Gel

A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough.^[1]^[2] Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady state, although the liquid phase may still diffuse through this system.^[3]

Gels are mostly liquid by mass, yet they behave like solids because of a three-dimensional cross-linked network within the liquid. It is the cross-linking within the fluid that gives a gel its structure (hardness) and contributes to the adhesive stick (tack). In this way, gels are a dispersion of molecules of a liquid within a solid medium. The word gel was coined by 19th-century Scottish chemist Thomas Graham by clipping from gelatine.^[4]

The process of forming a gel is called gelation.

^ Khademhosseini A.; Demirci U. (2016). Gels Handbook: Fundamentals, Properties and Applications. World Scientific Pub Co Inc. ISBN 9789814656108.
^ Seiffert S., ed. (2015). Supramolecular Polymer Networks and Gels. Springer. ASIN B00VR5CMW6.
^ Ferry, John D. (1980). Viscoelastic Properties of Polymers. New York: Wiley. ISBN 0471048941.
^ Harper D. "Online Etymology Dictionary: gel". Online Etymology Dictionary. Retrieved 2013-12-09.

[1] Khademhosseini A.; Demirci U. (2016). Gels Handbook: Fundamentals, Properties and Applications. World Scientific Pub Co Inc. ISBN 9789814656108.

[2] Seiffert S., ed. (2015). Supramolecular Polymer Networks and Gels. Springer. ASIN B00VR5CMW6.

[3] Ferry, John D. (1980). Viscoelastic Properties of Polymers. New York: Wiley. ISBN 0471048941.

[4] Harper D. "Online Etymology Dictionary: gel". Online Etymology Dictionary. Retrieved 2013-12-09.

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