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1. 1 Hydrogels Prepared by: Roshan Saud

2. Contents Introduction Natural and synthetic hydrogels Classification Properties Applications 2

3. Introduction Hydrogels are cross linked polymers network that absorb substantial amount of aqueous solution. Hydrogels can contain over 10-95% water. Hydrogels are three-dimensional, hydrophilic, polymer network capable of imbibing large amounts of water or biological fluids. 3 Fig :Antibiotic Hydrogel for Wound Healing Protection

4. Introduction The networks are composed of Homopolymers or copolymers and are insoluble due to the presence of chemical crossings (Tie-points, junctions) or physical crosslinks such as entanglements or crystallites.  The hydrophilicity of the network is  due to the presence of hydrophilic groups such as -NH 2 , -COOH, -OH, -CONH 2 , - CONH -. 4

5. Natural hydrogels Examples of natural hydrogels include: protein-based hydrogels (e.g., gelatin, collagen)  polysaccharide-based hydrogels (e.g., starch, chitosan, alginate, and cellulose). fibrin, hyaluronic acid 5

6. Synthetic Hydrogels Synthetic hydrogels are interesting because it is easy to control their chemistry and structure and thus alter their properties. Examples of polymeric synthetic materials which can be used to form hydrogels are  poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and poly(propylene fumarate) (PPF) 6

7. Swollen hydrogel Dry solid 7

8. Classification Method of synthesis base 1) Homopolymer hydrogels 2) Co-polymer hydrogels 3) Multipolymer hydrogels Structure base 1) Amorphous hydrogels 2) Semi crystalline hydrogels 3) Hydrogen bonded hydrogels 8

9. Classification of hydrogels Homopolymers Contain only one type of monomer in their structure, and based on the nature of the monomer and techniques used for polymerization. Homopolymers may have cross-linked skeletal structure. Polyetheleneglycol (PEG) based hydrogels  9

10. Classification of hydrogels Copolymers Are composed of two or more types of monomers. At least one is hydrophilic in nature. MAA Methacrylic acid PEGME PEGMA poly(ethylene glycol) methyl ether poly(ethylene glycol) dimethyl acrylate 10

11. Classification of hydrogels Multipolymer interpenetrating Polymeric hydrogels (IPN) Linear polymer penetrate into another cross-linked network without any chemical bonding. Made of two independent cross linked synthetic or natural polymer components, in network form. Hydrogel formation by cross-linking of star-PEG and heparin. 11

12. Classification of hydrogels Non ionic hydrogels Neutral e.g. polymers of acryloymorpholine, N,N-dimethylacrylamide and N-vinyl pyrrolidone Ionic hydrogels Including anionic or cationic e.g. polymers acrylic acid-bis-(3-sulfopropyl-ester, potassium salt 12

13. Classification of hydrogels Amphoteric hydrogel Electrolyte containing both acid and base groups. Zwitterionic hydrogels Contain both Anionic and cationic groups in each structural repeating units. Example: sulfobetainemethacrylate. 13

14. Classification of hydrogels Amorphous hydrogels are glycerin- and water-based products primarily manufactured for the purpose of wound hydration. These dressings help maintain a moist wound healing environment. 14

15. Classification of hydrogels Semi crystalline hydrogels F irst developed in 1994. They are moderately water-swollen hydrogels containing crystalline domains. 15

16. Classification of hydrogels Hydrogen bonded hydrogels Hydrogel base on hydrogen bonds can be transparent . They are either soft and tough or strong and brittle. 16

17. Properties The highest absorption capacity (maximum equilibrium swelling) The lowest price. The highest durability and stability in the swelling environment and during the storage. The highest biodegradability without formation of toxic species following the degradation. Re-wetting capability (if required) the hydrogel has to be able to give back the imbibed solution or to maintain it. 17

18. Properties of hydrogels Properties of Hydrogels Swelling properties influenced by changes in the environment as temperature, solvent composition, pressure. Can be biodegradable and bioabsorbable. 18

19. Applications of hydrogels Hydrogels are used for producing contact lenses. H ygiene products and wound dressings. Other commercial uses of hydrogels are in drug delivery. The main advantage of hydrogel is that they possess a degree of flexibility very similar to natural tissue, due to their significant water content. 19

20. Conclusion Hydrogels are three-dimensional, hydrophilic, polymer network capable of imbibing large amounts of water or biological fluids. Hydrogels have many types, and have many properties as swelling behavior in aqueous solution. They can be used in contact lenses, drug delivery etc. 20

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