1. Hydrogels: Special Polymers

2. Examples of Hydrogels http://www.robaid.com/wp-content/gallery/medicine- 1/hydrogel-lenses-could-help-diabetics.jpg Contact lenses http://www.womansday.com/var/ezflow_site/storage/ images/wd2/recipes/tutti-frutti-gelatin-mold/190937-1- eng-US/tutti-frutti-gelatin-mold_slideshow_image.jpg Gelatin http://www.medgadget.com/archives/img/hydron_sm.jpg Drug delivery http://www.foryoumedical.com/UserFiles%5C49%5C200907 10%5C79B26D5DD2D17DAB749FBA4D529D0293.jpg Wound dressing http://www.stevespanglerscience.com/img/cache/ bcb9b8db117ee64376aedaf7af3595ca/water-jelly- crystal-flower.jpg Soil moistener

3. Sodium alginate One of the components of the hydrogel that will be synthesized One of the components of the hydrogel that will be synthesized Long chain polymer – covalently bonded Long chain polymer – covalently bonded Sodium ions (Na+) ionically bonded to chain Sodium ions (Na+) ionically bonded to chain http://www.aapspharmscitech.org/articles/pt0803/pt0803072/pt0803072_figure1.jpg

4. Crosslinking Sometimes bonds can form between long chain polymers Sometimes bonds can form between long chain polymers Forms a network structure Forms a network structure Referred to as crosslinked polymers Referred to as crosslinked polymers

5. Crosslinking http://www.emeraldinsight.com/content_images/fig/2180130305001.png

6. Crosslinking How is the crosslinking in this example different from the crosslinking in the previous example? http://wiki.chemprime.chemeddl.org/images/9/97/Cross-Linked_Polymer.jpg

7. Crosslinking How is the crosslinking in this example different from the crosslinking in the previous example? http://wiki.chemprime.chemeddl.org/images/9/97/Cross-Linked_Polymer.jpg

8. Hydrogels Crosslinked polymers Crosslinked polymers Can trap large quantity of water in the network structure (“hydro”) Can trap large quantity of water in the network structure (“hydro”) Shrink when dried Shrink when dried

9. Hydrogels