Polymer crystal-melt interfaces and nucleation in polyethylene
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.
Cite
@article{arxiv.1009.4245,
title = {Polymer crystal-melt interfaces and nucleation in polyethylene},
author = {Scott T. Milner},
journal= {arXiv preprint arXiv:1009.4245},
year = {2010}
}