An investigation on chain mobility in solid state polymer systems

In this paper we have investigated chain mobility in polyethylene below its melting temperature. The investigation techniques like atomic force micros copy (AFM), transmission electron microscopy (TEM), time-resolved small/wid e angle X-ray scattering (SAXS/WAXS), time-resolved longitudinal acoustic m ode (LAM) Raman spectroscopy have been used to follow the chain mobility wi thin individual single crystals and regularly stacked crystals, as a functi on of temperature and time. Our observations on single crystals are that cr ystal thickness increases immediately on heating just above the crystalliza tion temperature. In the regularly stacked polyethylene single crystals whe rever the overlapping of at least two lamellae arises, thickening occurs du ring annealing via a mutual chain rearrangement between the adjacent crysta ls, which leads (ultimately) to a quantum increase, i.e., doubling, of the lamellar thickness. A model has been proposed to explain this quantum incre ase in the lamellar thickness. The fundamental findings have been extended for some applications. (C) 2000 Kluwer Academic Publishers.