Oriented Recrystallization of Carbon-Coated Pre-oriented Ultrathin Polymer Films

Shouke Yan, and Le Ma

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China

The recrystallization behavior of carbon-coated preoriented polymer thin films was studied by means of transmission electron microscopy combined with electron diffraction and spectroscopy. It was found that vacuum evaporated carbon layer can keep the molecular chain orientation of pre-oriented polymer thin films. This demonstrates the existence of strong fixing effect of vacuum evaporated carbon layers on the surface layer of the polymer films, which prevents the relaxation of surface extended macromolecular stems in the crystals or at least from a complete relaxing during high-temperature melting. Continue reading Oriented Recrystallization of Carbon-Coated Pre-oriented Ultrathin Polymer Films

Surface Nucleation and the Design of Nucleating Agents by Molecular Simulation

Alexander J. Bourque1, C. Rebecca Locker2, and Gregory C. Rutledge1

1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge MA, USA
2ExxonMobil Research and Engineering Company, Annandale, NJ, USA

In most cases of practical interest, nucleation of polymer crystallites is believed to occur heterogeneously, through the action of additives or impurities that serve as nucleation agents, significantly reducing the activation barrier to formation of a new phase [1]. The number and activity of these nucleating agents can alter the resulting morphology of the semicrystalline polymer, for example through polymorph selection, the number and size of spherulites or the orientation of individual lamellae; the properties of the polymer can also be controlled as a consequence. The classical theories of polymer crystal growth are similarly predicated on a surface nucleation mechanism, which may proceed through one or more precursor states. We report the results of molecular simulations that examine the phenomenon of 2-dimensional nucleation on both familiar and foreign surfaces. Continue reading Surface Nucleation and the Design of Nucleating Agents by Molecular Simulation