Ionic polysaccharides, solubility, interactions with surfactants, particle formation, and deposition Björn Lindman, Tommy Nylander, Maria Miguel and Lennart Piculell Physical Chemistry 1, Lund University, PO Box 124, 221 00 Lund, Sweden and Chemistry Department, Coimbra University, Portugal Bjorn.lindman@fkem1.lu.se

Polymer + Surfactant ubiquitous in formulations

1.  Complementary Cleaning + thickening, stabilisation, redeposition

2. Synergistic Thickening (general) Deposition (hair-care)

Polymer-Surfactant interactions may be

1.  Repulsive Homogeneous solution

Segregative phase separation

2. Attractive (electrostatic, hydrophobic)

Complex formation Associative phase separation

POLYELECTROLYTE EFFECTS

•  A polyelectrolyte in aqueous solution dissociates into 1 polyion and n counterions; typically n >> 1

•  a large no. of particles: large ΔSmix

•  thus high solubility

•  If the counterions mix into a phase, the polyion has to follow (condition of electroneutrality)

• Divalent and multivalent counterions different

Polymer solutions (as rheological modifiers)

Na Cl

Entanglements Extension

Spherical Surfactant Micelle

Counterion entropy

+

+

+

+

+

+

+

Counterions

+ + +

+ +

+

+ +

+ +

+

+ + +

+ + +

+ +

+ +

+

- -

- - -

- - -

- - - -

- -

- - - - -

- -

- 60-80% Counterion Binding

CSURFACE >> CBULK ΔS < 0

Unfavorable ΔG > 0 High CMC

Salt decreases CMC

Network formation and gelation

•  A gel contains at least two components, one solid-like and one liquid-like, where both are continuous throughout the gel.

What are polyelectrolyte gels?

•  Polymer network with charged groups: counterion entropy gives swelling (up to 1000 times or more)

Counterion entropy gives repulsion between surfaces

Polyelectrolyte adsorption ���Case I: Polymer and surface have opposite charge

Add salt

Entropic gain of counterions

Adsorption���decreases

a

Case II: Polymer and surface have the same charge

+

+

+ - - -

+ + + - - - - - - - - - - - - - - - -

+

+ +

-

-

-

+ + + -

- -

+ + +

- -

+

+ + -

-

+ +

+

+

+ -

Add salt Adsorption increases

+ -

+

+

+ - - -

+ + +

- - - - - - - - + + +

- - - - - - - -

Entropic loss of counterions + -

+ -

Solvent Polymer

Surface

Aqueous systems: Adsorption occurs since water interacts unfavorably with polymer (clouding polymer) or surface (hydrophobic surface)

Solvency effects

Deposition/adsorption depends on an interplay between different interactions

In a mixed solution

Interactions between cosolutes are:

Repulsive (most common)

or

Attractive (electrostatic, hydrophobic - not hydrogen-bonding in water)

Depending on interaction

Segregation

Association, or

Miscibility

An amphiphilic polymer: DNA Self-assembly: Double Helix

Driven by hydrophobic association not H-bonding. Opposed by electrostatic repulsion: Limits self-assembly. (Dissociation without electrolyte)

Another controversy: Cellulose

Polymer-Surfactant Association: pearl-necklace model

•  Cooperativity

Polymer-Surfactant Interaction

•  Surfactant micellization induced by polymer

Hydrophobic association is always essential to the interaction

When do surfactants bind to polymers?

Ionic Surfactants

self-assembly induced by polymer

mixed micellization

All Surfactants Hydrophobically modified polymers

Oppositely charged polymers

Non-ionic polymers

Experimental cmc and cac data

Cac for different polyelectrolytes and alkyltrimethylammonium bromides

For nonionic P cac much larger: lowering of cmc up to a factor of 5

Network formation and gelation

•  A gel contains at least two components, one solid-like and one liquid-like, where both are continuous throughout the gel.

What are polyelectrolyte gels?

