Gas Transport Properties of the Crystalline Phase Controlled Its Orientation of Poly(4-methyl-1-pentene)

The gas permeation and diffusion properties of drawn and undrawn membranes of poly(4-methyl-1-pentene) (PMP) membranes were investigated in relation to the orientation of the crystal phase. From the results of infrared dichroism and X-ray diffraction, we conclude that the c-axis of PMP crystals are uniaxially oriented in the drawing direction. The permeation coefficients of these drawn membranes for relatively small gas molecules were smaller than those of the undrawn membranes with randomly oriented crystals. On the other hand, the permeation of large gas molecules is not effected by the orientation of the crystals. Furthermore, we found a diffusion anisotropy of the PMP crystals when investigating the diffusion behavior of the methane in PMP membranes by pulsed field gradient H-1 NMR.