ANTIPHASE BOUNDARIES AND ORDERING DEFECTS IN SYNDIOTACTIC POLYSTYRENE CRYSTALS

Syndiotactic polystyrene thin films were grown on a hot glycerol surface. Electron diffraction (ED) patterns obtained from monolayer areas show many high-order Bragg reflections suggesting well-developed long-range order as well as streaks of intensity indicating the presence of defects in the crystal lattice. These defects have been characterized in both real and reciprocal spaces by high-resolution electron microscopy (HREM). Optical diffractograms from selected areas (average radius 50 nm) of HREM images show in many cases new reflections in the form of sharp spot(s) and/or short streaks at positions where ED patterns give extended streaks. This additional scattering is shown to arise from small domains that can be imaged by optical filtering and image reconstruction on a laser bench. The domains are elongated and thin (less than 5 nm wide) and are interpreted as a new superstructure sPSs”) by analogy with a recent model (a basic superstructure: sPSs’) proposed for the rest of the crystal. The two superstructures sPSs’ and sPSs” result from ordering between enantiomorphous pairs of molecular clusters, each of them containing three molecules. Periodic arrays of domains of ordering are separated by plane boundaries analogous to antiphase boundaries and give rise to new superlattice reflections. We discuss the generalization of ordering phenomena, which are already well-known in metallic alloys, to a certain class of polymer crystals. © 1990, American Chemical Society. All rights reserved.