New amorphous perfluoro polymers: perfluorodioxolane polymers for use as plastic optical fibers and gas separation membranes

Abstract

To address the need for perfluoro polymers with higher Tg, we have prepared and characterized various perfluorodioxolane monomers via direct fluorination of the hydrocarbon precursors. These monomers were readily polymerized in bulk or in solution initiated by perfluorodibenzoyl peroxide. The polymers obtained have relatively high Tg(~160°C) and exhibited low material dispersion. These polymers are completely amorphous and soluble in fluorinated solvents. The polymers are also chemically and thermally stable (Tg > 300°C). Thus, these perfluorodioxolane polymers may be used as plastic optical fiber material where high Tg is required, such as in automobile and aircraft application. These perfluorodioxolane polymers were also investigated for use as gas separation membrane. Among these polymers, the copolymer of perfluoro (2‐methylene‐1,3‐dioxolane) and perfluoro (2‐methylene‐4,5‐dimethyl dioxolane) showed superior gas separation performance compared with the commercial perfluoro polymers for a number of gas pair, including CO2/CH4, He/CH4, H2/CH4, and N2/CH4. Copyright © 2015 John Wiley & Sons, Ltd.

Dioxolane-Based Perfluoropolymers with Superior Membrane Gas Separation Properties

“…These results are consistent with literature data. , However, such a difference can also be partially caused by the molecular weight difference in these two polymers. T g increases with increasing molecular weight of poly­(PFMMD), , and the molecular weight of poly­(PFMD) is unknown.…”

“…Recently, we have reported a new series of fluoropolymers based on dioxolanes for use in membrane gas separations. ,,, These polymers were successfully fabricated into defect-free TFC membranes and showed superior separation properties for He/gas and H 2 /CH 4 . For example, TFC membranes based on poly­(perfluoro-2-methylene-4-methyl-1,3-dioxolane) (poly­(PFMMD) with the chemical structure shown in Figure ) showed a He permeance of 2160 GPU (1 GPU = 10 –6 cm 3 (STP)/(cm 2 s cmHg)) and He/CH 4 selectivity of 108, which represent a significant improvement over the properties of membranes based on Hyflon AD60 or Cytop for He recovery from natural gas .…”

Volumetric Properties and Sorption Behavior of Perfluoropolymers with Dioxolane Pendant Rings

“…Owing to the unique combination of physical–chemical properties, fluorinated polymers have attracted interest in the automotive, aerospace, electronics, and medical industries . Fluorine-containing polymers exhibit uncommon thermal and chemical stability and poor solubility in organic solvents, as well as peculiar surface, electrical, and optical properties. − In the early 1990s, amorphous, solvent soluble perfluoropolymers appeared in the market. , Among them, Teflon AF, Hyflon AD, and Cytop exhibit peculiar transport properties, low swelling in the presence of vapors and liquids, and superior resistance to physical aging, which makes them attractive for membrane applications. − For example, the solubility of light gases and hydrocarbon vapors in amorphous perfluoropolymers is unusually low, and this feature has been ascribed to unfavorable polymer–penetrant interactions. , Analogously to fluorinated liquids, perfluoropolymers exhibit low cohesive energy density, which leads to relatively high free volume fractions . This feature makes commercial perfluoropolymers highly permeable but moderately selective .…”

Perfluoropolymer/Molecular Sieve Mixed-Matrix Membranes

“…In the last few years, other amorphous and glassy PFPs have been synthesized and studied for gas separation: atactic poly(hexafluoropropene) [ 27 ], new perfluoro-1,3-dioxoles [ 28 ], homo- and co-polymers of perfluoro(2-methylene-1,3-dioxolane)s ( Figure 2 ) [ 29 , 30 , 31 ]. The latter class of PFPs looks extremely interesting for the preparation of gas separation membranes, with impressive separation factors, beyond the 2008 Robeson upper bound for the H 2 /CH 4 , He/CH 4 , CO 2 /CH 4 , and N 2 /CH 4 separations [ 30 , 31 ].…”