Ionic polysaccharides, solubility, interactions with surfactants, particle formation, and deposition

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 ΔS mix 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) Entanglements Extension Na Cl

Spherical Surfactant Micelle

Counterion entropy - - - - - - - - - - - Counterions - - - C SURFACE >> C BULK ΔS < 0 - - - - - - - - Unfavorable ΔG > 0 High CMC 60-80% Counterion Binding 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 Entropic gain of counterions Add salt Adsorption decreases

Case II: Polymer and surface have the same charge - - - - - - - - - - - - - - - - - - - - - - Entropic loss of counterions Add salt - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Adsorption increases

Deposition/adsorption depends on an interplay between different interactions Solvent Polymer Surface Aqueous systems: Adsorption occurs since water interacts unfavorably with polymer (clouding polymer) or surface (hydrophobic surface) Solvency effects

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

Polymer-Surfactant Interaction Cooperativity Surfactant micellization induced by polymer

When do surfactants bind to polymers? Ionic Surfactants Oppositely charged polymers Non-ionic polymers self-assembly induced by polymer All Surfactants Hydrophobically modified polymers mixed micellization Hydrophobic association is always essential to the interaction

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

Separation of the different contributions to the pressure polymer network polymer network hard spheres hard spheres

Separation of the different contributions to the pressure polymer network hard spheres Polymer network hard spheres charges charges

Separation of the different contributions to the pressure polymer network polymer network hard spheres Polymer network hard spheres charges hard spheres charges

Result P/!k B T 2.0 1.5 1.0 polymer network hard spheres Polymer network hard spheres charges 0.50 0.0 0.0001 0.001 0.01 0.1 "/2 network packing fraction polymer network

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 Make gel pieces of cross-linked polymer Immerse gel pieces in series of solutions with increasing conc of additive water water additive water more additive => Potential responsive gels (drug delivery, water retention ) => Info on interactions between gel & additive

Polymers Used in Gels Commercial cellulose derivatives cross-linked by divinylsulfone HEC (hydroxyethyl cellulose) HMHEC cat-hec ( JR400 ) C H 3 Cl ( C H N R cat-hmhec ( LM200 ) C H 2 2 O ) 2 C H 2 C H C H 2 O O H C H 3 C H 2 O H O O H H O O H O O C H 2 O C H 2 C H 2 O H 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 35 30 25 V/V 0 20 15 10 5 0.1 1 10 100 0 cac C f,sds

Gel Swelling Experiments Detect Surfactant Binding V / m (ml/g) 200 150 100 50 CMC: SHS STS SDS SDeS SOS HEC gels swollen in alkyl sulfate solutions Sjöström & Piculell Langmuir 17(2001)3836 => HEC binds alkyl sulfates with > 8 carbon tails 0 0 0.1 1 10 100 c (mm)

Cat-HEC Gels Different Anionic Surfactants V / m (ml/g) 1000 100 CMC: STS SDS SD(EO) 2 S Sjöström & Piculell Colloids Surf A 183-185 (2001) 429" Collapse & redissolution Two CAC:s!? 10 0 0.0001 0.001 0.01 0.1 1 10 c (mm) 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

Generic phase diagram for oppositely charged mixtures Association Thalberg et al. Anionic polysaccharide Cationic surfactant Nature of conc phase: conc soln/gel, liq crystal, solid crystal

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

Effect of salt on polyelectrolyte ionic surfactant Low salt Association Intermediate salt Miscibility High salt Segregation Thalberg et al.

Phase separation and redissolution by adding SDS to dilute solution of cat-hec H OR' H O R'O H H OR' H 0.1 100ppm UCARE LR-30M cac cac2 1:1 R'O H H OR' H O H O R O H R=H or R'=H or O n (CH 2 CH 2 O)n-CH 2 CHOHCH 2 N(CH 3 ) 3 Cl- (CH 2 CH 2 O)n-OH 2φ Absorbance at λ = 500 nm 0.08 0.06 0.04 0.02 1φ 1φ First increase in turbidity due to phase separation above CAC Then onset of redissolution at free surfactant concentration < CMC 0 0.001 0.01 0.1 1 10 100 SDS concentration SDS (mm) (mm) A.V. Svensson, L. Huang, E.S. Johnson, T. Nylander, L. Piculell, Appl. Mat. & Int. 1 (2009) 2431

