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โดย รองศาสตราจารย ์เรอืงศร ีวฒัเนสก์

ruangsri@gmail.com

CHEM 324 : Physical Chemistry IV Part II Department of Chemistry, Faculty of Science, CMU. August 2009

Introduction toColloid & Surface

Chemistry

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Contentö The Colloidal State :

Classification & preparation Surfactant & micellization

ö The Properties of Colloidal Dispersion (Size & shape determination) :

Colligative propertiesKinetic properties

Optical propertyö Colloidal Stability and Its Applications

The electrical double layer ö - - The gas liquid and liquid liquid interfacesö The adsorption of gas on the solid surfaceö - The liquid solid interface

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References1 . Atkins, P. W., Physical Chemistry, 8th ed., Oxford Univers

ity Press, Oxford, 2006.2. Hiemenz, P. C. and Rajagopalan, R ., Principles of Colloid C

hemistry and Surface Chemistry : Revised and Expanded , 3rd ed., Marcel Dekker, New York, 1997.

3. Hiemenz, P. C., Principles of Colloid Chemistry and Surfa ce Chemistry, Marcel Dekker, New York, 1977.

4. Hunter, R, J., Introduction to Modern Colloid Science, Oxfo rd University Press, Oxford, 1998.

5. Shaw, D. J., Colloid &Surface Chemistry ,4th ed., Butterwo rth, Oxford, 1998.

6. http://wikipedia.com and other websites

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Evaluation

• Assignment/Homework/Quiz 20 points• Report/Presentation 20 points• Final Exam 60 points

Total 100 points (50%)

(Final exam : Sept 24, 2009 : 12-15 pm.)

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1. The Colloidal State

Definition : particle with linear dimension between

10-7 cm (10 AO) and 10-4 cm (1 )1 - 1000 nm

Other definitionsparticle weight/ particle size etc.

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Length ScalesC-C bond 0.1 nmRadius of Gyration 1 nmMicelles 10 nmVesiclesEmulsion Droplets 100 nmLatex Particles“Colloidal Crystals” 1000 nm

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H omogeneous M ixtures(T rue composition and properties)

Property True solution Colloid Suspension

Particle type Ions, small molecules

Large molecules, particles Large particles

Particle size 0.1-1 nm 1-100 nm 100 nm and larger

Tyndall effect No Yes Yes

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CColloidal olloidal SSystemsystemsDispersed Medium

Gas Liquid Solid

Cont. Mediu

m

Gas NONE Liquid Aerosol Liquid Aerosol FogFog, mist

Solid Aerosol Solid Aerosol SmokeSmoke, air particulates

Liquid

Foam Foam Whipped cream

Emulsion Emulsion MilkMilk, mayonnaise,

hand cream

Sol Sol Paint,

pigmented ink, blood

SolidSolid FoamSolid Foam

Aerogel, styrofoam,

pumice

Gel Gel Gelatin, jelly, cheese, opal

Solid SolSolid Sol Cranberry glass,

ruby glass

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aerosols, emulsions, sol,foam, paste

CColloidal olloidal Dispersion Macromolecular Colloids

Silica gelZeolite

Basalt

Associated Colloids

Micelle formationSurfactants

“surface active agents”

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CMC determinations

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Common Surfactant Classes

Br_

N+

cetyltrimethylammonium bromide (CTAB)

sodium dodecylsulphate (SDS)

O S OO

O

_Na+

polyethylene oxides (CiEj )

O O O OH

Cationic

Anionic

Non-ionic

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C12E6 adsorbed at theair-water interface in the presence of oil

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Biocolloids

myoglobinhaemoglobin

Megaspore wall from a fossil of Salvinia cerebrata.

Nano “golf balls”

Multiple Colloids

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PPreparation of reparation of CColloidal olloidal SSystemsystems Two basic methods of forming a colloid :reduction of larger particles to colloidal size condensation of smaller particles into colloidal particles i.e.

• spontaneous dispersion in the proper solvent• metal evaporation in an electric arc to form a metal vapor cools.

• solid reduction in a colloid mill .• emulsion preparation by homogenization with the addition of an emulsifying agent.

• Condensation of smaller particles to form a colloid usually involves chemical reactions—typically displacement, hydrolysis, or oxidation and reduction

•making colloidal gold, colloidal silver .

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Some areas of Science and Technology in which particles in the colloidal size range are regularly encountered

Analytical chemistry :adsorption indicators, ion exchange, nephelometry, precipitate filterability, chromatography, and decolorization

Physical chemistry :nucleation; superheating, supercooling and supersaturation; and liquid crystalsBiochemistry and molecular biology :electrophoresis; osmotic and Donnan equilibria and other membrane phenomena; viruses, nucleic acids, and proteins; and hematology

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Chemical manufacturing :catalysis, soaps and detergent, paints, adhesives, ink; paper and paper coating; pigment; thickening agents; lubricants

Environmental science :aerosols, fog and smog, foams, water purification and sewage treatment; cloud seeding; clean rooms

Materials science :powder metallurgy, alloys, ceramics, cement, fibers, and particles of all sorts

Petroleum science, geology and soil science :oil retrieval, emulsification, soil porosity, floatation, and ore enrichment

Household and consumer products :milk and dairy products, beer, water proofing, cosmetics, and encapsulated products

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Assignment -1

1. Search from Journals or websites to find an example, in any branches of Science,of which particles in the colloidal-size range are encountered.

2. Write up in your own words a concise report in A4 paper.3. Report is due on August 21, 2009. (10 points)