•  Polymer network with charged groups

polymer network polymer network + hard spheres

Separation of the different contributions to the pressure

+ hard spheres

polymer network + hard spheres

Polymer network + hard spheres + charges

Separation of the different contributions to the pressure

+ charges

polymer network polymer network + hard spheres

Polymer network + hard spheres + charges

Separation of the different contributions to the pressure

+ hard spheres

+ charges

0.0

0.50

1.0

1.5

2.0

0.0001 0.001 0.01 0.1

P/! k

BT

"/2

Result

polymer network

polymer network + hard spheres Polymer network

+ hard spheres + charges

network packing fraction

0.0

0.50

1.0

1.5

2.0

0.0001 0.001 0.01 0.1

P/! k

BT

"/2

Result

polymer network

polymer network + hard spheres Polymer network

+ hard spheres + charges

network packing fraction

0.0

0.50

1.0

1.5

2.0

0.0001 0.001 0.01 0.1

P/! k

BT

"/2

Result

polymer network

polymer network + hard spheres Polymer network

+ hard spheres + charges

network packing fraction

•  Due to the requirement of macroscopic electro-neutrality,

counterions are confined to the network 2 contributions to the pressure

•  Osmotic pressure exerted by the confined ions •  Coulomb interaction (attractive and repulsive)

•  Due to the requirement of macroscopic electro-neutrality, counterions are confined to the network 2 contributions to the pressure

•  Osmotic pressure exerted by the confined ions •  Coulomb interaction (attractive and repulsive)

•  Separation of the two contributions Confined counterions increase the pressure Coulomb interactions reduce the pressure

Gel Swelling Experiment: How & Why

=> Potential ”responsive gels” (drug delivery, water retention…) => Info on interactions between gel & additive

water water + additive

water + more additive

• Make gel pieces of cross-linked polymer • Immerse gel pieces in series of solutions with increasing conc of additive

Polymers Used in Gels Commercial cellulose derivatives cross-linked by divinylsulfone •  HEC (hydroxyethyl cellulose) •  HMHEC •  cat-HEC (”JR400”) •  cat-HMHEC (”LM200”)

O H Cl

C H 3

C H 3 R N +

O C H 2 O C H 2 C H 2 O H

O H O H O

O H O H O

C H 2 O ( C H 2 C H 2 O ) 2 C H 2 C H C H 2

τ 1-τ JR-400 : R=CH 3 τ =45mol% Mw ≈ 500000 LM-200 : R=C 12 H 25 τ =9mol% Mw ≈ 100000

General Swelling Isotherm for ”Weakly Hydrophobic” Nonionic Gel

with Ionic Surfactant

5 10 15 20 25 30 35

0.1 1 10 100

V/V 0

C f,SDS 0 cac

HEC gels swollen in alkyl sulfate solutions Sjöström & Piculell Langmuir 17(2001)3836

Gel Swelling Experiments Detect Surfactant Binding

0

50

100

150

200

0.1 1 10 100

V /

m (

ml/g

)

c (mM)

SHS STS SDS SDeS SOS

0

CMC:

=> HEC binds alkyl sulfates with > 8 carbon tails

Cat-HEC Gels + Different Anionic Surfactants

10

100

1000

0.0001 0.001 0.01 0.1 1 10

V /

m (

ml/g

)

c (mM) 0

STS SDS SD(EO)2S CMC:

Sjöström & Piculell Colloids Surf A 183-185 (2001) 429"

• Collapse & redissolution • Two CAC:s!? • Both correlate with CMC => both reflect surfactant self-assembly

Polysaccharide-surfactant systems. Phase separation

SEGREGATING POLYMER/SURFACTANT MIXTURES

•  In general (i.e,. in absence of electrostatic or hydrophobic attractions), effective repulsion between a polymer and a surfactant micelle is expected

•  Since a surfactant micelle is effectively a polymer, repulsion should lead to a segregative phase separation, as for mixtures of dissimilar polymers

anionic + anionic nonionic + nonionic

Nonionic polymer + nonionic surfactant Segregation

MIXTURES OF OPPOSITELY CHARGED POLYELECTROLYTE + SURFACTANT:

ASSOCIATIVE PHASE SEPARATION

•  For intrinsically hydrophilic polyions, the association is driven only by electrostatic interactions

•  Close analogy to polyelectrolyte complexes

Anionic polysaccharide + Cationic surfactant

Association

Nature of conc phase: conc soln/gel, liq crystal, solid crystal

Generic phase diagram for oppositely charged mixtures

Thalberg et al.

The mesophases

Azat Bilalov, Physical Chemistry, Lund University, e-mail: azat.bilalov@fkem1.lu.se

Thalberg et al.

