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Gels and Gelformation

Gels and Gelformation. Colloidal Gel Structures (Wolfgang Ostwald). Semisolids, consisting of at least two components: The first component, being in the solid state, builds up a coherent three-dimensional network -also called matrix, texture or constituent phase-

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Gels and Gelformation

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  1. Gels and Gelformation

  2. Colloidal Gel Structures(Wolfgang Ostwald) Semisolids, consisting of at least two components: The first component, being in the solid state, builds up a coherent three-dimensional network -also called matrix, texture or constituent phase- in which the second component (normally a solvent) is immobilized.

  3. Gels • Since both phases completely interpenetrate (bi-coherent system), a differentiation between the inner and outer phase cannot be made.

  4. Classification of Gels according to • Constituent or matrix phase • Solvent phase • Crosslinkage

  5. Classification of Gels

  6. Classification of Polymer Gels

  7. Classification of Gels

  8. Gel structures of creams  o/w creams  w/o creams  Amphiphilic creams

  9. Colloidal structures of o/w creams • Model system for cetostearyl creams: - Emulsifying Wax* 9,0% wt/wt - Liquid paraffins 10,5% wt/wt - White Petrolatum 10,5% wt/wt - Water 70,0% wt/wt *Emulsifying Wax itself consists of : Cetyl sulfate sodium 5% wt/wt Stearyl sulfate sodium 5% wt/wt Cetyl alcohol 45% wt/wt

  10. Colloidal structures of w/o creams • A general formula of a w/o system: - Lanolin* 3,0% wt/wt - Cetostearyl alcohol 0,25% wt/wt - White Petrolatum 46,75% wt/wt - Water 50,0% wt/wt * with cholesterol as the most important ingredient

  11. Colloidal structures of amphiphilic creams • Formulation of an amphiphilic „basic cream“: - Glyceryl stearate 4,0% wt/wt - Cetyl alcohol 6,0% wt/wt - medium chain triglycerides 7,5% wt/wt - White Petrolatum 25,5% wt/wt - PEG-20 glyceryl-stearate 7,0% wt/wt - Propyleneglycol 10,0% wt/wt - Water 50,0% wt/wt

  12. Colloidal structures of amphiphilic creams • Self-assembled structures • Do-it-yourself cosmetic formulations

  13. Polymer Gels • Polymer Gels are cross-linked networks swollen with a liquid  Gels have both liquid-like and solid-like properties

  14. Polymer Gels(The Language of Colloid and Interface Science) • A suspension or polymer solution that behaves as an elastic solid rather than a liquid.

  15. Typical rheological behaviour of gels: storage modulus (G`) > loss modulus (G``)

  16. How we can come to gels ?

  17. Chemical gelation(covalently crosslinked polymer networks) • Ion exchanging resins • Hydrogels, e.g. HEMA copolymers used for soft contact lenses • Superabsorptive resins

  18. Physical gelation(noncovalently crosslinked polymer networks) • Via hydrogen bonds • Via Coulombic bonds • Via hydrophobic bonds • Via Van der Waals bonds

  19. Three classes of gels • Molecularly connected • Phase connected (adhesive) • Phase connected (continuous)

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