Polyfunctional iniferters

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. 

When the polyfunctional iniferter 50 which has several DC units in the main chain was used, multiblock copolymers of St and VAc were easily prepared, as shown in the following equation [185] ... 

Polyfunctional iniferters have also been employed to prepare branched, network and star polymers (8-10, Chart 3.3). For example, Ishizu et showed that functionalized iniferters ((A, A -diethyldithiocarbamyl) methyl styrene or 2-(A, A -diethyldithiocarbamyl)ethyl methacrylate) can be utilized for the synthesis of hyperbranched polymers (UV irradiation), star polymers (copolymerization of vinyl head with crosslinking agent in dark condition), and rigid polymer brushes (vinyl homopolymerization of macroiniferters and subsequent treatment by internal domain locking with diamine compounds). 

Scheme 3.10 Synthesis of hyper-branched polymers using polyfunctional iniferters.

---