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  • 1

    Colloid chemistry for pharmacy students

    The subject of colloid chemistry. Why are colloids so different?

    Classification, characterization of colloid systems.

    www.kolloid.unideb.hu

    1. lecture

    Zoltn Nagy, Bnyai Istvn lecturer professor

    Univ. of Debrecen, Dep. of Colloid- and

    Environmental Chemistry

  • Motivation 1

    Everyday experiences

    Silicosis (size), red mud (accident in Hungary), asbestos (shape)

    Smog

    New alloys (micro structure) (implants)

    Functional polymers (biological macromolecules, drug delivery)

    Nanotechnology

    Fluorescence is size dependent (diagnostic)

    TiO2 catalytic activity (cosmetics)

    Drug release rate

    Drug imbibition

    Wetting of solids

    Solubilization of drugs

    Polymorhism

  • 3

    Reading Barnes, GT, Gentle, IR: Interfacial Science ,

    Oxford UP. ISBN 0-19-927882-2, 2005

    Cosgrowe T.: Colloid science Blackwell Publishing ISBN:978-14051-2673-1, 2005

    Erbil, H. Y.: Surface Chemistry Blackwell, ISBN 1-4051-1968-3, 2006

    Atwood, D., Florence, AT: Phyisical Pharmacy Pharmaceutical Press 2008, ISBN 978 0 85369 725 1

    Pashley, R. M.: Applied Colloid & Surface

    Chemistry Wiley&Sons, ISBN 0-470-86883-X, 2004

  • 4

    Exam, requirements

    Written test one test in an exam period (2 possibilities )

    Slides: kolloid.unideb.hu

  • 5

    Place of colloid science

    1. partly physical chemistry Not (only) the chemical composition is important the states are independent of the composition

    2. partly physics the physical properties are important basic law of physics are used

    3. partly biology the biological matters are colloids the mechanisms of living systems surface chemistry (enzymes)

    biology

    chemistry

    physics

    organic

    chemistry

    physical chemistrybio-

    chemistry

    colloid science

  • Lectures

    1. Colloids. Physical chemistry basics. Colloid systems

    2. Molecular, interparticle interactions.

    3. Liquid-gas, solid-gas, solid-liquid interfaces

    4. Surface chemistry: L-G, S-G, S-L surfaces

    5. Adsorption at gas-solid interface

    6. Adsorption from solutions. Strong electrolytes

    7. Electric double layers

    8. Electrokinetic phenomena

    9. Colloid stability: lyophobic colloids 10. Foams, emulsions

    11. Macromolecules

    12. Association colloids

    13. Rheology and structure

    6

  • 7

    Subject of colloid chemistry: systems consist of particles in size of 1nm 500 nm.

    systems in which the surface plays a significant role

    m

    nm

    1010 810 610910 710 510 410 310

    0.1 1 10 210 310 410 510 610

    Atoms, small molecules

    macromolecules

    smoke

    kd

    colloid

    micelles virus pollen, bacterium

    microscopic heterogeneous

    Homogeneous Heterogeneous systems

    (macroscopic phases) colloid system

    Homogeneous

  • 8

    Homogeneous, heterogeneous ?

    Homogeneous: isotropic. (5% solution of NaCl or gelatine?) Heterogeneous systems, Gibbs phases rule

    interface

    Homogeneous one

    phase

    Heterogeneous more

    phase

    It is not distinguishable by appearance. Soup, jelly, milk, beer, bread, pudding-pie, fog, smoke, smog, soils, toothpaste, blood, mayonnaise, whip, opal, solution of soap, etc.

    Gold sol

    continuum? dotlike?

    2 CFP

    degree of dispersion

  • Colloids in everyday life

    9

    Colloids cannot be classified as homogeneous or heterogeneous system

    Aerogel, frozen smoke

    liogel tenzids

    Some times naturally visible, somtimes hidden.

    Xerogel, modern opal

    Homogeneous one

    phase

    Heterogeneous more

    phase

  • 10

    The colloidal state 1. Definition of colloid state

    history:

