Synthesis and characterization of fluorene‐based polybenzimidazole copolymer for gas separation

Abstract

The purpose of this study is to develop new cardo‐polybenzimidazole (CPBI) copolymers containing cardo fluorene, with improved gas permeability, specifically oxygen permeability. The characteristics of these copolymers are investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance, 1H and 13C), thermo‐gravimetric analysis, and wide‐angle X‐ray diffraction. These membranes fabricated from copolymers have relatively high oxygen diffusion coefficients, determined using gas permeation. In particular, the CPBI‐co91 (synthesized by using the monomers ratio containing dibenzoic acid = 9 : 1) membrane have oxygen permeability coefficient (PO2) of 10.69 Barrer, theoretical selectivity of 5.4 for oxygen to nitrogen, and O2 diffusion coefficient of 9.64 × 10−8 cm2/s. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40521.

Eaton’s reagent in polybenzimidazole synthesis

“…The spectrum of the polymer formed at 180°C after 7 min of polycondensation is very similar to the 1 H NMR spectra of OPBIs previously reported, and the signals were assigned according to the literature. 10,11,27 Practically the same signals were observed in the 1 H NMR spectrum of the polymer obtained in 2 min at 180°C; however, the relative intensities were slightly different, particularly for the signal corresponding to H–N at 13 ppm. In contrast, the signals in the spectrum of OPBI formed at 140°C in 2 min and even in 7 min were not so well defined because of incomplete formation of the benzimidazole heteroring that coincides with our FTIR data interpretation.…”

“…1 –3 In the recent years, PBIs have been attracting steadily increasing interest because of their possible applications in high-temperature proton exchange membrane fuel cells 4 –7 and as membranes for gas separation under severe conditions, for example, in a natural gas sweetening industrial process. 8 –11…”

A highly selective polybenzimidazole‐4,4′‐(hexafluoroisopropylidene)bis(benzoic acid) membrane for high‐temperature hydrogen separation

“…20 Since PBI-HFA polymer with large d-spacing and inner pores could show enhanced gas permeability, we initially determined the d-spacing of the as-prepared PBI-HFA polymer in the film form using wide-angle X-ray diffraction (WAXD). 27 Glassy polymers have different types of free volume, and the diffusion mechanism in glassy polymer membranes will depend on the nature of the free volume and the polymer backbone chain flexibility. The details on the fabrication of m-PBI membranes were described in our previous article.…”

Recent progress in microporous polymers from thermally rearranged polymers and polymers of intrinsic microporosity for membrane gas separation: Pushing performance limits and revisiting trade‐off lines

“…Recently reported cardo monomers or spiro monomers are mainly designed with adamantane [42][43][44][45] units or fluorene units. [46,47] The presence of such groups on the side chain in polymer backbones induces microporosity; however, those on the main chain even regulate polymer rigidity. Maya et al introduced three kinds of adamantyl ester pendant groups into the side chain of polyimides, resulting in a $19% increase in FFV with approximately threefold improvement in CO 2 permeability.…”