Effect of salt on polyelectrolyte + ionic surfactant

Low salt Association

Intermediate salt Miscibility

High salt Segregation

• First increase in turbidity due to phase separation above CAC

•  Then onset of redissolution at free surfactant concentration < CMC

0

0.02

0.04

0.06

0.08

0.1

0.001 0.01 0.1 1 10 100

Abso

rban

ce

SDS concentration (mM)SDS concentration (mM)

1φ

2φ

1φ

Abs

orba

nce

at

λ =

500

nm

cac cac2 1:1

Phase separation and redissolution by adding SDS to dilute solution of cat-HEC

(CH2CH2O)n-CH2CHOHCH2N+(CH3)3Cl-

O

OR'

H

H

OR'

H

H

R'O

H

OO

HO

R'O

H

HOR'

H

H

O

R

n

(CH2CH2O)n-OHR=H or R'=H or

100ppm “UCARE LR-30M”

A.V. Svensson, L. Huang, E.S. Johnson, T. Nylander, L. Piculell, Appl. Mat. & Int. 1 (2009) 2431

Solvent Polymer

Surface

Aqueous systems: Adsorption occurs since water interacts unfavorably with polymer (clouding polymer) or surface (hydrophobic surface)

Solvency effects

Deposition/adsorption depends on an interplay between different interactions

The poorer the solvent the better the adsorption

���Solvency depends on: ���

polymer polarity���molecular weight���

complexation ���temperature

The influence of the solvent

Development of modern shampoo

the best way to keep damage to a minimum is to condition regularly and thoroughly. This helps to keep the cuticle intact, lower friction and reduce static charge on the hair

shampoos are simplicity out of complexity

What is in a shampoo? Cleansing agents: surfactants: anionic, amphoteric, nonionic Conditioning agents: silicone oils, cationic polymers Functional additives: thickeners, pH controllers Preservatives: sodium benzoate, parabens, EDTA etc. Aesthetic additives: colors, perfumes, pearlescing agents Medically active ingredients: zinc pyrithione, panthenol

www.pg.com

MIXTURES OF OPPOSITELY CHARGED POLYELECTROLYTE + SURFACTANT:

ASSOCIATIVE PHASE SEPARATION

How to eliminate/reduce phase separation?

•  1. Electrolyte

•  2. High concentration

•  3. Hydrophobic modification of polymer

•  4. Excess of one component (surfactant)

Implications for stability of formulations and deposition

H2O

P+S- solution

P+

S-

S-

+

Polymer-surfactant applications: implications for haircare of solvency

H2O

P+S- precipitate

S-

H2O P+

• A conventional polyelectrolyte-surfactant mixture in water is a four-component system • A full description requires a 3D phase diagram

polyelectrolyte

surfactant complex salt

simple salt

water

x

.

.

Full phase behaviour complex

K. Thalberg et al. J. Phys. Chem. 95 (1991) 6004

OPPOSITELY CHARGED MIXTURES: TWO ALTERNATIVE REPRESENTATIONS

conventional mixing plane alternative mixing plane

Stoichiometric mixtures belong to both mixing planes

Salt conc a hidden variable

Deposition of polyion-surfactant complexes by dilution: A one-step procedure

dilution

•  Start with re-dissolved soluble complex (excess surfactant) •  Dilute (rinse with water) => surfactant leaves the complex •  An insoluble complex separates out => one-step depositon

Used extensively in personal care, fabric care to deposit polyion-surfactant complexes & co-deposit various

“benefit agents” (often colloidal particles)

Phase separation, surface deposition and "redissolution" of complexes of polymer and surfactant carrying opposite charge

In situ monitoring of deposition by ellipsometry confirms phase diagram approach

Rinsing of adsorbed polymer/SDS layers on silica

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1000 2000 3000 4000 5000

time [sec]

adso

rbed

am

ount

[mg/

m2 ]

0.0

0.20.4

0.6

0.81.0

1.2

1.41.6

1.8

0.001 0.01 0.1 1 10SDS [mM]

adso

rbed

am

ount

[m

g/m

2 ] 2ƒÓ

Reference Adsorption of JR-400/SDS complexes from pre-mixed solutions

Rinsing was started (t=1000)

Rinsing was started after adsorption of the complex from pre-mixed solution reached steady state

- Deposition on rinsing: For the complexes which were formed in post-precipitation region, the adsorbed amount jumped up on rinsing

Effect of rinsing (10mM NaCl) on adsorption

5mM SDS 10mM SDS

0.06mM SDS 0.006mM SDS

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 1000 2000 3000 4000 5000 6000

Time [sec.]

