Permeability relationships of polyimide copolymers

The permeability of the homopolymers 6FDA‐3BDAF and 6FDA‐4BDAF and of the copolymers 6FDA‐4/2BDAF, 6FDA‐4/3BDAF, and 6FDA‐4/3/2BDAF to He, CO2, and CH4 was measured at 35.0°C and at pressures up to 10 atm. The experimental values of the permeability coefficients for the copolymers are in satisfactory agreement with the values estimated from the permeability coefficients for the constituent homopolymers and their weight fractions. The synthesis of the fluorine‐containing diamine 2BDAF is reported for the first time.