Structural arrangement of crystalline/amorphous phases of polyethylene-block-polystyrene copolymer as induced by orientation techniques

A polyethylene-block-polystyrene copolymer film having a bicontinuous crystalline/amorphous phases was tensile-drawn under various conditions for the structural arrangement of these phases. The prepared film could be drawn below the melting temperature of the polyethylene component, with the highest drawability obtained at 60ｰC. However, the initial bicontinuous structure was gradually destroyed with increasing strain because the drawing temperature was lower than the glass-transition temperature of the polystyrene component. Correspondingly, a necking phenomenon was clearly recognizable when samples were drawn. In contrast, drawing near the melting temperature of the polyethylene component produced less orientation of both the crystalline and amorphous phases, resulting in homogeneous deformation with lower drawing stress. These results indicated that the modification of the lower ductility of the polystyrene component was key to the effective structural arrangement of both phases by tensile drawing. Here, a solvent-swelling technique was applied to improve polystyrene deformability even below its glass-transition temperature. Tensile drawing after such a treatment successfully induced the orientation of both the crystalline and amorphous phases while retaining their initial continuities. A change in the deformation type from necking to homogeneous deformation was also confirmed for the stress-strain behavior