Introduction SM

Shlomo Magdassi

Casali 204

[email protected]

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INTERFACIAL

PHENOMENA and

MICRO-NANOPARTICLES

A. Interfacial phenomena and colloid chemistry

1. Basic concepts; surface energy; systems characterization.

2. Adsorption at interfaces.

3. Electrical charges at interfaces

4. Colloidal systems.

5. Wetting, foaming, detergency.

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PEPPER

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4

• Precipitation and chemical reduction in solutions.

• Evaporation from emulsion.• Reaction in a gas phase.• Grinding.• Polymerization in emulsion.• Syntheses in ordered systems • Sol-gel.• Reactions at the interface.• Coacervation.

B. Particles

6. Fundamental processes for theachievement of particles

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• Organic microspheres• Microcapsules• Metallic nanoparticles• Latex

7. Representative processes for preparation of particles;

Bibliography

1. Principles of Colloid and Surface Chemistry, P.C. Hiemenez, Marcel Dekker, N.Y., 1977.

2. Physical Chemistry of Surfaces, A. Adamson, John Wiley & Sons, N.Y., 1990.

3. Surfactants and Interfacial Phenomena, M.J. Rosen, 1991.

4. Specific references indicated during class.

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Additional books related to this course can be found in the library.

Key words: Interfaces, surfactants, colloid chemistry, adsorption, emulsions, dispersions, nanoparticles, microparticles, etc.

•Attending Classes

At the surface, attractive forces act asymmetrically.

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Change in general energy as a result of a change in surface area.

Surface layer

Water-Air Interface

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Interface Increased Energy

H2O

C18H38

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dG = dA

= ( )T,V,ndGdA

GS = Surface Free Energy, erg/cm2

GS minA min

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A change in general energy as a result of a change in surface area.

Curvature ofliquid surface

Coalescence ofof droplet

Formally, the surface tension is defined as the partial derivative of the free energy G with respect to area A.

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Division of bulk into particles:Increased Surface Area

1 cm3 , A = 6 cm2

1 µm3 cubes,

A = 6 104 cm2

0.1 µm3 cubes,

A = 6 105cm2

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Dispersion Systems: ExamplesDispersion Systems: Examples

Aerosols

Paints

Cement

Cosmetic Creams

Particle/Droplet Size

Surface Energy

Interactions/Stabilization

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Colloid = Glue (Greek) 14

Acceptable nameDispersion phaseMediumAerosolLGAerosolSGFoamGLEmulsionLLSuspension, colloidal solution

SL

Solid foamGSGel, solid emulsionLS

AlloySS

Two-Phase Colloidal Systems: Definitions

Dispersion Systems – ExamplesDispersion Systems – Examples

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ExamplesNameMediumDispersed phase

FogLiquid aerosolGLDustSolid aerosolGSSoap bubblesFoamLGMilk,cosmetic cream

EmulsionLL

Paint, inkSol, suspensionDispersion

LS

Tooth pastePasteInsulating foamSolid foamSGMargarineSolid emulsionSLDry paintSolid

dispersionSS

Micelles

Typical Colloidal Dispersions

Dispersions

Emulsions16

Virus Clay

Particles in Nature

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E Ink ( Kindel )

Surfactants

RCOO-Na+ R8-18c

log C

cmc

wettingmicellesemulsionflocculation

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SDS MicelleSDS Micelle

Micellar Solutions (Shampoo)

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Self Organized StructuresSelf Organized Structures

A) A cylindrical micelleA) A cylindrical micelle

B) A bilayerB) A bilayer21

Application of Colloid-Surface Application of Colloid-Surface PhenomenaPhenomena

Detergency

Enhanced oil recovery

Emulsification

Adhesion

Ore floatation

Lubrication

Water repellency

Protein adsorption

Latex formation

Precipitation

Filtration

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Colloid Chemistry in IsraelColloid Chemistry in Israel

Paints

Inks and printing

Resins

Cosmetics

Pharmaceutics

Agriculture

Food

Detergents

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d: edge of a cube

Cube: Total number of moleculesin a cube:

(molecule length = h) = d3/h3

Number of molecules at thesurface = 6d2/h2

Ratio of surface molecules:total number: 6h/d

Surface / bulk molecules

25

20

15

10

5

Perc

enta

ge o

f mol

ecul

es in

the

surf

ace

log d/m-2 -1 0 1 2

Variation of the percentage of molecules in the surface as a function of particle size for a substance with a molar volume of 30 cm3 mol-1

Percentage of moleculesPercentage of moleculesin the surfacein the surface

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air

liquid

Molecules will leave the interface for theinterior of the liquid.

Surface curvature

Surface Interface

Fluid Interfaces

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Surface TensionSurface Tension

C C’

D D’

dF

A

l

B

Surface area of a film (two sides) : l d 2 W = F d

If is defined as the force acting along DC (dyne/cm) F = l 2 W = l 2 d = S = W/S

is the work in ergs necessary to generate 1cm2 of a new surface

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The surface energy may be defined as the excess energy at the surface of a material

compared to the bulk. 29

In small dimensions, surface tension dominates over other forces

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Film: 0:30-2:05

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= Surface free energy per = Surface free energy per unit areaunit area

Dyne cm erg cm cm cm2 =

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Surface tensions of pure liquid(dynes/cm)

Water72.8Mercury485.0Nitrobenzene43.38Oleic acid32.5Benzene28.86Toluene28.4n-Octane21.77n-Hexane18.43Olive oil35.8Molten metals350-1800Ethanol22.5

Surface Tension - Solution

surfactants

NaCl/water

Water/ethanol

Isooctane/Benzene Molten Nitrates

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Surfactants

RCOO-Na+

Soap

R8-18c

log C

cmc


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OF SOLUTIONSChanges at High Concentrations

