Reverse iodine transfer polymerization

Organotellurium-Mediated Radical Polymerization and Reverse Iodine Transfer Polymerization... 

Keywords emulsion polymerization miniemulsion polymerization reverse iodine transfer polymerization... 

Evolution of molecular weight M (A) and polydispersity index My,/Mn ( ) with monomer conversion in reverse iodine transfer polymerization of methyl methacrylate in toluene at 80 °C in the presence of AIBN as initiator... 

Figure 2 illustrates the effect of Cex on the evolution of PDI with monomer conversion. It shows that PDI lower than 1.4 can be attained at high conversion for Cex> 3. This is in agreement with the values of polydispersity of PS samples obtained by FTP or reverse iodine transfer polymerization (RITP) (see Section 3.06.4.1). ... 

Instead of a dormant species, a conventional radical initiator can be immobilized on the surface to conduct reverse LRP. Reverse iodine transfer polymerization (RITP) has been established in solution by Lacroix-Desmazes and colleagues [42-44] and Tatemoto and Nakagawa [38]. A conventional radical initiator such an azo compound (R-N=N-R) and molecular iodine (I2) are used as starting compounds then, the alkyl iodide (R-1) formed in situ is used for the polymerization. Wang... 

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). 

Lacroix and coworkers reported a reverse iodine transfer pol5mierization (RITP), where elemental iodine is used as a control agent in living radical polymerization [288]. Styrene, butyl acrylate, methyl acrylate, and butyl ot-fluoroacrylate were homopolymerized, using a radical catalyst and I2 as a chain transfer agent. Methyl acrylate was also copolymerized with vinyUdene chloride using this process. 

Besides the most common CRP methods used to control the radical polymerization of vinylic monomers, other techniques have been developed over the time, and have been tested in miniemulsion or emulsion polymerization as well. These methods are described in the corresponding chapters of this comprehensive. They are iodine transfer polymerization (ITP and the reverse method, RITP), organotelluriirm-mediated CRP (TeRP), and cobalt-mediated radical polymerization (CoMRP). 

Controlled/ Living radical polymerization (CRP) of vinyl acetate (VAc) via nitroxide-mediated polymerization (NMP), organocobalt-mediated polymerization, iodine degenerative transfer polymerization (DT), reversible radical addition-fragmentation chain transfer polymerization (RAFT), and atom transfer radical polymerization (ATRP) is summarized and compared with the ATRP of VAc catalyzed by copper halide/2,2 6 ,2 -terpyridine. The new copper catalyst provides the first example of ATRP of VAc with clear mechanism and the facile synthesis of poly(vinyl acetate) and its block copolymers. 

VAc has been successfully polymerized via controlled/ living radical polymerization techniques including nitroxide-mediated polymerization, organometallic-mediated polymerization, iodine-degenerative transfer polymerization, reversible radical addition-fragmentation chain transfer polymerization, and atom transfer radical polymerization. These methods can be used to prepare well-defined various polymer architectures based on PVAc and poly(vinyl alcohol). The copper halide/t is an active ATRP catalyst for VAc, providing a facile synthesis of PVAc and its block copolymers. Further developments of this catalyst will be the improvements of catalytic efficiency and polymerization control. 

ATRP), and reversible chain transfer catalyzed polymerizations " and (iii) degenerative transfer-based polymerization (with reversible addition-fragmentation chain transfer (RAFT) polymerization being the most successful technique but also including iodine-mediated polymerizations and polymerizations in the presence of tellurium or antimony compounds ). Most of these techniques are covered in detail in other chapters of this book. 

The ion of the type Cdl+ is called an intermediate ion. The effect of this kind of ionization would be to increase the directly measured or apparent transference number of die constituent Cd++, since the complex ion we have postulated would carry iodine in the reverse direction to the normal motion of that ion and thus reduce the measured transference number of that ion. Another possibility, and the one which probably occurs in solutions of this salt, is the ionization of the polymerized salt in the form of complex ions, of which the following equations represent two of the many possibilities ... 

Currently three systems seem to be the most efficient processes for conducting a CRP nitroxide mediated polymerization (NMP) (eq. 1 in Fig. 5), atom transfer radical polymerization (ATRP) (eq. 2 in Fig. 5) and degenerative transfer systems (eq. 3 in Fig. 5) such as reversible addition-fragmentation transfer (RAFT) or iodine degenerative transfer (IDT) processes (88-90). The key feature of all CRPs is the dynamic equilibration between active radicals and various types of dormant species. 

---