Gel

Polymer science
Properties Architecture Tacticity Morphology Degradation Phase behavior Mark–Houwink theory UCST LCST Flory–Huggins solution theory Coil–globule transition
Synthesis Chain-growth polymerization Free-radical polymerization Controlled radical polymerization ATRP RAFT Nitroxide-mediated radical polymerization Step-growth polymerization Condensation polymerization Addition polymerization
Classification Functional type Polyolefin Polyethylene Polypropylene Polyisobutylene Polyurethane Polyester Polycarbonate Vinyl polymers PVC PVA PVAc Polystyrene Structure Homopolymer Copolymer Gels Hydrogels Self-healing hydrogels
Characterization GPC FTIR X-ray crystallography DSC NMR TGA DMA Rheology Rheometry Viscometry
Scientists Flory Heeger MacDiarmid Shirakawa Natta Edwards de Gennes Ziegler Staudinger Goodyear Baekeland Hayward Braconnot
Applications Industrial production Extrusion Blow molding Applied coatings Protective Coatings 3D printing Consumer products Tires Whitewalls Cookware and bakeware Bakelite Food Container Vinyl record Kevlar Plastic bottle Plastic bag
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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.