Orientation Overgrowth of Low Molecular Weight Polyethylene during Evaporation

Abstract

Polyethylene (Marlex 6050) was evaporated in vacao on the (OOI) cleavage faces of alkali alide single crystals. By using electron microscopy and electron diffraction method, the moleular orientation of adsorbed 1m on the substrate face and its morphology were investigated; and the. adsorbed film was found to be a low molecular weight polyethylene (M=1000. v5000)(Fig.1). Various shapes of crystals and molecular orientation developed depending upon the vaporating conditions. When the substrate temperature was room temperature and the pressure was P*10-7 Torr, the polyethylene, whose c-axis ran parallel to the substrate face gave rod-like or network crystals oriented in the (110) directions of alkali halide (Figs.3 (a) and 4 (a))and the (110) plane of polyethylene crystal grew in contact with the substrate face. As similar results were obtained with other alkali halide crystals, it is considered that the nucleation is effected by the interaction between the same charge distribution along the (110) directions of he substrate face and the (110) plane of the polyethylene crystal, in-wbich rpolecular chains re contained most densely. When the substrate temperature was higher than 1000C, an llipse-like crystal was obtained. The c-axis oriented still in parallel to the substrate. surf. ace ndr the network structure was maintained inside the crystal (Fig.6 (a)). Above 1500C as he c-axis oriented perpendicularly to the substrate, a disk-like crystal resulted (Fig.8 (a))hich obviously solidified in the eourse of the subsequent cooling.