Document Type : Review
Authors
1 Iran Polymer and Petrochemical Institute, 14977-13115 Tehran, Iran
2 Arts et Métiers Institute of Technology, CNRS, CNAM, PIMM, HESAM University, 75013, Paris, France
Abstract
Vitrimer chemistry combines network stability with melt reprocessability through dynamic covalent exchange. Extending this to semicrystalline polyolefins is difficult: their backbones are chemically inert, and their morphology adds structural constraints that most vitrimer systems never have to deal with. Polyolefins are among the most demanding substrates for vitrimer design. Reactive functional groups are scarce along the backbone, and crystallinity complicates both the introduction of dynamic chemistry and the interpretation of the resulting rheology. This review examines recent work on polyethylene- and polypropylene-based vitrimers, focusing on reactive processing, molecular architecture, and semicrystalline morphology as coupled factors governing stress relaxation. On this basis, we propose the concept of a pseudo-vitrimeric state: a vitrimer-like rheological response that arises in certain advanced polyethylene of raised temperature resistance (PE-RT) materials from molecular architecture and semicrystalline morphology, without dynamic covalent bond exchange. Long-chain branching and tie-molecule connectivity appear to be the main contributors, retarding relaxation through physical and topological constraints rather than chemical ones. We also outline an experimental framework that combines rheological measurements with structural characterization to distinguish topology-controlled relaxation from relaxation associated with genuine vitrimer chemistry.
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