Cross-linking and Polymerization Reactions

Polymerization of methyl methacrylate monomer with cobalt-60 as source of y-rays, Free radical formation is involved in both cross-linking and polymerization reactions This technique is also being applied in the textile finishing field for grafting and cross-linking fibers with chemical agents for durable-press fabrics. 

Hydroperoxides. Hydroperoxides are generally unsuitable for cross-linking and polymerization reactions since the possibility of a side reaction, such as ionic decomposition, is too great. They are used as a raw material to manufacture other organic peroxides. The most common hydroperoxides include cumene hydroperoxide and f-butyl hydroperoxide. 

The design of such systems is based on the incorporation of photoaaive dye (chromophore) molecules into macromolecules of LC polymers, and these dye molecules undergo reversible or irreversible chemical transformations under the aaion of light, such as -Z (trans-cis) isomerization, cydization, dimerization, cross-linking, and polymerization reactions. 

Since activated molecules and cross-links formed between two species are identical to those formed using SPDP, it is of little advantage to use PDTP. Furthermore, an EDC-mediated reaction of the carboxylate end of the cross-linker with amine groups on proteins can cause concomitant zero-length cross-linking and polymerization of protein molecules. For these reasons, SPDP is the better choice for preparing conjugates. 

Etee-tadical reactions ate accompHshed using a variety of processes with different temperature requirements, eg, vinyl monomer polymerization and polymer modifications such as curing, cross-linking, and vis-breaking. Thus, the polymer industries ate offered many different, commercial, organic peroxides representing a broad range of decomposition temperatures, as shown in Table 17 (19,22,31). 

The final conclusion of this short discussion is that electropolymerization is a fast method (a film of about 5 //mean be obtained by polarization in 1 rnin) that uses a complex mechanism (Fig. 12) in which electropolymerization, cross linking, degradation, and chemical polymerization can coexist to produce a mixed material with a cross-linked and electroactive part and a passive fraction.67-71 However, ifwe control the variables acting on the kinetics of the different simultaneous reactions, the complexity also provides flexibility, allowing us to obtain materials tailored for specific applications. 

Note 2 Physical aging, crystallization, physical cross-linking, and post-polymerization reactions are sometimes referred to as curing . Use of the term curing in these cases is discouraged. 

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