Presented Nov. 2014 at AIChE meeting. Examines the use of polyelectrolyte complexes for surface modification in consumer products such as cleaners. Summarizes synthesis and characterization of stable complexes in solution via light scattering. Illustrates characterization of adsorbed layers of complexes on germanium and silica surfaces via Fourier Transform Infrared spectroscopy and gravimetry via a quartz crystal microbalance.

1. Quantifying Adsorption of Surfactants and
Polyelectrolyte Complexes at the Solid-Liquid
Interface by Quartz Crystal Microgravimetry with
Dissipation (QCM-D)
Phase Behavior and Characterization of Polyelectrolyte
Complexes (PECs)
AIChE Meeting – November, 2014
D.R. Scheuing
Clorox
Mona M. Knock
Advanced Measurements Sciences
Mike Kinsinger, David R. Scheuing
Advanced Technology
Clorox Technical Center, Pleasanton CA
ANA 1.1 / S&D 1.2 #42420; May 2, 2011

2. Outline
What Are PECs & How To Make Them
What Can PECs Do?
PECs in the Consumer Packaged Goods Industry
Characterization of PECs in Solution
Characterization of PECs on Surfaces
2

3. PECs Are Self-Assembling Aggregates of Oppositely Charged Polymers
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Ladder – Molecular
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or
Scrambled Egg -
Multiple Chains in
Particle
Ref. 1,2,6
Driving Force – Entropy Gain From Release of Small Counterions

4. PEC Formation Requires Balance of Entropic and Electrostatic
Energy Contributions
Entropic part –
• Small Entropy loss due to restrictions on polymer chains
• Large Entropy gain from release of small counterions
Electrostatic –
• Favors close association of PE charges in a phase
• Phase Separation and/or Precipitation Favored
• Stop Phase Separation at Colloidal Dimensions Yields Stable Particles
Let’s define “R” = moles
(equivalents) of cationic
charges/moles (eq) of
anionic charges –
R= +/-
Non-Stoichiometric PECs Are
Stabilized By the Electrostatic
Charges of Excess Component

5. PEC Synthesis in Aqueous Systems – Driven By Chain Dynamics
Polymer type – Strong Acid (styrene
sulfonate), Strong Base (DADMAC quat)
5
Little pH Dependence
Polymer type – Weak Acid (acrylic,
methacrylic acid), Weak Base (chitosan,
ethyleneimine )
Major pH Dependence
PECs Made in Pure Water – “Frozen” Non-Equilibrium Structures
PECs Made in Water + Electrolyte – Dynamic Living Systems
High MW Chains Favored, Sulfonates Displace Carboxylates 1
Assemble Stable PECs from Dilute PE Solutions !
Total Polymer – 0.01 – 0.1 wt% , or < 10 (meq/l or mM) of total charges 1,10

6. Synthesis of systems in this talk
6
All made in 20 ml vials with stirbar @ 600 rpm
Rapid additions of small volumes, low viscosities = rapid mixing regime
Aqueous Diluent
Aqueous stock –
polymer “A” in molar
(charge equivalents)
deficiency
Aqueous stock –
polymer “B” in molar
(charge equivalents)
excess
Polymer A solution
@ 0.1 – 10 mM
PEC of B/A
@ 0.2 – 20 mM

7. What Can PECs Do?
Flocculants 1,2
Specialized
Membrane
Production 1,2
7
PECs with DNA –
Gene Therapy 4
Drug Delivery 3
Cartilage
Mimics, 5
PECs Layers on Particles – Sensors, Protein
Immobilization 7,8
See Also –
Prof. M. Tirrell group
http://tirrell.ime.uchicago.edu/
PECs Layers on Hard Surfaces –
Hydrophilic/Hydrophobic Surface
Modification 9

8. PECs in the Consumer Packaged Goods (CPG)
Cleaners Industry – Why?
Inherently low actives approach to surface treatment
and modification
Formulation cost/performance - $$
Consumer perceptions – Less “chemicals” in the home
Enabler for sustainability – naturally derived polymers from waste
biomass
Producers (CLX) and retailers (Wal-Mart) have public sustainability goals
8
Bottom Line
Products must perform for consumers – with good perceived
value
http://corporate.walmart.com/global-responsibility/
environment-sustainability/
sustainability-index
http://www.thecloroxcompany.com
/corporate-responsibility/

