Rochette, C.N.; Rosenfeldt, S.; Henzler, K.; Polzer, F.; Ballauff, M.; Tong, Q.; Mecking, S.; Drechsler, M.; Narayanan, T.; Harnau, L.: Annealing of Single Lamella Nanoparticles of Polyethylene. Macromolecules 44 (2011), p. 4845-4851
10.1021/ma2003213

Abstract:
We study the change of the size and structure of freely suspended single lamella nanoparticles of polyethylene during thermal annealing in aqueous solutions. Using small-angle X-ray scattering and cryogenic transmission electron microscopy, it is shown that a doubling of the crystalline lamella sandwiched between two amorphous polymer layers is obtained by annealing the nanoparticles at 125 °C. This thickening of the crystalline lamella can be understood in terms of an unlooping of polymer chains within a single nanoparticle. In addition, a variation of the annealing temperature from 90 to 115 °C demonstrates that the inverse of the crystalline lamellar thickness increases linearly with the annealing temperatures leading to a recrystallization line in a Gibbs-Thomson graph. Since the nanoparticles consist of about only eight polymer chains, they can be considered as a ideal candidates for the experimental realization of equilibrium polymer crystals.