Iodine-Transfer Polymerization

The history of iodine transfer polymerization may be traced back to telomerization experiments carried out in the 1940 s. Iodine-transfer 

17JIJ8 various fluoro-olefins. Narrow dispersity PS was not obtained and this can be attributed to the transfer constant (Ci, 3.6 at 80 °C). 

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Polymerization of S and certain fluoro-monomers in the presence of alkyl iodides provided the first example of the reversible homolytic substitution process (Scheme 9.35). This process is also known as iodine transfer polymerization (Section 9.5.4).381 Other examples of reversible homolytic substitution are polymerizations conducted in the presence of certain alkyl tellurides or stibines (Sections 9.5.5 and 9.5.6 respectively). 

There are essentially two methods used for the production of commercial FTPEs. The first is referred to as iodine transfer polymerization, which is similar to the living anionic polymerization used to make block copolymers such as styrene-butadiene-styrene (e.g., Kraton ). The difference is that this living polymerization is based on a free radical mechanism. The products consist of soft segments based on copolymers of vinylidene fluoride (VDF) with hexafluoropropylene (HFP) and... 

The cleavage of C l bond can be achieved by various methods [149-151]. However, from well-chosen monomers, two main ways have been developed in order to control telomerization from alkyl iodides Iodine Transfer Polymerization (FTP) and degenerative transfer. 

Several investigations have shown that iodine transfer polymerization can be processable by emulsion or radical initiations. When emulsion initiation is... 

If an overall conclusion could be made, it might be considered that the counterradicals vary considerably (Scheme 3). They can either be stable (e.g., nitroxyls, arylazooxyls), semi persistent (e.g., from thiourams) and also metallic (e.g., acetoacetato metals). In addition, if these radicals either terminate or transfer, non-living (or inactive) species will be produced. But, in order to preserve the living character, the radicals must propagate and in specific cases (e.g., iodine transfer polymerization or degenerative transfer) active species will be obtained. The more that one of these latter steps is favored, the more living is the tendency of the radical polymerization, with a very high kinetic control of this reaction. 

Modern polymerization techniques, such as sequential iodine transfer polymerization of fluoroalkenes [11,12], lead to novel thermoplastic elastomers (TPEs). These triblock copolymers can be produced in a process, which can be emulsion, suspension, microemulsion, or solution polymerization [13], Using pseudo-living technology or branching and pseudo-living technology, A-B-A phase separated copolymers with soft (amorphous) and hard (crystalline) domains can be produced. The hard domains can be composed from the following ... 

Hexamethyltriethylenetetraamine Isocyanoethyl methacrylate Iodine transfer polymerization Liquid chromatography Living radical polymerizations... 

Telechelic Oligomers Obtained by Iodine Transfer Polymerization... 

Scheme 41 Elementary steps of iodine transfer polymerization (ITP)...

Table 23 Characteristics of the macromonomers prepared by iodine transfer polymerization at various reaction times...

In this ca.se, the chain transfer step involves formation of an intermediate adduct. Other examples thought to involve a transfer by homolytic substitution are iodine transfer polymerization (Section 9.5.4) and TERP (telluride-mediated polymerization, Section 9.5.5). 

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