Unusual crystallization of polyethylene at melt/atomically flat interface: Lamellar thickening growth under normal pressure

The morphology of polyethylene (PE) crystallized at the melt/atomically flat substrate interface was studied using atomic force microscopy (AFM). Our attention is concentrated on isothermal crystallization of PE on HOPG and MoS2 substrates at high temperatures up to 135 °C. By quenching after different times of crystallization, it was possible to “freeze” the lamellar morphology at various stages of its development at a given supercooling. After detachment of the PE sample from the substrate, individual lamellae (even 150 nm thick) and stacks of the edge-on lamellae after different stages of growth were observed. The similarity of the individual lamellae with those grown from the hexagonal phase under high pressure (characteristic tapered edges), allows to conclude that at the interface, even under normal pressure, the crystallization proceeds according to the mechanism of lamellar thickening growth.