    Solution (Graham) and suspension theory,

    homogeneous-heterogeneous

    2. Ultramicroscope, dark field microscope

    R. Zsigmondy Nobel price: 1925

    "for his demonstration of the heterogenous nature of colloid solutions and for the methods he used, which have since become fundamental in modern colloid chemistry"

    http://www.wsu.edu/~omoto/papers/darkfield.html

  • 0.0

    0.2

    0.4

    0.6

    0.8

    1.0E-7 1.0E-6 1.0E-5 1.0E-4 1.0E-3 1.0E-2 1.0E-1 1.0E+0

    R ,cm

    surf

    ace m

    ole

    cule

    s/ to

    tal

    0.1 % 1 %

    the effect of surface can

    not be ignored

    10 %

    R

  • 12

    Sub-microscopic discontinuity

    d e n s ity d en sity

    x x

    Forming a disperse system by

    breaking of b phases (any kind

    of phases except from 2 gas)

    blocks:

    molecules

    particles

    W. Ostwald: the colloidal state is independent on the chemical forms

    Aladr Buzgh : submicroscopic discontinuities

    A: two homogeneous phases form a heterogeneous system

    D: two components form a homogeneous solution, particles are smaller than 1 nm

  • Motion in colloid solutions or dispersions

    1. Gravitational force: tending to settle or rise particles depending on the density

    2. Viscous drag force: arises as a resistance to motion, since the fluid has to be forced apart as the particle moves thorugh it.

    3. Natural kinetic energy of particles: Brownian motion

    13

  • Motion causes separation

    14

    36 4 ( ) / 3drag p liq gravF rV r g F

    r = radius (m); V = volume (m3); = viscosity (Pas);

    p and liq densities (kg/m3);

    g = gravitation acceleration (m/s2)

    = 1g cm-3

  • Brownian motion

    Each particle has a kinetic energy: appr. 1 kT

    15

    2 211 4 10 J2

    kinE mv kT

    This leads us to colloid science because small particles moves fast (no sedimentation) but a lot of collision: may cause aggregation because of the van der Waals interactions.

  • Messages

    1. In colloid state the heterogeneity and homogeneity have no meaning, or have different meaning.

    2. All materials can be in colloid state

    3. The colloid state is not defined in sharp terminology.

    Colloids are the systems:

    in which particles are between 1-500 nm in size (microscope).

    where the surface particles strongly affect the behaviour.

    in solution the Brownian motion is typical (energy is larger than that of the sedimentation)

    16

  • Classifications

    17

  • 18

    Coherent and incoherent systems

    Incoherent systems Fluid phase characters Particles moves individually (the cohesive forces

    (attraction) are weaker than the thermal energy) Coherent systems

    solid phase characters (cross-linking by covalent or interparticle forces) (the cohesive forces (attraction) is stronger than the thermal energy)

    network structure (the anisometry helps the formation of network )

    Intermediate systems (semisolids) creams, pastes, gels (rheology: tixotropy)

  • 19

    Type of colloids on the basis of structure (appearance)

    Porodin

    colloids

    Incoherent (fluid-like) Coherent (solid-like) gel

    Colloidal Dispersions sols

    Macromol. solutions

    Association Colloids

    Colloidal solutions

    (porous) Reticular Spongoid

    corpuscular fibrillar lamellar diszpersion macromolecular association

    liofb liofil liofil

    (IUPAC proposal)

    http://en.wikipedia.org/wiki/Image:SilicaGel.jpg

  • categorized by inner / outer phases

    20

    Type of sols (incoherent)

    aerosols liosols xerosols, xerogels

    L/G liquid in air: fog, mists, spray

    S/G solid aerosol, solid in gas: smoke, colloidal powder

    Complex, smog

    G/L gas phase in liquid (sparkling water, foam, whipped cream)

    L/L emulsion, liquid in liquid, milk

    S/L colloid suspension (gold sol, toothpaste, paint, ink)

    G/S solid foam: polystyrene foam

    L/S solid emulsion: opals, pearls

    S/S solid suspensions: pigmented plastics

    http://www.clarkson.edu/camp/reports/dec01/pictures/page3d.JPG

  • 21

    Macromolecules (incoherent) The probable shape and weight of some proteins

    Colloidal particles are much larger than the solvent molecules in a solution, the properties of these particles depend on their size and shape

    Illustration of a polypeptide macromolecule

  • 22

    Association colloids (incoherent)

    Surfactant (soap and detergent)

    spherical micelle (targeted medicine) amphiphilic

    Micelles are the simplest of all self-assembly structures

  • Coherent systems

    examples

    23

  • 24

    Gels (most interesting in coherent systems)

    Solid-like consistency

    Examples: gelatins, collagens (proteins), pectins (polysacharide) may be used for food as a stabilizer, thickener, or texturizer for such as ice cream, jams , yogurt, cream cheese, margarine; it is used, as well, in fat-reduced foods, to simulate the mouth feel of fat to create volume without adding calories. Pharmaceutical capsules in order to make their contents easier to swallow, microcapsule for photografic films , hair styling cream

    Blood, coagulated blood, milk sour cream

    http://en.wikipedia.org/wiki/Stabilizerhttp://en.wikipedia.org/wiki/Ice_cre

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