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Temperature EffectTemperature Effect

T

= o (1- T/TC)n

Guggenheim-Katayama

o - constant for each liquid n - empirical factor, ~1.3 organic liquidcritical temperature - TC

Pressure EffectPressure Effect

P

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Surface Tension of Water as a Function of Temperature

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BSA

40

50

2 6

t (hrs)

0.1 mg/ml

1 mg/ml

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72

5 15

t (msec)0.1N adipic acid

HOOC - (CH2)4 - COOH

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Dynamic Surface Tension

Water Calming Film

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demonstration - wetting with heating

12 Hexane 51.0 18.4

CCl4 48 26.9

Benzene 35 28.9

n-Octanol 8.5 27.5

n-Hexanol 6.8

n-Pentanol 4.4

n-Butanol 1.6

Ethanol

Mercury

?

375 485

מתח בין-פנים : נוזל/מים

WaterWater

Hexane Butanol

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1. Antonoff’s Rule 12 = 1 - 2

(1,2 at saturation)

2. Girifalco & Good

12 = 1 + 2 - 2(12)1/2

= 4V11/3 V2

1/3

(V1 1/3 + V2 1/3)2 V - molar vol.

Estimation of Interfacial Tension

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3. Owens & Wendt

Surface tension value is composed of polar (P) and non-polar (d) parts

12 = 1 + 2 - 21d 2

d - 21p 2

p

w =h + d = p + d

Estimation of Interfacial Tension

http://www.firsttenangstroms.com/pdfdocs/OwensWendtSurfaceEnergyCalculation.pdf

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oil (dwater oil)1/2

(dwater oil)1/2 water

Schematic representation of the contributions to an oil-water interfacial tension.

Oil phase

Water phase

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Data:

12 hexane water : 51.1 dyne/cm

hexane = 18.4 dyne/cm

H2O = 72.8 dyne/cm

phexane = 0

51.1 = 18.4 + 72.8 - 2wd 18.4

wd = 21.8 dyne/cm

wh = 72.8 - 21.8 =51 dyne/cm

Adhesion p,d

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An Example for Calculating d p

Surface CurvatureSurface Curvature

R

gas

G1 = 4R2, G2 = 4(R2 - 2Rdr + dr2)

G 8 Rdr

P 4R2dr = 8 Rdr Work against pressure difference.

P = 2 (/R) ( P = 4 (/R) for two surfaces )

Young & Laplace : P = (1/r1 +1/r2 )

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Sphere: r1 = r2

Flat surface: r1 = r2 =

Δp for water drops of different radii at

Droplet radius1 mm0.1 mm1 μm10 nm

Δp (atm)0.00140.01441.436143.6

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r

h

Capillary rise

Wetting

P=0

r

h

non-Wetting

Capillary depression

P = 2/r P = gh hydrostatic pressure

= (rhg )/2 ( = 0o, 180o)

Liquids in Capillaries

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Up to 200 lit/hr!

Filling channels, membranes

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= (rhg )/2

Chloroform: d = 1.476 g/cm3 h = 3.67 cm r = 0.01 cm = ?

= 0.50.013.671.476981 = 26.6 (g·cm/sec2·cm)

Water: = 72 dynes/cm h = 9.9 cm

Water, r = 0.1 cm h = 0.99 cm

Surface Tension Measurementby a Capillary

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= 26.6 dynes/cm

Capillary demo

Surface Tension Measurements Methods

R >> rf = 2·2R ( =0 ) = f/4 R

f

For i, ring must be wetted (=0 ) by the lowerLiquid. If CCL4/H2O, ring must be hydrophobic54

Ring Method (Du Nouy)

From:http://www.kruss.de/en/theory/measurements/surface-tension/ring-method.html 55

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Interfacial Tension ofClean and Dirty Engine Oils

Inte

rfac

ial T

ensi

c

Time(s)

Synth-CSynth-DNat-CNat-DSunOil

Wilhelmy Plate MethodWilhelmy Plate Method

Wtotal = Wplate + 2( w + t )

Wtotal = Wplate + 2( w + t ) ·cos

0 = 0

(for complete wetting (=0)

w : width t : thicknessW : weight

platinum, glass, mica

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C12 O S O- Na+

O

O

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Drop weight method (drop and tip enlarged)2r = mg

= (mg/ 2r)

mg: max. weight which can be supported by surface forces. : empirical tables.

Drop Weight MethodDrop Weight Method

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Pendant Drop Method

The shape of the drop is determined by its radii of curvature.

SE

Sw

H=S E

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* Maximum bubble pressure:

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P + P1 = gh +2/R

Contact Angle

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Wetting demo

Sessile DropSessile Drop

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Oscillating Jets

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Droplet Ejection Process HP Printer

• viewing

From : C. Shih, http://www.eng.fsu.edu

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Formation of Particles by Jetting

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Controlling Surface Tension by Surfactants

RCOO-Na+ R8-18c

log C

cmc


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O

1. Anionic

2. Cationic

3. Zwitterionic

4. Nonionic

R C OO() Na(+)

R (+)N(CH3)3 Cl()

R (+)NH2CHCH2 COO()

C OH

C O C R

C O C R’

O

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Surfactants Classification

•Module :Amphiphilic structure : 1-7

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Usage of Surface Active Agents

Micellization – solubilizationProduction and stabilization of emulsions

Production and stabilization of dispersionsFoaming

FluctulationFloatationWetting

Products: Detergents, medical and cosmeticemulsifiers, inks and paints.

Demo Foaming,

Wetting With Surfactant

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Film:

0-2:57

4:46-13:35

18:30-20:20

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Introduction SM

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