Ads

orbe

d am

ount

[mg/

m2]

Effect of salt on rinsing on adsorbed polymer/SDS layers

on hydrophobized silica

a

b

c

The complexes adsorbed from mixed polymer (100 ppm)/surfactant (5 mM) solutions and rinsing was started at t = 1000 sec

(a)   adsorption was carried out in water followed by rinsing with water (b)  adsorption was carried out in 10 mM NaCl followed by rinsing with water (c)   adsorption was carried out in 10 mM NaCl followed by rinsing with 10 mM NaCl

Less deposition with salt

Rinsing of adsorbed HMP+/SDS layers on silica

Method:

Polymer JR-400 (100ppm) and SDS premixed solution was injected

After adsorption reached plateau, rinsing with 10mM NaCl was started (t=1000)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 1000 2000 3000 4000

time [sec]

adso

rbed

am

ount

[mg/

m2 ]

0

1

2

3

4

5

6

0.001 0.01 0.1 1 10

SDS [mM]

adso

rbed

am

ount

[mg/

m2 ] 2!

Effect of rinsing (10mM NaCl) on adsorption Reference

Adsorption of HMP/SDS complexes from pre-mixed solutions

Rinsing was started (t=1000)

Only weak additional adsorption of LM-200/SDS complexes in the post-precipitation region as opposed to JR-400/SDS complexes

Rinsing was started after adsorption of the complex from pre-mixed solution reached steady state

5mM SDS 10mM SDS

0.06mM SDS 0.006mM SDS

Lower depostion with hydrophobically modifed polymer: Higher solubility of LM-200/SDS complex. See phase diagram

COACERVATION in

HMPE + OPPOSITELY CHARGED SURFACTANT

PATH DEPENDENCE OF ADSORPTION

0

1

2

3

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8

Time, h

adso

rbed

am

ount

!, m

g·m

-2

adsorbed layer thickness, Å

1 mM NaCl

1 mM NaCl100 mM NaCl

0

1

2

3

0

50

100

150

200

250

300

0 1 2 3 4 5 6

Time, h

100 mM NaCl100 mM NaCl1mM NaCl H

2O

adso

rbed

am

ount

!, m

g·m

-2 adsorbed layer thickness, Å

Polyelectrolyte alone, cyclic changes in salt concentration

•  no relaxation of the adsorbed layer when ionic strength decreases •  once polymer (40DT) adsorbs, it never deattaches the surface

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

CO-ADSORPTION OF DT AND SDS

Adsorption from premixed solutions. Path dependence of co-adsorption of 80DT (50 ppm) and SDS (0.1 mM) versus variation in salt concentration

0

1

2

3

4

0

500

1000

1500

2000

0 2 4 6 8 10 12

Time, h

adso

rbed

am

ount

!, m

g·m

-2adsorbed layer thickness, Å

1 mM NaCl100 mM NaCl

1 mM NaCl

rinsingI II III

after rinsing, the amount of DT left on the surface is much higher than upon direct route of adsorption, without SDS

(rinsing removes surfactant)

0

1

2

3

4

0

500

1000

1500

2000

0 2 4 6 8 10

Time, h

adso

rbed

am

ount

!, m

g·m

-2adsorbed layer thickness, Å

100 mM NaCl

1 mM NaCl

100 mM NaClrinsing

I II III

•  Highly irreversible behaviour •  Possibility to tune the adsorption of

polyamphiphiles by the transient exposure to surfactants?

after rinsing, the amount of 80 DT left on the surface is much lower than upon direct route of adsorption, without SDS

Polyelectrolyte nanocapsules through LbL (Layer-by-Layer)

deposition on vesicular templates

Polyelectrolyte assembly on colloidal particles

Core-shell particles Hollow capsules

The versatility of LbL has allowed a broad range of material to be assembled on various substrates. The resulting multilayer properties such as composition, thickness and permeability depend on the type of species adsorbed, the number of layers and the conditions of the assembly process.

Targets: ������

hollow capsule production by means of a different and mild protocol. production of hollow capsules with dimensions in the submicrometer scale.

Matherials: Template and Polymers

Alginate and Chitosan

LbL assembly on vesicles: core-shell nanoparticles

Surface charge Size and Shape

Making hollow nanocapsules

Vesicle-to-micelle transition

Cuomo, F., Lopez, F., Miguel M.G., Lindman, B., Vesicle-templated Layer by Layer assembly for the production of nanocapsules, Langmuir 2010, vol. 26; p.10555-10560.

Making hollow nanocapsules

size distributions before and after the addition of tX, and after the dialysis. SEM observations prove the capsule

integrity after the dialysis.

Message

•  Counterion control (higher valency different) •  Electrolyte decreases counterion entropy •  Balance between electrostatics and hydrophobic

interactions •  Solvency effects