Synthesis and characterization of copolymers of perfluoro(2-methylene-4,5- dimethyl-1,3-dioxolane) and perfluoro(2-methylene-1,3-dioxolane)

Amorphous perfluorinated polymers with outstanding unique properties have established a solid position in various fields, but less costly preparations are required for practical application. Here, copolymers of perfluoro(2-methylene- 4,5-dimethyl-1,3-dioxolane) I and perfluoro(2-methylene-1,3-dioxolane) II are synthesized, and the effect of composition on various properties is studied. The copolymers are found to be almost ideal random copolymers with monomer reactivity ratios of r₁ = 1.12 and r₂ = 1.32. When the amount of II is 0-70 mol%, the copolymers are completely amorphous, optically transparent, and soluble in fluorinated solvents. The glass transition temperatures (T_g) of the copolymers are lower than the sum of the products of the weight fractions of the monomer units and their respective T_g values, suggesting the presence of attractive intermolecular interactions in the homopolymer of I. The copolymers show low refractive indices (1.32-1.34) and high decomposition temperatures (>378 C), which are comparable with or even better than those of conventional amorphous perfluorinated polymers.