Editing Gel (section)

==Composition==
Gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through [[surface tension]] effects. This internal network structure may result from physical bonds such as polymer chain entanglements (see [[polymer]]s)  (physical gels) or [[chemical bond]]s such as [[disulfide]] bonds (see [[thiomer]]s) (chemical gels), as well as [[crystallite]]s or other junctions that remain intact within the extending fluid. Virtually any fluid can be used as an extender including water ([[hydrogel]]s), oil, and air ([[aerogel]]). Both by weight and volume, gels are mostly fluid in composition and thus exhibit densities similar to those of their constituent liquids. Edible jelly is a common example of a hydrogel and has approximately the density of water.

===Polyionic polymers===
Polyionic polymers are polymers with an ionic functional group. The ionic charges prevent the formation of tightly coiled polymer chains. This allows them to contribute more to [[viscosity]] in their stretched state, because the stretched-out polymer takes up more space. This is also the reason gel hardens. See [[polyelectrolyte]] for more information.