TEM observation of latent tracks of heavy ions in semi-crystalline polymers

When high-energetic ions pass a solid they can induce damage in the materia l structure by deposition of a huge amount of energy along their paths. Dep ending upon the kind of material these so-called latent tracks can be etche d by suitable etchants. In this work latent tracks in polymers are investig ated for the first time by transmission electron microscopy (TEM). Bulk pol ymeric material and thin sections of HDPE, LDPE, LLDPE and PP, prepared by cryo-ultramicrotomy were irradiated with high-energetic ions (U, Xe, Zn) an d after chemical staining investigated by TEM. The cross sections of the io n tracks appear as circularly shaped spots in the amorphous regions with di ameters of about 3-8 nm. The mean track diameter increases with the atomic number of the ions. Inside the crystalline lamellae the tracks are elliptic ally shaped with the long axis in parallel orientation to the extended macr omolecules (c-axis). This result indicates breaking and relaxation of macro molecular segments inside the lamellae.