Morphology of semicrystalline block copolymers: polyethylene-b-atactic-polypropylene

Transmission electron microscopy (TEM) and electron diffraction (ED) are us ed to study the morphology of a semicrystalline polyolefin diblock copolyme r polyethylene-b-atactic-polypropylene (PE-b-aPP) and its blend with polyet hylene homopolymer. By using RuCl3/NaClO as the staining agent, both the co ntrast between amorphous PP and amorphous PE regions and the contrast betwe en amorphous PE regions and crystalline PE regions can be obtained. As a re sult, both the larger lamellar structures due to microphase separation and the smaller crystalline PE lamellae can be resolved on TEM micrographs. Ele ctron diffraction coupled with TEM imaging is used to elucidate the orienta tion of PE crystallites with respect to the interfaces of the microphase se parated block copolymer lamellar domains. Fast quenching from a microphase separated melt-state was found to result in confinement of PE crystallizati on within the microphase separated PE domains of the block copolymer morpho logy. The orientation of the PE crystallites thus formed was found to be ra ndom. (C) 2001 Elsevier Science Ltd. All rights reserved.