9. Characterization of PECs in Solution
9

10. Characterization Via Static Light Scattering
Multi-Angle Light Scattering (MALS) in
Batch Mode
Simultaneously obtain:
• Absolute Molecular Weight (Mw)
• Second Virial Coefficient (A2)
• RMS Radius (Rg)
c = Concentration of Solute
Excess Rayleigh Scattering
As Function of Angle and
Concentration
Angular
Dependence of
Scattered Light –
Yields RMS
Radius of
Aggregate
Weight Average
Molar Mass
2nd virial
coefficient
Optical
constant
*Wyatt Corp.
*
Debye Plot

11. Chitosan/Poly(acrylic acid) PECs
Chitosan
Natural, edible, bacteriostatic, cationic PE at “low” pH
Derived from waste biomass – shrimp/crab shells
Poly(acrylic acid)
Grades available for use in cleaners of food-prep surfaces
(EPA)
Cationic Amine
groups for interaction
electrostatic binding
with PAA
Chitosan – weak base PE – water soluble only at pH < 6.
Readily Soluble as citric acid salt @ pH 2.0
Poly(acrylic acid) – weak acid PE. Well below pKa @ pH 2.0.
Will Chitosan/PAA PECs form at low pH?

12. Static Light Scattering Confirms PEC Formation at Acidic pH and
Presence of Multiple Polymer Chains in Each PEC
PECs MW = 4 million !
Polymers are about 60K each
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
4.0M
3.5M
3.0M
2.5M
2.0M
1.5M
1.0M
(g/mole)
w
500.0k
0.0
M
Amine/Acid Ratio
R = Chitosan/PAA – 2mM Total Polymer
pH = 2.2, [Citric Acid] = 0.7 %

13. Dynamic Light Scattering Measures the Correlation Curve
– Size is Calculated
13
2 1 2 g (q, ) 1 [g (q, )]
( , ) exp( ) 1 g q   
t q D 2  
Monodisperse particles
Decay rate
Diffusion
coefficient
Gaussian Distribution of Diffusion
Coefficients – Use “Cumulants Method” to
Fit Decay
Z – average
Diffusion
Coefficient
Polydispersity
Index (PDI)
Z-average Size Is Intensity-Weighted – Because Intensity Is Measured
If PDI <0.5 – Compare Z-average directly
If PDI >0.5 – Compare the Distributions of Samples Measured in Same Medium
*Zeta Sizer Nano Manual – Malvern Corp
*
*
*

14. Velocity of Particles in Field Measured – Zeta Potential is
Calculated
Zeta
Potential
Electrophoretic
Mobility – Velocity
of Particle
14
Folded Capillary Cell
(Malvern)
Henry’s function –
approximately =
1.5
Dielectric Viscosity
constant
Particle Motion Causes Time-Dependent Intensity
Variation of Laser Light = Frequency/Frequencies
~ Velocity Distribution
PALS = Phase Analysis Light Scattering – Read Phase Shift of
Laser Light – Better Sensitivity
Malvern Applies Clever Field Reversal Sequences to Overcome
Capillary Wall Effects (M3)
*Zeta Sizer Nano Manual – Malvern Corp
*
*

15. Size Distributions of DADMAC/PAA PECs From DLS Show Shifts with
R (DADMAC cationic equivalents/PAA acid equivalents)
15
PECs From a Strong (Quat) and Weak (Carboxylic Acid) Polyelectrolyte
pH = 10. 5
R=0.75
R=0.25
R=1.0
R=2.0
Polydispersity range = 0.063 – 0.165. Z-average diameters may be
compared.
polyDADMAC = Floquat 5240 (SNF)
Poly(acrylic acid) = Aquatreat AR-4 (Akzo Nobel)
Total polymer concentration constant 2 mM charges (2 meq/l) (< 0.025 wt%)
Poly DADMAC

16. DADMAC/PAA PECs Are “Living” Systems – Behavior Shifts
As pH Is Decreased
16
PECs Unstable
0.85 < R < 0.95, pH 7-10
PECs Are Large Near
Phase Boundary – High pH
PECs Are Smaller at
Extremes of R @ pH 7 –
10.5
At pH 3.0, PECs
crash at low R value
Triplicate measurements % RSD
< 3.0% = Symbol Size
PDI < 0.25 for all samples
Unstable, pH 3

