Combining polyethylene and polypropylene: Enhanced performance with PE/iPP multiblock polymers

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Science  24 Feb 2017:
Vol. 355, Issue 6327, pp. 814-816
DOI: 10.1126/science.aah5744

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How to make opposites compatible

Polyethylene (PE) and isotactic polypropylene (iPP) are the two most widely used commodity plastics and thus make up a large fraction of the waste stream. However, the two plastics will not mix together, which limits options for dealing with mixed waste and decreases the value of recycled products. Eagan et al. report the synthesis of multiblock copolymers of iPP and PE by using a selective polymer initiator (see the Perspective by Creton). The high-molecular-weight blocks could be used to reinforce the interface between iPP and PE and allow blending of the two polymers.

Science, this issue p. 814; see also p. 797


Polyethylene (PE) and isotactic polypropylene (iPP) constitute nearly two-thirds of the world’s plastic. Despite their similar hydrocarbon makeup, the polymers are immiscible with one another. Thus, common grades of PE and iPP do not adhere or blend, creating challenges for recycling these materials. We synthesized PE/iPP multiblock copolymers using an isoselective alkene polymerization initiator. These polymers can weld common grades of commercial PE and iPP together, depending on the molecular weights and architecture of the block copolymers. Interfacial compatibilization of phase-separated PE and iPP with tetrablock copolymers enables morphological control, transforming brittle materials into mechanically tough blends.

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