Term: gel
https://doi.org/10.1351/goldbook.G02600

Definition:
Non-fluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid.

Notes:
0) A gel has a finite, usually rather small, @Y06727@.
1) A gel can contain: a covalent @P04742@, e.g., a @NT07562@ formed by @CT07136@ polymer chains or by non-linear @P04740@;a @P04742@ formed through the physical aggregation of polymer chains, caused by hydrogen bonds, @C01434@, @H02769@ formation, complexation, etc, that results in regions of local order acting as the @NT07562@ junction points. The resulting swollen @NT07562@ may be termed a @TT07531@ if the regions of local order are thermally reversible;a @P04742@ formed through glassy junction points, e.g., one based on @B00682@ copolymers. If the junction points are thermally reversible glassy domains, the resulting swollen @NT07562@ may also be termed a @TT07531@;lamellar structures including mesophases, e.g., @S05721@ gels, @P04559@ and clays;particulate disordered structures, e.g., a flocculent precipitate usually consisting of particles with large geometrical @AT06776@, such as in V2O5 gels and globular or fibrillar protein gels.
2) Corrected from previous definition where the definition is via the property identified in Note 1 (above) rather than of the structural characteristics that describe a gel.

Related Terms:
1) yield stress (http://doi.org/10.1351/goldbook.Y06727).
2) polymer network (http://doi.org/10.1351/goldbook.P04742).
3) network (http://doi.org/10.1351/goldbook.NT07562).
4) crosslinking (http://doi.org/10.1351/goldbook.CT07136).
5) polymerization (http://doi.org/10.1351/goldbook.P04740).
6) crystallization (http://doi.org/10.1351/goldbook.C01434).
7) helix (http://doi.org/10.1351/goldbook.H02769).
8) thermoreversible gel (http://doi.org/10.1351/goldbook.TT07531).
9) block (http://doi.org/10.1351/goldbook.B00682).
10) soap (http://doi.org/10.1351/goldbook.S05721).
11) phospholipids (http://doi.org/10.1351/goldbook.P04559).
12) anisotropy (http://doi.org/10.1351/goldbook.AT06776).
13) colloidal network (http://doi.org/10.1351/goldbook.CT07563).

Source: PAC, 2007, 79, 1801. 'Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007)' on page 1806 (https://doi.org/10.1351/pac200779101801)

Citation: 'gel' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.G02600

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