17. Zeta Potential of + or – 30 mV Stabilizes
DADMAC/PAA PECs
17
Unstable Region, pH 7-10.5
Unstable, pH 3
PECs Unstable in
Region of Charge
Reversal
At pH 3.0 – PECs are
Cationic Even at R < 1.0.
Most Acid Groups Are
Protonated. DADMAC
charges stabilize PECs.
At pH 3.0, R=0.25, Ppt.
Formed Due to Strong
DADMAC/Acid
Interactions. Chain
Dynamics Differ From
Chitosan/PAA !
Triplicate Measurements, %RSD
<10% (error bars) for all samples

18. Chain dynamics affect PEC robustness
0% citric acid Same PAA, MW = 8,500 0.65% citric acid – 35 mM
18
diameter error bars = max %RSD observed with triplicates at each temperature

19. What Can PECs Do?
19
Surface Modification & Engineering

20. Household soil Resistance via adsorbed hydrophilic layers
g LA cos q= (g SA – g SL) Young – Dupre’
cos q= (g SA – g SL) / g LA cos q = 0 (at q =90º)
g LA = liquid oil/air tension (can measure !)
g SA = solid/air tension g SL = solid/liquid tension
g LA of oil is fixed!
Increase Solid-Oil Tension = Increase q
Adsorbed PECs + water decreases spreading
Solid
Liquid
Oil
Air
Air
Solid
q
Liquid
Oil

21. Improve soil Release with water-swollen PEC layers
Reduce Work of Adhesion Under water –
Wa = g SO – g OW – g SW
SO = solid/oil OW=oil/water SW=solid/water tensions
g OW is fixed and large (40 mN/m)
With Water-swollen PECs on Solid Surface
Solid/water tension vanishes
Match Solid/oil and Oil/water tensions
Oil release spontaneous at Wa = 0 !
Adsorbed PEC layers with liquid water alter both “controlled”
tensions.
Water only “displacement” of oil possible.

22. Fourier Transform Infrared Spectroscopy with Attenuated Total
Reflectance (ATR) Sampling Optics Probes Adsorbed PECs
IRE
Air (Ge)
Sampling depth, dp= 736
nm at 1650 cm-1
Refractive index = n2 = 1.5
dp = l/2p (sin2 q  n21
2 )1/2
Refractive index = n1=
4.0
q
n21=n2/n1

23. Commercial Optics Enable Controlled Exposure of a Ge
Surface to PECs Solutions
50 mm
Trough on Horizon rig
Dry Nitrogen/Air
Input
2.5 mL trough
Images of “Horizon”
from Harrick, Inc.
PECs Solution

24. DADMAC/PAA PECs Adsorb on Anionic Ge Surface at
both R>1 and R<1 – and Hydrate in Air Readily
Total Polymer Concentration – 1.7mM, pH 12.0, electrolyte = 0.12% NaCl,
5 minutes adsorption time

25. FT-IR Band Shifts Indicate Water Uptake Swells Adsorbed
DADMAC/PAA Layers – Polymer Chain Dynamics Persist
25
Carboxylate Bands (PAA) Shift Due to Increase in Distance To
DADMAC Quat Group “Counterion” 11. Water Uptake Obvious.

26. FT-IR spectra of Chitosan/PAA PECs on Ge
26
Total polymer concentration = 2.0 mM, pH =2.0, 0.7% citric acid
Adsorption time = 5 min, then rinsed with 100 ml deionized water.
Adsorbed layers under
dry nitrogen purge

27. FT-IR spectra characterize adsorbed layers of
Chitosan/PAA PECs
27
Water content increases with
adsorbed polymer concentration
PAA in Adsorbed layers decreases as
R increases (more chitosan in PEC)

28. PECs On Surfaces - Quartz Crystal Microbalance with
Dissipation (QCM-D) Measures Adsorption
28
Oscillating Crystal
– Silica Surface
PECs Solutions and Rinse Solutions Flow
Across Crystal @ 150 microliters/min,
Temperature Controlled at 25 ºC
*
*Q-Sense

29. 29
Quartz Crystal Microbalance with Dissipation: Solid-Liquid
Interface: Sauerbrey Relation
• crystal oscillates under applied AC voltage
• frequency (f) depends on oscillating mass, including
coupled water
• f decreases when thin film attached to crystal
• f decrease proportional to film mass, if film thin & rigid
• film mass (m) calculated by Sauerbrey relation:
Δm =  Δf C / n
• C = 17.7 ng Hz-1 cm-2 for a ~5 MHz quartz crystal
• n = 1,3,5,7,9,11 is the overtone number
Here, we use the Sauerbrey model, as our films are not viscoelastic.

