3.3 -dimethylthietane, polymerization

The block copolymer of ethylene oxide and 3,3-dimethylthietane shows useful properties of complexing halogen and heavy metal salts (79MI51402). Thietanes can be polymerized with methylmagnesium iodide as well as with a variety of electrophiles such as methyl sulfate, trimethyloxonium tetrafluoroborate, triethylaluminum, boron trifluoride and phosphorus trifluoride (67IC1461, 67MI51400). Thietane (210) has been patented as a stabilizer for poly(vinyl chloride) (73USP3767615). 

NMR studies of the polymerization of THF, oxepane, 3,3-dimethylthietane, 2-methoxy-2-oxo-l,3,2-dioxaphosphorinane and 2-methyl-2-oxazoline revealed that the structures of the growing qj ies are the corresponding onium ions these structures are given in Table 7 (earlier, the first reaction products, formed upon initiation, were observed in the polymerization of THF ). 

The polymerization of cyclic sulfides and amines provided, although tentatively, some information on kp and kp. The equality k kp was found (the Kq value measured for an initiator used was further applied in the determimtion of a in polymerization studies) in the polymerization of 3,3-dimethylthietane in CgHsNOa and qualitatively for l-phenylmethyl-2-methyl-aziridine Small differences were found between kp and k (the macrocation being less... 

The polymerization of oxepane has provided very simflar results , Goethals has observed that in the polymerization of 3,3-dimethylthietane k, is also larger in CH2CI2 than in C6HsN02 >. 

The application of 300 MHz H-NMR to the polymerization of 3,3-dimethylthietane initiated with trialkyloxonium tetrafluoroborate (initiator concentration higher than 0.02 mole 1 ) permits polymeric sulfonium ions to be observed ... 

Direct H-NMR evidence of the transformation of the strained cyclic onium ions into the polymeric onium ions in the reaction involving growing species and macromolecules was discussed in Sect. 5.3.1 for 3,3-dimethylthietane. However on the basis of H-NMR one carmot distinguish whether the reaction proceeds intra- or inter-molecularly but the answer can be found by kinetic studies. 

Anionic polymerization of thietane and various 2-, 3- and polysubstituted thietanes has been achieved with alkali metals (Li, Na, K, Cs, Rb), naphthyl sodiumn-butyllithium, °" 1,4-dilithio-l, 1,4,4-tetraphenylbutane, and a thiolate anion.Treatment of 3-chlorothietane with aqueous sodium thiocyanate is said to give polymeric material.Polymerization of thietane has been effected with Grignard reagents.Thietane and substituted thietanes have been polymerized with dialkyl zinc reagents.A copolymer has been obtained by treating 2-methylthietane and styrene with -butyllithium a block copolymer has been derived from thietane and isoprene. " Copolymers of thietane and 3,3-dimethylthietane with pivalolactone have been reported. ... 

The study of the polymerization of thietan and its substituted derivatives has been undertaken relatively recently [131—134]. Detailed kinetic experiments have been reported by Goethals et al. [33, 130, 135—137] and, as we shall see, the results parallel closely those foimd in the polymerization of THF. Most of the work has been carried out using 3,3-dimethylthietan,... 

The similarity in the reactivities of free ions and corresponding ion pairs derived from the same cyclic monomer is more intriguing. Whereas ion pair reactivities are about 10 times smaller than corresponding free ion values in the anionic polymerization of vinyl monomers [39], and probably of the same relative proportions in cationic systems, the difference in cationic ring opening polymerizations is considerably less. For polymerization of THF in methylene chloride the factor is only 7, and for polymerization of 3,3-dimethylthietan, 40 in methylene chloride and 1 in nitrobenzene. Because the overall reactivity in cyclic monomer reactions is lower than for olefinic polymerizations, it might be expected that difference between free ion and ion pair reactivities, within one system, would also be less. However, this does not seem to be the whole answer. Plesch [44] has pointed out that in the polymerization of cyclic ethers and thietans (and presumably, therefore, other cyclic monomers)... 

Polymerization of cyclic amines proceeds usually with high activation energies, due to the high strength of the C—N bond. To attain significant rates (k 10-3 mol-1 1 s 1) requires temperatures from 30 to 100 °C for azetidines and about 200 °C for the less strained bicyclic six-membered amines quinuclidine and triethylenediamine 9). Cyclic sulfides polymerize more rapidly than amines but much slower than ethers of a comparable structure (e.g. for 3,3-dimethylthietane k, = 2 10-2 mol-1 1 s at 35 °C, which is at least 104 times lower than for 3,3-dimethyloxetane (cf. Adv. Polymer Sci. 37 (1980)). 

Block copolymers of methylthiirane with thiirane or with 2,2-dimethylthiirane have also been obtained by sequential polymerizations initiated in the first phase by 2-naphthylsulfonylmethylene anions.Cationic polymerization has found use in the conversion of 3,3-dimethylthietane to SH-ended oligomers which could be coupled with hydroxyl-ended POE chains by reaction with a diisocyanate, but attempts to obtain block polymers of this thietane by direct initiation with cationic polystyrene were not successful. 

Chloropropyl thioesters are formed by the reaction of thietan with acid chlorides. Hydrogen chloride alone gave a small amount of 3-chloro-propanethiol at room temperature but polymeric material at 30—100 Charge-transfer complexes of thietan with electron-acceptors such as maleic anhydride, tetranitromethane, or tetracyanoethylene are believed to be intermediates in polymerization. The cationic polymerization of 3,3-dimethylthietan has been described. Treatment of 2-thietanones with MeCOSCl gave l,2-dithiolan-3-ones. ... 

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