Polymer crystal-melt interfaces and nucleation in polyethylene

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Abstract

Kinetic barriers cause polymers to crystallize incompletely, into nanoscale lamellae interleaved with amorphous regions. As a result, crystalline polymers are full of crystal-melt interfaces, which dominate their physical properties. The longstanding theoretical challenge to understand these interfaces has new relevance, because of accumulating evidence that polymer crystals often nucleate via a metastable, partially ordered "rotator" phase. To test this idea requires a theory of the bulk and interfacial free energies of the critical nucleus. We present a new approach to the crystal-melt interface, which represents the amorphous region as a grafted brush of loops in a self-consistent pressure field. We combine this theory with estimates of bulk free energy differences, to calculate nucleation barriers and rates via rotator versus crystal nuclei for polyethylene. We find rotator-phase nucleation is indeed favored throughout the temperature range where nucleation is observed. Our methods can be extended to other polymers.

Original languageEnglish (US)
Pages (from-to)2909-2917
Number of pages9
JournalSoft matter
Volume7
Issue number6
DOIs
StatePublished - Mar 21 2011

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics

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