30. Net Cationic PECs Adsorb on Silica and Resist Rinsing with
Brine
30
NaCl
Rinse
Water
Rinse
Multiple Adsorption/Water
Rinse
Initial Maximum
Adsorption
201 ± 26 ng/cm2
After NaCl Rinse
133 ± 20 ng/cm2
Total Polymer Concentration = 1.5 mM, pH =11.0, 20mM NaCl.
Flow rate constant at 150 microliters/minute

31. Net Anionic PECs Adsorb on Silica – And Show Dynamic
Responses to Rinses
31
NaCl
Rinse
Water
Rinse
Multiple Adsorption/Water
Rinse
Total Polymer Concentration = 1.5 mM, pH =11.0, 20mM NaCl
Initial Adsorption
398 ± 43 ng/cm2
After Water Rinses
235 ± 42 ng/cm2
After NaCl rinse
146 ± 47 ng/cm2

32. Adsorbed Amounts of PECs Converge Only After Extensive Rinsing.
Net Anionic PECs Differ in Chain Dynamics from Net Cationic PECs
32
Sauerbrey relation
was maintained for
both samples !

33. Summary
Polyelectrolytes of opposite charge can form PECs due to the overall
entropy gain from loss of small counterions
PECs can be assembled in dilute solutions and stabilized by the
charge of the polymer in excess
33
Static and Dynamic Light Scattering Can Be Readily Applied to
Characterization of PECs at < 5 mM total polymer concentrations.
PECs with diameters of 50 – 250 nm with zeta potentials of 30 mV (+ or
-) are found to be quite stable in solution
FT-IR spectroscopy with ATR optics confirms that PECs designed to
have living chain dynamics adsorb rapidly onto surfaces.
QCM-D can measure PECs on surfaces near 100 ng/cm2.
Confirmation of anionic PECs adsorbing on anionic surfaces due
to dynamic chain re-arrangements is also obtained.

34. Thanks !
Clorox
You –
The Audience and Consumer !
34
Dr. Mona Knock – QCM-D data
Dr. Charles Scales – SLS data

35. References
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1. Dautzenberg, H. in Surfactant Science Series #99 - Physical Chemistry of Polyelectrolytes, Chap 20, Marcel Dekker,
2001
2. Michaels, A.S., Miekka R.G. J.Phys.Chem. 1961, 65(10), 1765-1773(a)
3. Martin Müller, Bernd Keßler, Johanna Fröhlich, Sebastian Poeschla and Bernhard Torger ,Polymers 2011, 3, 762-778;
doi:10.3390/polym3020762
4. Alexander V. Kabanov ,Victor A. Kabanov , Advanced Drug Delivery Reviews 30 (1998) 49–60
5. Haifa H. Hariri, Joseph B. Schlenoff, Macromolecules DOI: 10.1021/ma101297
6. Katja Henzler,Bjorn Haupt,Karlheinz Lauterbach, Alexander Wittemann, Oleg Borisov, Matthias Baliauff J.AM.CHEM.
SOC. 2010, 132,3159-316
7. G.Decher, M.Eckle, J.Schmitt,B.Struth, Current Opinion in Colloid Interface Science, 1998, 3 (1), 32-39
8. G.Decher, B.Lehr,K.Lowack,Y.Lvov,J.Schmitt Biosensors Bioelectronics 1994, 9:677-684
9. Quantifying Adsorption of Surfactants and Polyelectrolyte Complexes at the Solid-Liquid Interface by Quartz Crystal
Microgravimetry with Dissipation (QCM-D), Mona M.Knock, Mike Kinsinger, D.R.Scheuing, presented at AOCS
meeting 2011, ANA 1.1 / S&D 1.2 #42420
10. Heide-Marie Buchhammer, Mandy Mende, Marina Oelmann, Colloids and Surfaces A: Physicochem. Eng. Aspects
218 (2003) 151-159
11. J.Umemera, H.H.Mantsch,D.G.Cameron J.Colloid Int.Sci. 83 (2) 558 (1981)