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Polymer Solutions

Polymer Solutions. Kausar Ahmad Kulliyyah of Pharmacy, IIUM http://staff.iiu.edu.my/akausar. Contents. Molecular characteristics Polymer assemblies Polymer dissolution Polymer swelling Viscosity of polymer solutions Solubility factors Gel Interactions in polymer solutions

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Polymer Solutions

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  1. Polymer Solutions Kausar Ahmad Kulliyyah of Pharmacy, IIUM http://staff.iiu.edu.my/akausar Physical Pharmacy 2

  2. Contents • Molecular characteristics • Polymer assemblies • Polymer dissolution • Polymer swelling • Viscosity of polymer solutions • Solubility factors • Gel • Interactions in polymer solutions • Solubility parameter Physical Pharmacy 2

  3. Molecular Characteristics • Polymers are dispersed as isolated molecules in very dilute solutions • molecular characteristics necessary for understanding polymer properties can be determined: • chain length, conformation, and flexibility http://www.chem.sci.osaka-u.ac.jp/graduate/mms/English_version/Norisuye_lab.html Physical Pharmacy 2

  4. xanthanT. Sato et al. Macromolecules, 17, 2696 (1984) • A polyelectrolyte polysaccharide which is produced by a parasitic bacteria on cabbage and used as a food gum. This polymer takes double-stranded helix structure in aqueous solutions with salts. Physical Pharmacy 2

  5. Polymer Assemblies In solution, polymer chains exist in various states e.g. • uniformly molecularly dispersed state (dilute) • aggregating or micellar state • a number of polymer chains are assembled together • gel state • polymer chains form a network though the system • liquid crystalline state • polymer chains align toward a certain direction Physical Pharmacy 2

  6. Factors affecting polymer assemblies • chemical structure • chain conformation • intermolecular interaction of polymers Physical Pharmacy 2

  7. InterpolymerInteraction Physical Pharmacy 2

  8. Concentrated solution Physical Pharmacy 2

  9. Liquid crystal Physical Pharmacy 2

  10. Helix Physical Pharmacy 2

  11. Association micelle, gel Physical Pharmacy 2

  12. Amphiphilic Polymers Physical Pharmacy 2

  13. Polymer Dissolutionhttp://www.psrc.usm.edu/macrog/property/solpol/ps1.htm • the dissolution of a polymer is a slow process • due to size, structure/coiled shape, MW & the attraction forces between them, polymer molecules become dissolved quite slowly than low molecular weight molecules. • when a low MW solute such as sucrose is added to water, the dissolution process takes place almost immediately. • The sugar molecules leave the crystal lattice progressively, disperse in water, and form a solution. Physical Pharmacy 2

  14. Polymer Dissolution Process • Billmeyer Jr. (1975) points out that there are two stages involved in this process: • polymer swelling • dissolution Physical Pharmacy 2

  15. Polymer swelling Physical Pharmacy 2

  16. dissolution process for polymer molecules Physical Pharmacy 2

  17. Viscosity of polymer solutions Physical Pharmacy 2

  18. Solubility Factors Physical Pharmacy 2

  19. Gel Physical Pharmacy 2

  20. Type 1 Gel Physical Pharmacy 2

  21. Type 2 Gel Physical Pharmacy 2

  22. Heterogels • A copolymer A-B may exhibit different structure • when immersed in different solvents • depending of the swellability of the composites A and B towards the solvent Physical Pharmacy 2

  23. Interactions in Polymer Solutions Physical Pharmacy 2

  24. Interaction with solvents • Swelling and drug release: Sw = vd(t)/D Sw - swelling interface number v - the viscosity of solvent, d(t) - thickness of polymer D - diffusion coefficient of drug in polymer • Swelling is a function of temperature • Application in disposable towels and nappies Physical Pharmacy 2

  25. Solubility Parameter • unit (cal/cm3)1/2or SI unit: (cal/cm3)1/2 = (4.187 J/10-6m3)1/2 = 2.046 x 103 (J/m3)1/2 = 2.046 MPa1/2 • solubility parameters useful when studying how capable is a polymer to being dissolved in a given solvent. • above equation is valid only for solutions where strong polymer-solvent interactions do not take place. Physical Pharmacy 2

  26. Solubility parameters for solvents & Polymers From "Polymer Handbook" / J. Brandrup and E.H. Immergut, Eds., 3rd Ed., Wiley-Interscience, New York, 1989) Physical Pharmacy 2

  27. References Aulton, M. E. (1988). Pharmaceutics: The Science of dosage form design. London: Churchill Livingstone. Chasin, M & Langer, R (1990). Biodegradable polymers as drug delivery systems. New York: Marcel Dekker. Florence, A. T. & Attwood, D. (1988). Physicochemical Principles of Pharmacy (2nd ed.). London: Chapman & Hall Martin, A. N. (1993). Physical Pharmacy: Physical chemistry principles in Pharmaceutical Science (4th ed.). Philadelphia: Lea & Febiger. Vyas, S. P & Khar, R. K. (2002). Targeted and controlled drug delivery. New Delhi: CBS. Wise, D. L. (2000). Handbook of Pharmaceutical Controlled Release Technology. New York: Marcel Dekker. Physical Pharmacy 2

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