FREE-RADICAL RING-OPENING POLYMERIZATION OF CYCLIC ALLYLIC SULFIDES

A new type of ring-opening monomer has been investigated and found to undergo facile and efficient free-radical polymerization. The monomers are cyclic allylic sulfides with 6-methylene-1,4-dithiepane (3) and 3 -methylene-1,5-dithiacyclooctane (4) synthesized and investigated as t wo examples. 6-Methylene-1,4-dithiepane (3) is a clear oil and 3-methy lene-1,5-dithiacyclooctane (4) has a low, near ambient temperature mel ting point, and in contrast to many ring-opening monomers, they readil y survive exposure to moisture and aqueous acids and bases. These comp ounds were polymerized in bulk with complete ring opening to give high ly insoluble crystalline homopolymers of high molecular weight (M(w) c a. 500 000-700 000) with glass transition temperatures of ca. -30 to - 50 degrees C and melting points of ca. 100-130 degrees C. The homopoly mers and their 1:1 copolymer were characterized by FT-IR and high-temp erature H-1 and C-13 NMR spectroscopies, high temperature GPC, and DSC . They displayed volume shrinkages in the range expected of ring-openi ng monomers (4.5-8.5%) of their molecular weights in spite of the crys tallinity present in the final polymers.