Free-Radical Ring-Opening Polymerization of Cyclic Allylic Sulfides. 2. Effect of Substituents on Seven- and Eight-Membered Ring Low Shrink Monomers

The effect of substituents on the free-radical ring-opening polymerization behavior and polymerization volume shrinkage of the cyclic allylic sulfides 6-methylene-1,4-dithiacycloheptane (2a) and 3-methylene-1,5-dithiacyclooctane (2b) has been investigated. The monomers were 2-(hydroxymethyl)-6-methylene-1,4-dithiacycloheptane (3a), 6-methylene-1,4-dithiacycloheptan-2-ylmethyl acetate (3b), 6-methylene-1,4-dithiacycloheptan-2-ylmethyl methacrylate (3c), 7-methylene-1,5-dithiacyclooctan-3-ol (4a), 7-methylene-1,5-dithiacyclooctan-3-yl acetate (4b), 7-methylene-1,5-dithiacyclooctan-3-yl benzoate (4c), and the bicyclic monomer bis(6-methylene-1,4-dithiacycloheptan-2-ylmethyl) diglycolate (5). The monomers were polymerized in bulk with thermal (AIBN, VAZO88) and photochemical initiators (Darocur 1173) with selected solution polymerizations also performed. The presence of a substituent on the monomers gave clear amorphous polymers unlike the crystalline polymers obtained from the unsubstituted parent monomers (...