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 shampoos are simplicity out of complexity What is in a 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 www.pg.com 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

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

Polymer-surfactant applications: implications for haircare of solvency S - P S - solution H 2 O H 2 O P P S - precipitate H 2 O P S - S -

Full phase behaviour complex A conventional polyelectrolyte-surfactant mixture in water is a four-component system A full description requires a 3D phase diagram K. Thalberg et al. J. Phys. Chem. 95 (1991) 6004 water. x. polyelectrolyte simple salt complex salt surfactant

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 1.4 1.2 Effect of rinsing (10mM NaCl) on adsorption Rinsing was started (t=1000) Reference Adsorption of JR-400/SDS complexes from pre-mixed solutions adsorbed amount [mg/m 2 ] 1.0 0.8 0.6 0.4 0.2 0.0 mm SDS mm SDS mm SDS mm SDS 0 1000 2000 3000 4000 5000 2 adsorbed amount [mg/m ] 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.001 0.01 0.1 1 10 SDS [mm] 2ƒÓ Rinsing was started after adsorption of the complex from pre-mixed solution reached steady state time [sec] Deposition on rinsing: For the complexes which were formed in post-precipitation region, the adsorbed amount jumped up on rinsing

Effect of salt on rinsing on adsorbed polymer/sds layers on hydrophobized silica 4.0 3.5 Adsorbed amount [mg/m2] 3.0 2.5 2.0 1.5 1.0 0.5 a b c Less deposition with salt 0.0 0 1000 2000 3000 4000 5000 6000 Time [sec.] 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

Rinsing of adsorbed HMP /SDS layers on silica 3.5 Method: 3.0 Polymer JR-400 (100ppm) and SDS 2.5 premixed solution was injected adsorbed amount [mg/m 2 ] Effect of rinsing (10mM NaCl) on adsorption mm SDS 2.0 After adsorption reached plateau, 1.5 rinsing with 10mM Rinsing was started (t=1000) NaCl was started (t=1000) 1.0 mm SDS 0.5 mm SDS mm SDS 0.0 0 1000 2000 3000 4000 time [sec] adsorbed amount [mg/m 2 ] 6 5 4 3 2 1 Reference Adsorption of HMP/SDS complexes from pre-mixed solutions 0 0.001 0.01 0.1 1 10 SDS [mm] Rinsing was started after adsorption of the complex from pre-mixed solution reached steady state 2! Only weak additional adsorption of LM-200/SDS complexes in the postprecipitation region as opposed to JR-400/SDS complexes Lower depostion with hydrophobically modifed polymer: Higher solubility of LM-200/SDS complex. See phase diagram

COACERVATION in HMPE OPPOSITELY CHARGED SURFACTANT

3 300 3 300 adsorbed amount!, mg m -2 2 1 1 mm NaCl 100 mm NaCl 1 mm NaCl 250 200 150 100 50 adsorbed amount!, mg m -2 adsorbed layer thickness, Å 2 1 100 mm NaCl 1mM NaCl 100 mm NaCl H 2 O 250 200 150 100 50 adsorbed layer thickness, Å 0 0 1 2 3 4 5 6 7 8 Time, h 0 0 0 1 2 3 4 5 6 Time, h 0 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 adsorbed amount!, mg m -2 4 3 2 1 I II III 100 mm NaCl 1 mm NaCl 1 mm NaCl rinsing 2000 1500 1000 500 adsorbed layer thickness, Å 0 0 0 2 4 6 8 10 12 Time, h after rinsing, the amount of DT left on the surface is much higher than upon direct route of adsorption, without SDS (rinsing removes surfactant)

4 I II III 2000 adsorbed amount!, mg m -2 3 2 1 100 mm NaCl 1 mm NaCl 100 mm NaCl rinsing 1500 1000 500 adsorbed layer thickness, Å 0 0 2 4 6 8 10 Time, h 0 after rinsing, the amount of 80 DT left on the surface is much lower than upon direct route of adsorption, without SDS Highly irreversible behaviour Possibility to tune the adsorption of polyamphiphiles by the transient exposure to surfactants?

Polyelectrolyte nanocapsules through LbL (Layer-by-Layer) deposition on vesicular templates

Polyelectrolyte assembly on colloidal particles 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. Hollow capsules Core-shell particles

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