It is also referred to as "
Aquagel".
An extremely hydrated polymer gel i.e. colloidal gel giving a jelly like appearance. The polymer chain holds many times its weight in trapped water [1] which can be upto 99%. Hydrogel has water as the dispersion medium or continuous phase.
(N. A. Peppas et al.) Hydrogels resemble, to a large extent, a biological tissue as they are hydrophilic and have the ability to imbibe large amounts of water and other biological fluids. They have a three dimensional macromolecular network. They are insoluble due to chemical and/or physical crosslinking as entaglements and crystallites. The crosslinks are formed by covalent bonds.
Components of hydrogel:
Hydrogel is made by the combination of a hydrophilic component and water i.e.
Hydrogel = Hydrophilic component + Water
Types:
Hydrogels are
1. natural (Methylcelloluse and agarose)
2. synthetic (Polyacrylamide and polymetha-acrylamide)
(E. Tichy et al.) Two different types of hydrogels:
2. Second based on Polyacrylamide.
Two factors responsible for the extent of swelling and for retaining the water content are as follows:
1. The hydrophilicity of the polymer chain.
2. The crosslinking density. [2]
Properties of Hydrogels:
(Stephen D. Bruck) Properties that can be used to differentiate the hydrogels are
1. Permeability and diffusion co-effecients
2. Some role of quasiorganized water within the hydrogels.
3. Porosity.
4. Presence of functional groups.
5. Types and number of crosslinks.
6. Chemical entities.
Uses:
Hydrogels are very absorbent in nature.
They are also used in sustained release drug delivery systems.
by Bipin Paracha
