Styrene polymerization with disulfide initiators

The data allows us to propose the following mechanism of styrene polymerization in the presence of peroxide initiators and aliphatic mercaptans the regulator interacts with the initiator forming organic acids, disulfides and other products disulfides in their turn begin interactions with the initiators but at a lower rate than mercaptans this reaction is proceeded by the faster consumption of the benzoyl peroxide in the presence of different mercaptans, but there was no increase of radical formation rate. 

The polymerization of cydic disulfides to polydisulfides has been reported in the 1940s and 1950s. In some cases the polymerizations occur spontaneously. Tobolsky et reported that l-oxa-4,5-dithiacycloheptane and l,3-dioxa-6,7-dithiacyclononane are polymerized by cationic initiators such as sulfuric acid or boron trifluoride. Davis and Fettes repotted the anionic polymerization of various cyclic disulfides. In the same period it was also described that cyclic disulfides can copolymetize with vinyl monomers such as styrene and butyl acrylate with AIBN as initiator. That the incorporation of the disulfide was due to copolymerization and not by chain transfer was established by comparing the thermal polymerization of styrene in the presence of dibutyl disulfide and in the presence of l-oxa-4,5-dithiacycloheptane. In the first case, the polymer contained 2 sulfur atoms per macromolecule as a result of transfer reactions and in the second case 4-20 sulfur atoms depending on the ratio of monomers. 

In aqueous solvent a hydrophobic environment was constructed by using a water-soluble and hydrophobic tri-block copolymer (Scheme 7). The central block is hydrophobic and composed of the copolymer of styrene and N-vinylimidazole (PSI), to which Cu ions can coordinate. This central block was synthesized by UV-irradia-tion polymerization bytelechelic initiator of bis(4-carbomethoxy-phenyl)-disulfide. The reaction of telechelic block with poly-(ethyleneoxide) gave the block copolymer PE0-PSI-PE0. 

Four main studies have been published on styrene in which the authors show that thiuram disulfides play the role of both initiator and counter radical. Otsu et al. [235] demonstrated with 51 and 52 (n = 2) compounds and model molecule 55 that the polymerization of styrene led to the formation of mono-and dithiuram telechelic PS with a behavior close to that of living radical polymerization ... 

In a preparation of triblock polyions, a radical polymerization of methacrylic acid was carried out in ethanol solution, at 30 C, with Z w(isopropylxanthogen) disulfide acting as initiator, chain transfer agent, and chain terminator, under uv-irradiation. The purified product was then used as a uv-initiator for the block polymerization of sodium styrene-p-sulfonate [72]. 

---