Iniferters monofunctional

Polymers 14 and 15 seem to serve as bifunctional iniferters from their structures, but they eventually act as the monofunctional iniferters because of the difference in the chain-end structure (see Sect. 4 for details). 

Monofunctional Iniferter R-X > R-tMJj-X End-functional polymer, AB-type block copolymer... 

The A-B type iniferters are more useful than the B-B type for the more efficient synthesis of polymers with controlled structure The functionality of the iniferters can be controlled by changing the number of the A-B bond introduced into an iniferter molecule, for example, B-A-B as the bifunctional iniferter. Detailed classification and application of the iniferters having DC groups are summarized in Table 1. In Eqs. (9)—(11), 6 and 7 serve as the monofunctional iniferters, 9 and 10 as the monofunctional polymeric iniferters, and 8 and 11 as the bifunctional iniferters. Tetrafunctional and polyfunctional iniferters and gel-iniferters are used for the synthesis of star polymers, graft copolymers, and multiblock copolymers, respectively (see Sect. 5). When a polymer implying DC moieties in the main chain is used, a multifunctional polymeric iniferter can be prepared (Eqs. 15 and 16), which is further applied to the synthesis of multiblock copolymers. 

A controlled free radical polymerization process used by White [3] entailed preparing the monofunctional iniferter 2,3-dicyano-2,3-dimethyl butane by thermally decomposing azobisiso-butyronitrile and then heating the iniferter sufficiently to form two carbon centered radical residues. In this manner polymers were prepared having moderate molecular weights but narrow polydispersities. 

The tetrafunctional photoiniferter (DDC) was prepared by the reaction 1,2,4,5-tetrachloromethylbenzene with sodium JV,AT-diethyl-dithiocarbamate in ethanol at room temperature for about 24 hr and recrystallized from a benzene//i-hexane mixture (—1 1 v/v) the melting point is 125.5-126.3°C. Photopolymerization of MMA with the tetrafunctional iniferter (DDC) was compared with the bifunctional iniferter (XDC) and the monofunctional in-... 

Thiuram disulfides, described above as photoiniferters, can also act as thermal iniferters. The mechanism of the polymerization is the same and polymer chains are invariably end-capped at both ends with iniferter segments. The use of thiurams as thermal or photoiniferters for the preparation of block copolymers greatly depends on the quantum yield of dissociation. The synthesis of dithiocarbamate functional polymers by direct photolysis of the iniferters is limited due to the low quantum yield of dissociation, especially in the case of the thiuram disulfide (e.g., the quantum yield of dissociation (rf) of TD is 0.0025 in cyclohexane [81]). This very low value makes the photochemical dissociation much less attractive than the thermal one. It was suggested that better dithiocarbamate functionalization can be achieved by either thermal initiation with TD at 95°C or polymerization in the presence of AIBN as a thermal initiator and TD as a chain transfer agent. In the latter case, monofunctional or bifunctional TD-PSt were formed, depending on the mole ratio AIBN/TD. Interestingly, the quantum yield of BDC was found to be 0.06, which is 24 times higher than that of TD. Thus, BDC can be used both as a thermal initiator and as a photoiniferter [81]. 

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