Cross linking in polymerization

Generally, the reactions that generate cross-links in polymeric systems are classified into two types, namely, those where cross-links are formed by the direct reaction of an excited molecule or group, and those where cross-links are formed through the action of a radiation-generated reactive species in the ground state. The following describes both types. 

The above results proved the potential viability of the adsorbed hydrophilic macromolecules as bonded phases in chromatography of biopolymers but it must be admitted that additional crosslinking of previously adsorbed macromolecules is usually needed in order to obtain stable composites. The cross-linked bonded polymeric phases, however, may suffer from the restricted flexibility of the chain segment and their steric repellency may be diminished. Moreover, the conformational adaptivity of cross-linked chains for binding with solutes is poorer than that of grafted or chemically bound macromolecules. 

Malencik, D.A. and Anderson, S.R., Dityrosine formation in calmodulin Cross-linking and polymerization catalyzed by Arthromyces peroxidase. Biochemistry, 35, 4375 386, 1996. 

In the most succinct sense, a hydrogel is simply a hydrophilic polymeric network cross-linked in some fashion to produce an elastic structure. Thus any technique which can be used to create a cross-linked polymer can be used to produce a hydrogel. Copolymerization/cross-linking free radical polymerizations are commonly used to produce hydrogels by reacting hydrophilic monomers with multifunctional cross-linkers. Water-soluble linear polymers of both natural and synthetic origin are cross-linked to form hydrogels in a number of ways ... 

Dense membranes are a special type of polymeric membranes. Jacobs et al. published on the use of polydimethylsiloxane (PDMS) dense membranes in the hydrogenation of dimethylitaconate and acetophenone using standard homogeneous catalysts (see Section 4.6.1)[48]. The membranes were homemade from a PDMS solution in hexane, which was cross-linked in a vacuum oven at 100°C. The membranes were able almost completely to retain unmodified Ru-BINAP dissolved in isopropanol. However, as mentioned earlier, these applications will strongly depend on the size, i.e. molecular weight, of the substrate to be converted in order to guarantee a sufficient difference in size of the product and the catalyst to be retained. 

I.4.2.I. Synthesis and Modification of Polymers Unstable bis(nitrile oxide), generated by dichloroglyoxime dehydrochlorination, polymerizes in solution to give poly(furoxan) or (in the presence of 1,3-dienes) gives rise to their being cross-linked (500). Polymerization of terephthalonitrile dioxide and its... 

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