Preparation and gas transport properties of dense fluoroaniline copolymer membranes

The first evaluation of gas transport properties of dense polyfluoroaniline and fluoroaniline copolymer membranes was presented. First of all, a series of fluoroaniline copolymers containing different feeding ratio of ortho-fluoroaniline/aniline were prepared by oxidative copolymerizations in CaCl₂/HCl medium. These polymers were amorphous and could afford flexible films in high molecular weight, obtained by casting from solution. The results for gas transport properties of dense fluoroaniline copolymer membranes revealed that the gas permeation properties significantly increased as the feeding ratio of ortho-fluoroaniline/aniline in the polymer matrix increased. Examples of the increase in the permeability coefficient for O₂ and CO₂ at 30 °C were 40% and 140% for polyfluoroaniline as compared with polyaniline, respectively and the selectivity of gas pairs, such as O₂/N₂, and CO₂/CH₄ slightly decreased. In addition, the effect of fractional free volume (FFV) in as-prepared membranes was studied. It was indicated that the gas permeability increased from the result of FFV in the range of 0.167-0.175. The temperature dependence of permeability was also investigated by an Arrhenius-type equation. Effect of material composition on thermal stability and mechanical strength of as-prepared membrane samples were evaluated by thermogravimetric analyses and dynamic mechanical analyses, respectively.