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Introduction to Polymers

Introduction to Polymers. Kausar Ahmad Kulliyyah of Pharmacy, IIUM http://staff.iiu.edu.my/akausar. Contents. Polymers in drug delivery. Polymers in delivery systems: Examples. BLOCK COPOLYMERS. Consisting of block of two or more polymers

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Introduction to Polymers

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  1. Introduction to Polymers Kausar Ahmad Kulliyyah of Pharmacy, IIUM http://staff.iiu.edu.my/akausar Physical Pharmacy 2

  2. Contents Physical Pharmacy 2

  3. Polymers in drug delivery Physical Pharmacy 2

  4. Polymers in delivery systems:Examples Physical Pharmacy 2

  5. BLOCK COPOLYMERS • Consisting of block of two or more polymers • Example is poly(ethylene oxide)-poly(propylene oxide) block copolymers: H-OCH2CH2)a(OCH2CHCH3)b(OCH2CH2)cOH Physical Pharmacy 2

  6. ADVANTAGE OF BLOCK COPOLYMERS • degradation rate of polymers can be controlled. • can obtain controlled drug release • protect compound from harsh environment • e.g. in stomach – in particular polymers containing poly(lactic) acid or poly(glycolic) acid Physical Pharmacy 2

  7. EXAMPLE OF BLOCK COPOLYMERS Poly(lactic) acid Poly(glycolic) acid Physical Pharmacy 2

  8. POLYSACCHARIDES • Mainly due to formation of gels in aqueous solutions • Examples: • carrageenans • alginates • starch Physical Pharmacy 2

  9. Chemical Structure of Some Polysaccharides Used in Drug Delivery Physical Pharmacy 2

  10. Properties of Polymers • High molecular weight • Repeating units • Exist as linear or branched • Can be crosslinked • Properties depend on the polymerisation of the monomers • Can be divided into homopolymers or copolymers Physical Pharmacy 2

  11. TYPES OF Copolymers These can be further divided into: • Alternating • Block • Graft or branched Physical Pharmacy 2

  12. Natural Polymers • Chemical modification can be carried out to change the properties • Example: Crosslinking Physical Pharmacy 2

  13. Rigidity Physical Pharmacy 2

  14. Structure of polymer Physical Pharmacy 2

  15. Crosslink Density Physical Pharmacy 2

  16. MOLECULAR WEIGHT/TEMPERATURE & POLYMER PROPERTIES From: Florence & Attwood Physical Pharmacy 2

  17. Molecular Weight Physical Pharmacy 2

  18. Molecular Weight Determination Methods that can be used are:- • Chemical analysis • Osmotic pressure • Light scattering measurement • Gel permeation chromatography Physical Pharmacy 2

  19. Average MW • The averages can be in terms of:- • Number • Weight • Viscosity • Z (sedimentation) • The above depends on the type of analytical method employed Physical Pharmacy 2

  20. Determined by: Osmometry End-group titration Colligative properties Number Average MW Physical Pharmacy 2

  21. Determined from Light scattering Small Angle Neutron Scattering (SANS) Sedimentation velocity [Hiementz] Bias towards larger molecules Weight Average MW Physical Pharmacy 2

  22. Viscosity Average MW Determined by intrinsic viscosity Physical Pharmacy 2

  23. Mark-Houwink Equation h = KMva • ‘K’ and ‘a’ are the Mark-Houwink parameters and depend on polymer-solvent characteristics. • rigid rods, a=2. • hard sphere, a=0. • good solvent, a=0.8 Physical Pharmacy 2

  24. Z-Average MW Determined by sedimentation equilibrium Physical Pharmacy 2

  25. Polydispersity • The ratio of Mw/Mn is the degree of polydispersity Mw/Mn> 1 • The smaller the ratio, the narrower is the distribution in molecular weight of the polymer Physical Pharmacy 2

  26. MOLECULAR WEIGHT DISTRIBUTION Physical Pharmacy 2

  27. References Aulton, M. E. (1988). Pharmaceutics: The Science of dosage form design. London: Churchill Livingstone. Wise, D. L. (2000). Handbook of Pharmaceutical Controlled Release Technology. New York: Marcel Dekker. Chasin, M & Langer, R (1990). Biodegradable polymers as drug delivery systems. New York: Marcel Dekker. Vyas, S. P & Khar, R. K. (2002). Targeted and controlled drug delivery. New Delhi: CBS. Physical Pharmacy 2

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