Disulfides, cyclic, polydisulfides

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. 

Formation of polycatenane network has recently been suggested by Endo et al. during the thermal polymerization of cyclic disulfides such as 1,2-dithi-ane, where involvement of the cyclic polymers in the polydisulfide formed is proved by mass spectrometry [268] (Scheme 55). The elastic properties of the corresponding polydisulfide is believed to come from the polycatenane network structure. 

A new approach to the synthesis of aromatic polysulfides and polydisulfides consists of the preparation of polydisperse cyclic oligosulfides (or disulfides) followed by ringopening polymerization. In several publications [358-365] a Canadian research group has elaborated and described this approach in much detail. This approach may be subdivided into two classes of cycles and ring opening mechanisms ... 

Cyclic disulfides are also radically polymerizable monomers. Although they do not have a C-C double bond for accepting radicals, the homolysis of the S-S bond permits the formation of S radicals (Scheme 19). The resulting biradical undergoes polyaddition to afford polydisulfide. 

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