Sulfide polymers oxidation

Sulfur(II)-containing compounds possess the reducing activity and react with hydroperoxides and peroxyl radicals [1-5]. They are employed as components of antioxidant additives to lubricants and polymers [30-35]. Denison and Condit [36] were the first to show that dialkyl sulfides are oxidized by hydroperoxides to sulfoxides and then to sulfones... 

Swern oxidations have been performed using the PEG2000 bound sulfoxide 34 as a dimethylsulfoxide (DMSO) substitute (reaction 13).49-50 Several alcohols were efficiently oxidized to their aldehydes or ketones using this reagent, oxalyl chloride, and triethylamine. Precipitation of the polymer with cold diethyl ether and filtration through a pad of silica afforded the desired oxidized products in very good yields and purities. The reduced sulfide polymer could be reoxidized to sulfoxide 34 with sodium metaperiodate and used again in reactions with no appreciable loss in oxidation capacity. 

Oxidative polymerization of aryl disulfides has been carried out under high dilution conditions for the preparation of cyclic arylene sulfides for synthesizing cyclic arylene sulfide polymers. The readily available diphenyl disulfide and dichloro disulfide with diphenyl sulfide, diphenyl ether, or p-xylene are useful monomers for the synthesis of the corresponding cyclic oligo(thio arylene)s. The reaction scheme is shown in Fig. 30 [101]. 

Thiokol A, Eihanite, Perdu ren. The first commercial poly-sulfide polymer, prepd from ethylene dichloride and sodium polysulfide. Sulfur content 84% d about 1.6. Mixes with natural rubber. Cured polymer retains unpleasant odor irritating fumes evolve during manuf. Stable to the usual organic solvents and dil mineral acids. Unstable to alkalies and oxidizing substances. Of low tensile strength and abrasion resistance. Not recommended where tropic or arctic climates prevail,... 

In most cases determined by 30°C in 0.2% solutions of the sulfide polymers in CHClj and of the oxide polymers in C H. For very low MW polymers 0.5% solutions were used. 

Many monomers respond to a specific class of initiator or initiating mechanism with the exclusion of all others. Isobutylene polymerizes only cationically, not anionically or free radically. It is highly probable, therefore, that an initiator that induces polymerization in isobutylene acts cationically. Acrylates and methyl methacrylate do not polymerize cationically, but free radically or anionically. Cyclic sulfides and oxides do not undergo a free radical polymerization. Alternatively, monomers can also be used to test an initiator, if different initiators lead to completely different polymer structures. 2-Vinyloxyethyl methacrylate is polymerized cationically be means of the vinyl group, anionically via the acrylic group, and free radically via both groups (cross-linked polymers). Another possibility consists of the copolymerization of two different monomers (see Chapter 22). Suitable pairs are shown in Table 15-4. 

Organotin Stabilizer n Any of an important class of stabilizers for PVC, notable for their high efficiency, compatibility, and imparting of clarity. The family includes sulfides and oxides of tin-alkyls or -aryls, organotins salts of carboxylic acids, organotins mercaptides, and trialkyl or triaryl tin alcoholates. Certain dioctyltin mercaptides and maleate compounds have been approved for food contact use. See also Di-n-Octyltin Maleate Polymer and Di-n-Octyltin-s,s bis(isooctyl mercaptoacetate). 

Reactions of dimethyl sulfide with oxidized polypropylene. Polymer Degradation and Stability, 41 (1992), p. 205 - 210... 

Sulfiir-containing compounds are used as components of antioxidative polymer and lubricant additives. The mechanism of their retardation effect was intensively studied in the seventies and turned out to be rather complicated. In this mechanism, the reaction of these compounds with hydroperoxides occn>ies the central place. In 1945, G. Denison was first to show that dialkyl sulfides are oxidized by hydroperoxides to sulfoxides, the latter are oxidized to sulfones... 

Numerous diamines and aromatic dianhydrides have been investigated. WhoUy aromatic Pis have been stmctiirally modified by incorporating various functional groups, such as ether, carbonyl, sulfide, sulfone, methylene, isopropjlidene, perfluoroisopropyUdene, bipyridyls, sdoxane, methyl phosphine oxide, or various combinations of these, into the polymer backbone to achieve improved properties. The chemistry and apphcations of Pis have been described in several review articles (4). 

In another process for the synthesis of PPS, as well as other poly(arylene sulfide)s and poly(arylene oxide)s, a pentamethylcyclopentadienylmthenium(I) TT-complex is used to activate -dichlorobenzene toward displacement by a variety of nucleophilic comonomers (92). Important facets of this approach, which allow the polymerization to proceed under mild conditions, are the tremendous activation afforded by the TT-coordinated transition-metal group and the improved solubiUty of the resultant organometaUic derivative of PPS. Decomplexation of the organometaUic derivative polymers may, however, be compHcated by precipitation of the polymer after partial decomplexation. 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

The polysulfide base material contains 50—80% of the polyfunctional mercaptan, which is a clear, amber, sympy Hquid polymer with a viscosity at 25°C of 35, 000 Pa-s(= cP), an average mol wt of 4000, a pH range of 6—8, and a ntild, characteristic mercaptan odor. Fillers are added to extend, reinforce, harden, and color the base. They may iaclude siUca, calcium sulfate, ziac oxide, ziac sulfide [1314-98-3] alumina, titanium dioxide [13463-67-7] and calcium carbonate. The high shear strength of the Hquid polymer makes the compositions difficult to mix. The addition of limited amounts of diluents improves the mix without reduciag the set-mbber characteristics unduly, eg, dibutyl phthalate [84-74-2], tricresyl phosphate [1330-78-5], and tributyl citrate [77-94-1]. 

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