 2K 450K 1M 4M

Con

duct

ivity

(ms)

PAA Concentration (mg/ ml)

Ion condensation happens and the salt species condensed onto PAA chains.

Larger molecules are more effective in holding salts than smaller chains.

Low Mw

High Mw

Speculation---Concentration Dependence

No Salt High Salt

Higher Salt Level More Rheological Sensitivity to PAA Concentration

0 100 200 300 400

0

10

20

30

40

50

Mw=450k, 0% salt,0.2mg/ ml PAA Mw=450k, 0% salt, 20mg/ ml PAA Mw=450k, 20% salt, 0.2mg/ ml PAA Mw=450k, 20% salt, 20mg/ ml PAA

Vis

cosi

ty (D

/cm

2 )

Shear Rate (1/ Sec)

50 100 150 200 250 300 350 400 450

0

500

1000

1500

2000 0% salt,0.1mg/ ml(4M)PAA 0% salt,20mg/ ml(4M)PAA 20% salt,0.1mg/ ml(4M)PAA 20% salt,20mg/ ml(4M)PAA

Vis

cosi

ty(D

/cm

2 )Shear Rate (1/ Sec)

Viscosity increases with PAA concentration at all salt levels.At high salt level, the increase in viscosity with PAA concentrationis more significant.

0 50 100 150 200 250 300 350 400 4500

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

0% salt, 20mg/ ml(4M)PAA,25oC

0% salt, 20mg/ ml(4M)PAA,45oC

20% salt, 20mg/ ml(4M)PAA,25oC

20% salt, 20mg/ ml(4M)PAA,45oC

Vis

cosi

ty(D

/cm

2 )Shear Rate (1/ Sec)

Higher Salt Level More Rheological Sensitivity to Temperature

0 50 100 150 200 250 300 350 400 4500

50

100

150

200

250

300

350

400

0% salt, 20mg/ ml (450k)PAA,25oC

0% salt, 20mg/ ml (450k)PAA,45oC

20% salt, 20mg/ ml (450k)PAA,25oC

20% salt, 20mg/ ml (450k)PAA,45oC

Vis

cosi

ty (D

/cm

2 )

Shear Rate (1/ Sec)

Viscosity decreases with temperature at all salt levels.At high salt level, the decrement in viscosity with temperatureis more significant.

Small Molecule

Large Molecule

Schematic Diagram of Salt Ions Localization

Low Temperature High Temperature

Temperature

Concluding Remarks

1. is unfolded and more hydrated.

2. plays a more dominant role on the rheological behavior of the system.

3. holds more salt locally.

• As salt level increases, PAA

• Larger molecules are more efficient in holding ions locally.

Future Plans

1. Conduct light scattering, rheological, conductivity measurements on multi-component system.

2. Elucidate the overall mechanism by which dispersion and flow properties are controlled in the system.

•NSF-Industry/University Cooperative Research Center

•All the Industrial Collaborators

We owe great thanks to: