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 (Tg) of the copolymers are lower than the sum of the products of the weight fractions of the monomer units and their respective Tg 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.
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