Polymerization episulfide

Ethylene and propylene episulfides polymerize in THE at 0-70°C in the presence of sodium naphthalene, and (importantly) the polymer contains no naphthalene residues. The reaction involves one-electron transfer followed by dimerization of the resulting radical to give a dithiolate ion. This ion then polymerizes an episulfide by anionic mechanism (Boileau et al. 1967 Scheme 7.14). 

Ethylene and propylene episulfides polymerize in THF at 0-70°C in the presence of sodium naphthalene, and the polymer contains no naphthalene residues. The reaction involves one-... 

The 1,2-0-isopropylidenehexofuranose 5,6-trithiocarbonates undergo desulfurization with Raney nickel in the same manner as do the 5,6-episulfide analogs, with the formation of 5,6-dideoxy-l, 2-0-isopropylidene- t-D-a 2/Zo-hexofuranose (90). The 5,6-episulfides polymerize in aqueous alkali, presumably by a sequential, episulfide-cleavage reaction caused by thiolate anion and, for example, compound (84) gives a polymer, formu-... 

Another effective stereoelective catalyst for both epoxide and episulfide polymerization is the reaction product of R-(or S-) t-butylethylene glycol with diethylzinc (33). 

Phosgene reacts exothermically with thiirane in two steps (Scheme 36) (77MI50602). 3,5-Dinitrobenzoyl chloride and benzoyl fluoride initiate polymerization of thiirane. A novel reaction of benzoyl isocyanate or trichloroacetyl isocyanate, which yields ethylenethiol derivatives from epithiochlorohydrin (2-chloromethylthiirane), 2-methylthiirane or cyclohexene episulfide, has been reported (Scheme 37) (71BAU2432). 

Treatment of thiiranes with lithium aluminum hydride gives a thiolate ion formed by attack of hydride ion on the least hindered carbon atoms (76RCR25), The mechanism is 5n2, inversion occurring at the site of attack. Polymerization initiated by the thiolate ion is a side reaction and may even be the predominant reaction, e.g. with 2-phenoxymethylthiirane. Use of THF instead of ether as solvent is said to favor polymerization. Tetrahydroborates do not reduce the thiirane ring under mild conditions and can be used to reduce other functional groups in the presence of the episulfide. Sodium in ammonia reduces norbornene episulfide to the exo thiol. 

The (TPP)A1X family of initiators has been used to initiate the polymerization of a range of other monomer classes including epoxides, episulfides, and methacrylates.776 In the latter case the propagating species is an aluminum enolate and this too may initiate the ROP of lactones, such as 6-VL, albeit slowly. In this way a block copolymer P(6-VL)-b-PM M A of narrow molecular weight distribution (Mw/Mn= 1.11) has been prepared.787... 

The 3- and 4-membered cyclic sulfides, referred to as thiiranes (also episulfides) and thie-tanes, respectively, are easily polymerized by both cationic and anionic initiators, such as... 

Boileau, S., Anionic Ring-Opening Polymerizations Epoxides and Episulfides, pp. 467 487 in Comprehensive Polymer Science, Vol. 3, G. C. Eastmond, A. Ledwith, S. Russo, and P. Sigwalt, eds., Pergamon Press, London, 1989. 

The stereochemistry of ring-opening polymerizations of episulfides, lactones, lactides, IV-carboxy-a-amino acid anhydrides, and other monomers has been studied but not as extensively as the epoxides [Boucard et al., 2001 Chatani et al., 1979 Duda and Penczek, 2001 Elias et al., 1975 Guerin et al., 1980 Hall and Padias, 2003 Imanishi and Hashimoto, 1979 Inoue, 1976 Ovitt and Coates, 2000 Spassky et al., 1978 Zhang et al., 1990]. 

Living and Immortal Polymerizations of Episulfide Initiated with Zinc Porphyrin [79]... 

Copolymerization is a facile method to diversify the structure of polymer materials. However, if the polymerizabiHties of comonomers are far from each other, copolymerization is essentially difficult, resulting in the formation of a mixture of the homopolymers and/or the copolymer with block sequences. This is the case for the anionic copolymerization of epoxide and episulfide, where the po-lymerizabihty of episulfide is much higher than that of epoxide, and the copolymer consisting mostly of -S-C-C-S- and -O-C-C-O- homo sequences is formed [87]. As mentioned in the previous sections, the zinc complex of /-methylpor-phyrin brings about polymerization of both epoxide and episulfide. 

The potential use of the reaction was examined, but the episulfides decompose partially during the process, and the yield of cyclohexene episulfide under optimum conditions was 20%. Since episulfides may be obtained in much higher yields from the photodecomposition of COS to give triplet sulfur atoms in gas-phase reactions,26 the method hardly has synthetic importance. It was assumed that the low yield is due to deactivation of the sulfur atoms by collision with solvent molecules, causing them to polymerize to molecular sulfur instead of reacting with cyclohexene.22... 

Tsuruta, T. and Kawakami, Y., Anionic Ring-opening Polymerization Stereospecificity for Epoxides, Episulfides and Lactones , in Comprehensive Polymer Science, Pergamon Press, Oxford, 1989, Vol. 3, pp. 489-500. 

As an example of first block obtained by ionic polymerization, Tung et al. [118] have synthesized an a,co-polybutadiene, the end-groups of which were deactivated onto episulfide in order to generate a telechelic polybutadiene dithiol. Such a compound was successfully used to initiate the copolymerization... 

---