Synthesis and characterization of an amorphous perfluoropolymer: Poly(perfluoro-2-methylene-4-methyl-1,3-dioxolane)

A perfluorinated monomer, perfluoro-2-methylene-4-methyl-1,3-dioxolane (PFMMD), was synthesized by various methods. The monomer was polymerized in bulk and/or in the solution by a free radical mechanism using perfluorodibenzoyl peroxide and/or perfluorodi-ferf-butyl peroxide as an initiators. The polymers obtained (poly(PFMMD)) were colorless and transparent. However, a polymer rod exposed to the atmosphere turned hazy. When the polymers were purified by precipitating the polymer solution into chloroform, they did not turn hazy when exposed to air for a long period of time and remained clear with a high UV-vis light transmittance. The glass transition temperature of the purified polymer was 130-134 °C. NMR measurements indicate that the purified polymers have mostly vinyl addition polymer structure. Nevertheless, we suppose that the pristine polymers contain structural units formed by ring-opening polymerization. The molecular weight of poly(PFMMD) samples can be regulated using carbon tetrachloride, carbon tetrabromide, and sulfuryl chloride as chain transfer agents. Polymerization in the presence of these regulators is characterized by nondegradative chain transfer. The intrinsic viscosity of poly(PFMMD) samples was determined in hexafluorobenzene. Hexafluorobenzene is a thermodynamically good solvent for poly(PFMMD). The molecular weights of poly(PFMMD)s were characterized by the intrinsic viscosity and dynamic light scattering (DLS). The refractive index of poly(PFMMD) between 400 and 1550 nm was between 1.3360 and 1.3270. The material dispersion of poly(PFMMD) is superior to that of a commercial polyd,1,2,4,4,5,5,6,7,7-decafluoro-3-oxa-l,6- heptadiene) (Cytop).