The distribution of the unoccupied volume in glassy polymers
The aim of this paper is to present an improved method to describe the unoccupied volume in glassy polymers. The method is able to treat atoms with non-spherical symmetry. The fineness of the raster points scanning the unit cell can be as small as 0.01nm. This method was used to determine the unoccupied volume of molecular dynamic simulations of poly(amide imide) unit cells by probing it with a tracer atom. Since the reachable unoccupied volume strongly depends on the tracer radius, we used tracer radii between 0.03 and 0.17nm. The poly(amide imide)s were used in the present work because they are well characterized, especially there already exist free volume data determined by positron lifetime experiments.
unoccupied volume glassy polymers simulations hole sizes positron annihilation lifetime spectroscopy (pals)