Hydrogels three dimensional network

Figure 10.1 Hydrogel three-dimensional network able to retain large amount of water.

Properties. SUica gel (see Eig. 8) is a coherent, rigid, continuous three-dimensional network of spherical particles of coUoidal sUica. Both sUoxane, —Si—O—Si—, and sUanol, —Si—O—H, bonds are present in the gel stmcture. The pores are intercoimected and fUled with water and/or alcohol from the hydrolysis and condensation reactions (40). A hydrogel is a gel in which the pores are filled with water. A xerogel is a gel from which the hquid medium... 

Hydrogels are water-containing polymers, hydrophilic in nature, yet insoluble. In water, these polymers swell to an equiUbrium volume and maintain thek shape. The hydrophilicity of hydrogel is a result of the presence of functional groups such as —NH2, —OH, —COOH, —CONH2, —CONH—, —SO H, etc. The insolubihty and stabiUty of hydrogels are caused by the presence of a three-dimensional network. The scope, preparation, and characterization of hydrogels has been reviewed (107). 

Nanogels are nanometer-sized hydrogel nanoparticles (less than about 100 nm) with three-dimensional networks of physically crosslinked polymer chains. They have attracted growing interest over the last decade because of their potential for applications in biomedical fields, such as DDS and bioimaging [246-249]. 

Hydrogels are three-dimensional networks of hydrophilic polymers. 

In summary, we described a system in which a backbone containing a highly polar group contains a degree of cross-linking. Put another way, the system is a three-dimensional network of water-soluble polymer and cross-linking that serves as the basis for all hydrogels, natural or synthetic. 

In the past few years, several publications on drug-loaded hydrogels for ocular iontophoresis revealed novel iontophoretic applicators using the drug-saturated gel approach. Hydrogels are a three-dimensional network of hydrophilic polymers able to retain a large quantity... 

Hydrogels, or water polymer gels, are modified, cross-linked polymeric formulations which form three-dimensional networks of hydrophilic polymers... 

A hydrogel consists of a cross-linked hydrophilic polymer swollen with water. The three-dimensional network formed is able to imbibe large amounts of water or... 

The hydrogel formed has a continuous structure, giving a three-dimensional network of pores filled with water. The total volume of pores per mass-unit is called the pore volume and is a specific characteristic of the gel type. It is a main characteristic of sihca hydrogels, that mechanical treatment like milling does not affect the pore structure. Even after ball-milling the hydrogel into submicron particles the structure is maintained [61]. 

Chitosan derivatives, charged or uncharged, can form three-dimensional networks under cross-linking (Wasikiewicz et al. 2006, Yoshii et al. 2003, Zhao and Mitomo 2009, Zhao et al. 2003). Some typical properties of these hydrogel materials formed from chitosan derivatives such as CM-chitosan and DHP-chitosan are selected to be introduced here. 

Hydrogel n. A three-dimensional network of a hydrophilic polymer, generally covalently... 

In order to create a super hydrogel (NC gel), the concept of the fabrication of a novel three-dimensional network structure is important. For example, the simple dispersion of inorganic nanomaterials such as silica, titania, clay, and CNT into the network of an OR gel hardly improved the mechanical properties, regardless of the kind and size (aspect ratio) of the nanoparticles and the dispersion uniformity, as shown in Fig. lb for clay (4 wt%)-dispersed ORl gel. Also, almost no reinforcement was observed for the systems with other kinds of nanoparticles. 

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