Investigation of molecular orientation and conformational change upon drawing for various ethylene/1‐butene copolymers by IR spectroscopy

Infrared spectroscopy was used to investigate the molecular orientation and the conformational change upon drawing for various ethylene/1‐butene copolymers in a wide range of crystallinity (0 ≤ X c ≤ 85% ). The degree of crystalline orientation at constant draw ratio decreases with increasing crystallinity. The orientation function for the amorphous CH 2 sequence in the trans conformation, f (am) , was calculated assuming additivity for the orientation functions of the trans bands. f (am) increases with drawing in a characteristical way for the different materials and reaches a value higher than that of the amorphous gauche bands. Furthermore, it was found that f (am) is strongly dependent on crystallinity. The relative concentration of the amorphous CH 2 sequences in the trans conformation increases at the expense of that of the gauche sequences. The transformation from gauche to trans in the amorphous phase occurs simultaneously with the orientation of the amorphous CH 2 sequences.