Cumyl dithiobenzoate

Early reports focused on the dithiobenzoale RAFT agents (Z=Ph e.g. 171-180, Table 9.10).3S2 410 Cumyl dithiobenzoate (175) shows utility with S and (meth)acrylic monomers.38 However, retardation is an issue with the acrylates... 

Much has been written on RAFT polymerization under emulsion and miniemulsion conditions. Most work has focused on S polymerization,409-520 521 although polymerizations of BA,461 522 methacrylates382-409 and VAc471-472 have also been reported. The first communication on RAFT polymerization briefly mentioned the successful semi-batch emulsion polymerization of BMA with cumyl dithiobenzoate (175) to provide a polymer with a narrow molecular weight distribution.382 Additional examples and discussion of some of the important factors for successful use of RAFT polymerization in emulsion and miniemulsion were provided in a subsequent paper.409 Much research has shown that the success in RAFT emulsion polymerization depends strongly on the choice of RAFT agent and polymerization conditions.214-409-520027... 

Mercapto-terminated block copolymers and block terpolymers prepared by Tsuji [4] such as poly(acrylonitrile-b-butyl acrylate) and poly(acrylonitrile-b-butyl acrylate-b-ethyl acrylate), respectively, used the RAFT chain transfer agent cumyl dithiobenzoate. The block copolymer had a M of48,600 daltons. 

RAFT has also been used to prepare copolymers. The copolymerization of MMA with nBA in the presence of cumyl dithiobenzoate as the transfer agent resulted in a polymer with a gradient of composition along the backbone, well-defined molecular weights, and low polydispersities [53]. Several copolymers were made by degenerative transfer with alkyl iodides [133]. 

The development of molecular weights and polydispersities as a function of the conversion is exemplified in Figure 3.7 for the RAFT polymerization of methyl methacrylate in benzene solution, initiated by AIBN, with cumyl dithiobenzoate as the chain transfer agent. 

For MMA polymerization, the addition of a Lewis acid, specifically scandium triflate [Sc(OTf)3], is known to increase the fraction of isotactic triads and enhance the rate of polymerization. Similar stereocontrol was observed for RAFT polymerization with cumyl dithiobenzoate and Sc(OTf)3. However, these RAFT polymerizations gave only poor control over molecular weight and polydispersity. Our NMR analyses confirm that the poor... 

Numerous reports describing the successful RAFT polymerization of NIPAM have appeared [35]. For example, in 2000, Rizzardo et al. first reported the RAFT living radical polymerization of NIPAM by AIBN employing benzyl dithiobenzene or cumyl dithiobenzoate RAFT agents 1 (Fig. 2) [39]. Fukuda et al. synthesized block copolymers using these systems [40]. Subsequently,... 

Online NIR spectroscopy has been used to measure conversion versus time traces for cumyl dithiobenzoate (CDB)-mediated styrene bulk polymerizations up to 2.5 kbar. MMDs of the resulting polymer were determined by SEC. ° ... 

Figure 2 Typical molecular weight distributions for a conventional radical and a RAFT polymerization. Data shown are from gel permeation chromatography (GPC) analysis of polystyrene prepared by thermal polymerization of styrene at 110 °C for 16 h (Mp 324 000, Mw/Mp 1.74,72% conversion) and a similai olymerizahon injhe presence of cumyl dithiobenzoate (0.0029 M) (Mp14400, Mw/Mp 1.04,55% conversion). Reproduced from Moad, G. Rizzardo, E. Thang, S. H., Living Radical Polymerization by the RAFT Process. Aust J. Chem. 2005, 58, 379-410. ...

Addition of a dithioacid across an olefinic double bondP This procedure has been used to prepare cumyl dithiobenzoate (91) (Scheme 21). Electron-rich olefins (St, AMS, isooctene, and VAc) give the desired Markownikov addition (sulfur at substituted position). However, similar reactions with... 

In polymerization of methacrylates and styrene with cumyl dithiobenzoate (91), retardation may be observed that is directly correlated with consumption of the initial RAFT agent and which is strongly dependent on the RAFT agent concentration. Other dithiobenzoates (e.g., cyanoisopropyl dithiobenzoate (92)) and aliphatic dithioesters (e.g., cumyl 2-phenylethanedithioate (110)) have fewer issues with respect to retardation. The aliphatic dithioesters are also less active and offer poorer control, with methacrylates. 

RAET polymerization of styrene with cumyl dithiobenzoate (91) tmda very high presstne (Skbar) has been reported. ° At very high presstne, radical-radical termination is slowed and this allows the formation of higha molecular weight polymas and higha rates of polymerization than are achievable at ambient pressure. 

Poly(N,N-dimethylacrylamide) with controlled MW, low values for M /Mn, and a high proportion of meso dyads (approx. 85%) was prepared using ATRP (methyl 2-chloropro-pionate/CuCl/MeeTREN) and RAFT (with cumyl dithiobenzoate transfer agent) in the presence of Y(OTf)3. These systems were used for the first one-pot synthesis of stereoblock copolymers by RP. Well-defined stereoblock copolymers, atactic-l -isotactic poly(N,N-dimethylacrylamides), were obtained by adding Y(OTf)3 to either an ongoing RAFT or ATRP polymerization, started in the absence of the Lewis acid. "... 

---