Polymerization of α-methylene cyclic ethers

Abstract

α-Methylene cyclic ethers, 4-phenyl-2-methylene-1, 3-dioxolane(4-P-2-MD), 4, 4, 5, 5-tetramethyl-2-methylene-1, 3-dioxolane(TM-2-MD), 4, 5-diphenyl-2-methylene-1, 3-dioxolane(DP-2-MD), 2-phenyl-4-methylene-1, 3-dioxolane(2-P-4-MD), and 5-phenyl-2-methylene tetrahydrofuran(5-P-2-MTF), were synthesized, and their polymerization behavior under various conditions and chemical properties of the resulting polymers were investigated. Those five α-methylene cyclic ether compounds exhibited quite different polymerization behaviors depending upon the employed polymerization system. Radically, 4-P-2-MD, DP-2-MD and 2-P-4-MD polymerized well and cleanly with quantitative ring opening. 4-P-2-MD was polymerized with di-tert-butyl peroxide (DTBP) at 124℃ to give white powdery polymers. Furthermore, the ring opening in the polymerization was shown to occur in an essentially complete regioselective manner with cleavage forming the more stable secondary benzyl radical. In the radical polymerizations of TM-2-MD, higher temperatures or more dilute conditions favored ring opening. This monomer gave a polymer with about 80% of rings having undergone ring opening with DTBP at 100℃. The monomer DP-2-MD was polymerized radically and poly[$γ-(β,γ-phenyl)butyrolactone] resulted from complete ring-opening at all temperatures. Similar results were obtained for the polymerization of monomer 2-P-4-MD and at higher temperatures the extent of ring opening also increased. With DTBP at 120℃ in benzene the monomer 5-P-2-MTF polymerized to give viscous oily product in low conversion. It was determined by NMR spectra that this polymer contained both 90% of ketone linkage formed by ring opening and a 10% of cyclic structures. In the postulated mechanism of radical polymerization a radical attacks at first on the methylene group of the ring to form dialkoxy-or alkoxy radical and this radical rearranges in turn to the energetically more stable radical, thus generating growing secondary benzyl o...