Free radical polymerization double ring opening

Treatment of 2-methylthiirane with t-butyl hydroperoxide at 150 °C in a sealed vessel gave very low yields of allyl disulfide, 2-propenethiol and thioacetone. The allyl derivatives may be derived from abstraction of a hydrogen atom from the methyl group followed by ring opening to the allylthio radical. Percarbonate derivatives of 2-hydroxymethylthiirane decompose via a free radical pathway to tar. Acrylate esters of 2-hydroxymethylthiirane undergo free radical polymerization through the double bond. 

Finally, the unsaturated spiro ortho carbonates were been shown to undergo double ring opening in a free radical polymerization to introduce a carbonate group in the backbone of an addition polymer (19). 

Figure 8. Idealized structure of the polymer obtained by the free radical polymerization of SOCM by non-ring-opening and double ring-opening pathways.

Very recently, Bailey and Endo have enlarged the scope of the free-radical ring-opening polymerization.13 15> Several examples of their studies are described below. All the polymerizations are represented by the following general pattern of fundamental reaction. It is seen that the free-radical ring-opening by a P-scission mechanism is coupled with the addition of a free radical to the carbon-carbon double bond 13). 

Correlations of structures and reactivities require for the ring-opening polymerization as well as for other ionic polymerizations approaches differing from these in radical polymerization of the unsaturated monomers. This is because in radical polymerization free radicals are the unique chemical structure of the growing species and double bonds are the only chemical groups involved in polymerization (1), C ). ... 

Free-Radical Copolymerization of Vinyl Compounds with Unsaturated Heterocyclic Monomers. Free-radical ring-opening polymerization of cyclic ketenacetals and their nitrogen analogous occurs via formation of carbonyl bond at the expense of a less stable carbon-carbon double bond as depicted in Scheme 14 [49-56] ... 

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