ORIENTATION TEXTURE AND GAS TRANSPORT IN SEMICRYSTALLINE BLOCK COPOLYMER BLENDS

The shear-induced morphologies produced by plane strain compression, using a channel die, were investigated in semicrytalline ethlylene/ethylene-opylene (E/EP/E and H/HP) block copolymers blended with semicrystalline low density polyethylene and amorphous polyisoprene homopolymers. Two dimensional small-angle x-ray scattering (SAXS) was used to determine the lamellar orientation relative to the specimen boundaries. Using a cooling rate of 0.27 °C/s and a load of 9.2 MPa. a normal to the plane of shear microstructure orientation texture was produced in the blends. The E homopolymer chains co-crystallize within the confinement of the oriented microphase separated E block copolymer domains. The long period spacing of the oriented microphase separated K/F.P block microstructure remained unchanged, while the spacing associated with the crystallization of the E chains increased with increasing weight percent of E homopolymer in the blend. Gas permeability coefficients for He and CO2 were measured for isotropic and oriented blends. The separation properties of these polymer systems was altered by changing the mechanism of gas transport, A selective solvent was used lo develop a uniform porous structure in the oriented blend morphologies. The semicrystalline block copolymer blend structure oriented perpendicular to the direction and normal to the plane of shear presents the opportunity lo create a high flux porous structure, while keeping the pores of nanometer dimensions, thus providing some selectivity and retaining mechanical strengtii.