Polydisulfides

Montaudo and co-workers [12] identified the volatile products upon the thermal degradation of polystyrene disulfide using Py-MS and flash Py-MS. Using Py-MS they identified cyclic styrene disulfide, diphenyldithiene, styrene, and by flash Py-MS they identified cyclic styrene disulfide, cyclic styrene disulfide and diphenylthiophene, the latter compound not being found in direct Py-MS experiments. 

Chen and co-workers [13] have carried out studies on the thermal decomposition of aromatic disulfide oligomers using a variety of techniques. 

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Figure 4 The effect of stabilizer concentration on the induction period of polypropylene thermal oxidative breakdown (temperature 200°C P02 = 300 Tor). 1-polyamineani-line disulfide 2-polydiiminodiphenyloxide disulfide 3-polythiosemicarbazide disulfide 4-Santanox 5-hydroru-beanic polydisulfide 6-thiocarbamidepoly disulfide 7-po-lydisulfide.

Moreover, the reactions of an excess of thiirane with W(CO)s(NCMe) catalyst led to the formation of the cyclic polydisulfides as depicted in Fig. 58 [187],... 

Organic polydisulfides were combined with lithium metal in solid-polymer electrolytes [102-105] cf. No. 17 in Table 10 and Section 2. The cells were cycled at 80 °C. 

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. 

Monosulfide polymer 19 is the most stable of the polymers discussed, not only in its resistance to base, oxidizing acids, and light but also in thermal stability. Degradation is slow at 300°C, but at 350°C chain scission results in an unzippering to evolve tetrafluoroethylene and di-thietane 6 (n = 2). The latter gives rise to polydisulfide 16 and may cycloadd to tetrafluoroethylene to form dithiane 7, the third major product. More likely under these conditions, however, is direct formation of 7 by a backbiting mechanism as illustrated below. 

Metal carbonyl complexes show rich reactivities toward thiiranes and thietanes [134]. Reaction of W(CO)5(NCMe) with thiirane results in the ligand exchange reaction to give W(thiirane)(CO)5 (Scheme 3.70) [135]. This complex catalyzes formation of cyclic polydisulfides with olefin elimination (Scheme 3.71). 

This catalysis involves (l,2-ethanedithiolato)tungsten intermediate, which can be trapped by the addition of dimethyl acetylenedicarboxylate (DMAD). Interestingly, in the presence of DMAD, the formation of cyclic polydisulfides is greatly suppressed, and the cyclic polythioethers (thiacrowns) are mainly formed (Scheme 3.72). 

Marvel and Olson [36] further developed the oxidation polymerization technique that was earlier reported by Patrick [37] to give polydisulfides. 

When a dimercaptan was dispersed in an aqueous soap solution and air was passed through the mixture, oxidation to a polydisulfide readily occurred and a stable polymer latex was produced. Foaming was troublesome, but the addition... 

The polydisulfide derived from the dimercaptan that was prepared by adding 2 moles of thiolaeetic acid to 4-vinyl-1-cyclohexene with hydrolysis was heated... 

Preparation of a Polydisulfide by the Oxidation of Hexamethylenedithiol with Bromine [36] ... 

TABLE V Polydisulfides Prepared by Air Oxidation in the Presence of Selenious Acid°... 

More recently, the oxidation of mono- and dimercaptans to disulfides has been reported [38, 39]. The dimercaptans afford polydisulfides whereas the monomercaptans give disulfides [39]. 

Lu ZR, Mohs AM, Zong Y, Feng Y. Polydisulfide Gd(III) chelates as biodegradable macromolecular magnetic resonance imaging contrast agents. Inti J Nanomed 2006 1 31-40. 

Polymers of = 1600—6500 with polydispersity 1.2—2.8 were prepared by addition of diolefins with dithiols and the following two-phase oxidation of the resulting polydisulfides. The effective oxidation (up to 92% of sulfoxide units) of polysulfides was conducted by using aqueous hydrogen peroxide in chloroform with or without heating. The formation of polysulfoxides was strongly supported by spectroscopic analysis. Poly(hexamethylene sulfoxide) obtained in this way was subject to Swern oxidation of primary or secondary alcohols, in which 1-octanol [111-87-5] and 6-undecanol [23708-56-7] were oxidized to give 1-octanal [124-13-0] and 6-undecanone [927-49-1], respectively, in quantitative yields (18). 

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 ... 

The question of the involvement of zinc in the actual reaction in which carbon-sulfur bonds are formed in the rubber chain remains the major unresolved problem in sulfur vulcanization. Polysulfidic pendent groups are formed initially in the absence of zinc [124,125], probably via accelerator polydisulfides [126,127]. 

Goethals, E. J., and Silis, C., Oxidation of dithiols to polydisulfides by means of dimethylsulfoxides, Makromol. Chem., 119, 249, 1968. 

Polydisulfides containing hydroxyl groups have been synthesized by condensing 3,3 -diamino-4,4 -dihydroxydiphenysulfone ... 

Also polymercaptals and polymercaptols were obtained from dithiols and aldehydes and ketones. Polydisulfides were prepared by air oxidation of... 

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. 

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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