Crosslinking of polymer

Protein thiol groups also react with water soluble carbodiimides. For example, pa-paine is modified at residue cysteine 25. Tyrosine residues are also modified with carbodiimides.  

Carbodiimides are also used to crosslink wool, hair in permanent wave composition, and bovin lutotropin. Similarly, carbodiimides are used as gelatin hardeners promoting crosslinking via a reaction of carboxyls with amino groups. Also, gelatin hydrogels are crosslinked with water soluble carbodiimides.  

Carbodiimides are also used as fixing agents. Eor example, intestinal glucagon has been preserved using water soluble carbodiimides. Eixation by carbodiimide treatment is also useful as an ultrastructure preservative for electron microscopy.  

Resin bound carbodiimides are used in the formation of diphenol monomers used in the synthesis of tyrosine derived pseudo polypeptides.  

A 1 1 mixture of a carbodiimide containing latex polymer (t-butylcarbodiimidoethyl methylmethacrylate) and a carboxylic acid containing latex polymer (2-ethylhexyl methacrylate) showed that polymer interdiffusion occurs faster than crosslinking. Also, cyclohexylcarbodiimidoethyl methacrylate and t-butylcarbodiimidoethyl methacrylate have been prepared, and these monomers are used to prepare carbodiimide functionalized latex particles for emulsion polymerization.  

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Unfortunately, reliable data on the equilibrium swelling and long-term stability of hydrogels obtained by this method are not available. It should be noted that crosslinking of polymers with metal ions is one of the few reactions which can be carried out directly in the soil medium, which is efficiently used, e.g., in oil recovery [65, 66]. 

Distinctly different approaches to avoid these problems and still achieve high viscosities were conceived and applied. The different approaches can be categorized as 1) preparation of emulsions or foams and 2) addition of crosslinkers to the polymer. Two separate processes which utilized crosslinking of polymer gelling agents were pursued. These are the use of secondary (or delayed) gelling agents and the use of metallic crosslinkers added on-site. 

The crosslinking of polymers in a binary membrane complex via covalent binding is a traditional method for improving the impact resistance of materials. Generally, high molecular crosslinkers have been successful (e.g., dextran dialdehyde... 

Figure 6.4 The preparation of nanostructured materials in solution evolves from (a) the classic examples of suspension, dispersion, or emulsion polymerization, to the methods that include the covalent crosslinking of select domains within supramolecular polymer assemblies (b) core crosslinking of polymer micelles (c) shell crosslinking of polymer micelles (SCKs) (d) nanocages from core-eroded SCKs (e) shaved hollow nanospheres from outer shell/core-eroded vesicles.

Note 1 In both network-forming polymerization and the crosslinking of polymer chains, the gel point is expressed as an extent of chemical reaction (c.f, gel time). 

Adhesives are used in everyday applications. Adhesives may be in liquid form or thick pastes. Their main mechanism is based on the polymerization or crosslinking of polymers, which gives rise to glue or other adhesive application. The degree of adhesion of such a process is determined by conventional technological tests. 

Crosslinking of polymers is usually applied to stabilize the macroscopic morphology or shape of a material. In most cases, it results in insoluble polymeric materials, e.g., for polymeric coatings. In the chemoenzymatic strategies towards polymer networks, the enzymatic step is exclusively applied to synthesize the... 

Henglein, A. Crosslinking of polymers in solution under the influence of y-radiation. J. Phys. Chem. 63, 1852 (1959). 

The physical or chemical crosslinking of polymers can be also realized in water-in-oil (W/O) emulsion systems. In this case, aqueous droplets of prepolymers are stabilized by oil-soluble surfactants in a continuous oil phase. Hyaluronan-based microgels were prepared by crosslinking of carboxylic units of hyaluronan with adipic dihydrazide in aqueous droplets [19]. Chitosan-based microgels were prepared by crosslinking of chitosan chains with glutaraldehyde in aqueous droplets [20-25],... 

The T and X subscripts on G refer to T- and X-junctions. Note that Pi is crosslinked. In a similar polymerization (Vollmert s example 4) 1,4-buta-dienediol is introduced along with monomer 3, and the last step in the synthesis involves a crosslinking of polymer 2. In his example 7, four different polymers are mixed. To conserve space, details are omitted. 

When a drug or a non-active incorporated ingredient has plasticizing property, a further increase of cohesion with crosslinking of polymers is also a necessary approach. Practically, ionic crosslinkers such as aluminum acetylacetonate and chemical crosslinkers such as polyfunctional isocyanate are commonly used. The cross-linking occurs at the site of carboxyl groups or hydroxyl groups on the polymer side chain that may recover the cohesion of the adhesive. 

Results and discussion. In the course of our studies on light induced crosslinking of poly (vinyl buty-ral), new class of effective photosensitizers, neimely organic sulphoxides, was discovered. f4l] It should be noted, that four years after our invention, the use diphenyl sulphoxide simultaneously with o-ethylbenzo-ine and H2O2 as effective sensitizer for crosslinking of polymers, was reported 3 ]. 

HippE PhotosensiUzed Crosslinking of Polymers TABLE I. The Rq> R>Rl case. 

Polystyrene alone or with photosensitizer was unaffected under photolysis conditions, apart from some yellowing, and polystyrene-blsmaleimlde solutions appear to be stable Indefinitely in the dark. Blsmalelmldes have beat used previously in peroxide-Induced crosslinking of polymers l however, polystyrene was reported to be unreactlve under these conditions. Thus, the crosslinking reactions described here are not free radical in nature and are best formulated according to Reaction 3. Blsmalelmldes have also been reported to accelerate the radlolysls-induced crosslinking of elastomers.—... 

The crosslinking of polymers can be achieved by three major react ions (1) polymerization of multifunctional monomers (e.g., tetraacrylates), (2) self-... 

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