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学无止境zsf

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[交流] 【讨论】这个是凝胶吗？已有23人参与

第一次测凝胶含量。拍的照片如附件。我感觉像果冻的那一层是凝胶啊？可是我又把他们重新放到溶剂里之后，过段时间又没了。凝胶应该是不溶不熔的呀，怎么又溶了呢？我拍到的状态不是完全意义上的凝胶吗？只是个中间态？
有谁了解的呢，讨论一下吧

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cellulose1728

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不懂的能不能不胡说八道？

gel分chemcial gel 和physical gel。

http://en.wikipedia.org/wiki/Gel
gel (from the lat. gelu—freezing, cold, ice or gelatus—frozen, immobile) is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state.[1] By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional cross-linked network within the liquid. It is the crosslinks within the fluid that give a gel its structure (hardness) and contribute to stickiness (tack). In this way gels are a dispersion of molecules or particles within a liquid in which the solid is the discontinuous phase and the liquid is the continuous phase.

Types of gels
Hydrogels
Hydrogel (also called aquagel) is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. Hydrogels are highly absorbent (they can contain over 99% water) natural or synthetic polymers. Hydrogels also possess a degree of flexibility very similar to natural tissue, due to their significant water content. Common uses for hydrogels include

OrganogelsAn organogel is a non-crystalline, non-glassy thermoreversible (thermoplastic) solid material composed of a liquid organic phase entrapped in a three-dimensionally cross-linked network. The liquid can be, for example, an organic solvent, mineral oil, or vegetable oil. The solubility and particle dimensions of the structurant are important characteristics for the elastic properties and firmness of the organogel. Often, these systems are based on self-assembly of the structurant molecules.[2][3]

XerogelsA xerogel ( /ˈzɪərɵdʒɛl/) is a solid formed from a gel by drying with unhindered shrinkage. Xerogels usually retain high porosity (25%) and enormous surface area (150–900 m2/g), along with very small pore size (1-10 nm). When solvent removal occurs under hypercritical (supercritical) conditions, the network does not shrink and a highly porous, low-density material known as an aerogel is produced. Heat treatment of a xerogel at elevated temperature produces viscous sintering (shrinkage of the xerogel due to a small amount of viscous flow) and effectively transforms the porous gel into a dense glass.