Memory effect of the molecular topology of lamellar polyethylene on the strain-induced fibrillar structure

The fibrillar structure that develops upon drawing of semi-crystalline polymers has been investigated at room temperature by means of in situ SAXS for a series of ethylene copolymers crystallized through various thermal treatments. The long period of the microfibrils for any given material proved to be only dependent on the experimental conditions of the drawing. This suggested the occurrence of a destruction and reconstruction of the semi-crystalline structure via fragmentation accompanied with melting–recrystallization. However, the diameter of the microfibrils proved to keep the memory of the lamellar microstructure via a correlation with the content of interphase at the crystal-amorphous boundary. A physical explanation is proposed for these apparently antagonist findings. The memory of the lamellar semi-crystalline microstructure is completely erased in the microfibrils owing to the melting–recrystallization process. In contrast, the diameter of the fibrils keeps the memory of the chain topology to which a major role is ascribed in the strain-induced fragmentation of the crystalline lamellae.