Dithio polymers

Hydantoin, 5,5-diaryl-2,4-dithio-methylation, 5, 444 Hydantoin, 1,3-divinyl-polymers, 1, 280 Hydantoin, 5-methylene-polymers, 1, 280 Hydantoin, 5-phenyl-2-thio-tautomerism, 5, 370 Hydantoin, thio-... 

In general, the reaction mechanism of elastomeric polymers with vulcanisation reagents is slow. Therefore, it is natural to add special accelerators to rubber compounds to speed the reaction. Accelerators are usually organic compounds such as amines, aldehyde-amines, thiazoles, thiurams or dithio-carbamates, either on their own or in various combinations. 

While in most of the reports on SIP free radical polymerization is utihzed, the restricted synthetic possibihties and lack of control of the polymerization in terms of the achievable variation of the polymer brush architecture limited its use. The alternatives for the preparation of weU-defined brush systems were hving ionic polymerizations. Recently, controlled radical polymerization techniques has been developed and almost immediately apphed in SIP to prepare stracturally weU-de-fined brush systems. This includes living radical polymerization using nitroxide species such as 2,2,6,6-tetramethyl-4-piperidin-l-oxyl (TEMPO) [285], reversible addition fragmentation chain transfer (RAFT) polymerization mainly utilizing dithio-carbamates as iniferters (iniferter describes a molecule that functions as an initiator, chain transfer agent and terminator during polymerization) [286], as well as atom transfer radical polymerization (ATRP) were the free radical is formed by a reversible reduction-oxidation process of added metal complexes [287]. All techniques rely on the principle to drastically reduce the number of free radicals by the formation of a dormant species in equilibrium to an active free radical. By this the characteristic side reactions of free radicals are effectively suppressed. 

Vandenbergh J, Dergent J, Conings B, Gopala Krishna T, Maes W, Cleij TJ, et al. Synthesis and characterization of water-soluble poly(p-phenylene vinylene) derivatives via the dithio-carbamate precursor route. Eur Polym J 2011 47(9) 1827-35. 

Development of xanthate and dithiocarhamate derivatives overcomes several drawbacks of the sulfonium monomer (Scheme 7.2b and c). Xanthates and dithiocarbamates are easily prepared by the reaction of bis(halomethyl)benzene with alkylxanthate and dialkyldithiocarbamate salts respectively. Both precursors are stable at room temperature and soluble in organic solvents. This means the polymerization of these monomers can be performed in organic solvents e.g. THE) with the addition of alkoxide base e.g. potassium tert-butoxide). For the dithiocarhamate precursor, lithium bis(trimethylsilyl)amide can be used as the base and the polymerization proceeds at 35 The elimination temperature of these precursor polymers is typically lower than that of the sulfonium polymers with xanthate elimination at 160-250 °C and dithio-carbamate at 180 °C. It has been found that elimination of dithiocarbamate gave materials with reduced structural defects. Both xanthate and dithiocarbamate routes avoid the corrosive acid byproducts (HCl) present in the sulfonium elimination. This is particularly advantageous in device fabrication as adds have a negative impact on indium tin oxide electrodes and interfaces. ... 

Both HTS and BDTCH can be classified as proceeding through the mechanism, which forms heat-stable cross-links that are more resistant to scission. The cross-link has been referred to as a hybrid cross-link in which a hexylmethy-lene dithio group —S —[(CH2)e—S ] — is the bridging group between two polymer chains (45-49). In this scheme, k is presumed to be small. At high sulfur... 

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