Monoclinic Phase and Competition Between Transformation Modes in the Phase Transition Between Orthorhombic and Triclinic Phases of Crystalline Polyethylene

IA Strelnikov and EA Zubova, MACROMOLECULAR RESEARCH, 29, 851-854 (2021).

DOI: 10.1007/s13233-021-9101-9

We describe the results of the molecular dynamics (MD) simulation(1) of shear-induced martensitic phase transition between the orthorhombic and triclinic phases of crystalline polyethylene (PE). The transition is induced according to two transformation modes observed in experiment on PE single crystals. The kinetics of the transitions proves to depend on the shear rate. Rapid deformation favors the transition directly to the triclinic phase. On the other hand, slow deformation favors the two- stage transition: first to the intermediate monoclinic phase and only then to the triclinic phase. The second way corresponds to the experiment on extended chain PE. We explain this result and analyze the competition between different transformation and plastic deformation modes. Rotations of PE chains around their axes necessary for the transition between the orthorhombic and non-orthorhombic phases are executed by short twist defects diffusing along the chains.

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