EQUILIBRIUM SHAPES OF MICROPARACRYSTALS IN CHAIN HYDROCARBONS AND AMMONIA CATALYSTS

The linear relationship between the unit cell cross-section ab and the reciprocal of lamellae thickness H, first experimentally observed by Davis et al. for melt- and solution-crystallized linear polyethylene (PE) and paraffins and now also shown to apply for branched materials, can be theoretically derived if one makes use of the presence of microparacrystals. The existence of microparacrystals involves two kinds of novel phenomena: (1) liquid-like lattice distortions which are both limiting the size of the crystallites and sometimes provoking a volume expansion of the lattice; (2) the formation of an equilibrium shape of the microparacrystals. Kinks, branches and thermally-induced rotational distortions give rise to different typical slopes of the linear plots for chain molecules. The slope of the plot for the ammonia catalyst is zero, because no volume increase occurs on the inclusion of FeAl2O4 motives within the lattice. © 1979.