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Gels as thickeners
A crucial process in the thickening effect is the formation of a gel. Gels mostly consist of a solid, colloidally distributed substance with long or highly branched particles, the gelling agent, and a liquid, the dispersing agent. The solid substance in the dispersant forms a spatial network, the particles being connected to one another by minor or major valences. A polymer gel is a polymeric network swollen in a liquid medium.
The properties of the gels depend on the interaction between the network and the surrounding liquid. If the networks are hydrophilic polymers and water is used as the swelling medium, one speaks of hydrogels. The affinity of the polymer network for water is based on the hydration energy, through which the water molecules are attached, and the polymer entropy, which is used to expand or "unfold" the When dry, it leads to coiled polymer molecules. When the polymer coil expands, it binds water molecules.
The hydrogels are widespread in nature. In the human body they are mostly found as cross-linked mucopolysaccharides in connective tissue and cornea. The surfaces of the internal organs such as the lungs and stomach are also coated with hydrogels. There they protect the lungs from dehydration or the stomach walls from the very aggressive digestive juices. In addition, they play a crucial role in the transport of oxygen, water and dissolved molecules. A slight change in their viscoelastic properties leads, for example, to a serious, often fatal disease, cystic fibrosis.