Crystallization and melting simulations of oligomeric α1 isotactic polypropylene

Romanos, NA; Theodorou, DN

dc.contributor.author	Romanos, NA	en
dc.contributor.author	Theodorou, DN	en
dc.date.accessioned	2014-03-01T01:33:06Z
dc.date.available	2014-03-01T01:33:06Z
dc.date.issued	2010	en
dc.identifier.issn	00249297	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20319
dc.subject	Polypropylene	en
dc.subject.other	1-forms	en
dc.subject.other	Crystal configuration	en
dc.subject.other	Density change	en
dc.subject.other	Diffraction data	en
dc.subject.other	Equilibrium melting temperature	en
dc.subject.other	First order transitions	en
dc.subject.other	Flexible force	en
dc.subject.other	Force fields	en
dc.subject.other	Gibbs-Duhem integration	en
dc.subject.other	Glass temperatures	en
dc.subject.other	Helical conformation	en
dc.subject.other	Isobaric condition	en
dc.subject.other	Isotactic poly(propylene) (iPP)	en
dc.subject.other	Isotactic polypropylene	en
dc.subject.other	Isothermal-isobaric simulation	en
dc.subject.other	Melt configurations	en
dc.subject.other	Melt state	en
dc.subject.other	Melting simulations	en
dc.subject.other	Molecular dynamics simulations	en
dc.subject.other	Monoclinic symmetry	en
dc.subject.other	Solid-liquid coexistence	en
dc.subject.other	Sub-domains	en
dc.subject.other	United atoms	en
dc.subject.other	Crystallization	en
dc.subject.other	Grain boundaries	en
dc.subject.other	Liquids	en
dc.subject.other	Melting	en
dc.subject.other	Molecular dynamics	en
dc.subject.other	Polypropylenes	en
dc.subject.other	Thermoplastics	en
dc.subject.other	Crystal symmetry	en
dc.title	Crystallization and melting simulations of oligomeric α1 isotactic polypropylene	en
heal.type	journalArticle	en
heal.identifier.primary	10.1021/ma100677f	en
heal.identifier.secondary	http://dx.doi.org/10.1021/ma100677f	en
heal.publicationDate	2010	en
heal.abstract	The crystallization and melting of the α1 form of isotactic polypropylene (iPP) was studied with molecular dynamics (MD) simulations, using a fully flexible force field representing the C and H atoms atomistically and the CH3 groups as united atoms. Initially, a model crystal lattice of iPP of infinite molar mass was generated from experimental diffraction data, adding the pendant and geminal hydrogens. Next, crystal configurations of finite molar mass were created from this initial model lattice, and it was verified that the force field could preserve the crystal structure, keeping intact the monoclinic symmetry of the crystal. The generated configurations were heated under isobaric conditions, until a first-order transition into the melt state took place. The density change upon melting and the enthalpy of melting were estimated as differences between well-equilibrated ensembles of crystal and melt configurations. In order to calculate the equilibrium melting temperature Tm, composite (sandwich) configurations consisting of both melt and crystal subdomains in contact with each other were generated and subjected to a series of isothermal - isobaric simulations at a variety of temperatures. Tm was determined as that temperature where none of the phases in the sandwich grew at the expense of the other. As proximity to the glass temperature Tg made the dynamics of crystal growth very sluggish, a constraining potential inducing helical conformations along the chains was introduced to accelerate crystallization. Using a novel Gibbs - Duhem integration scheme that utilizes data from both sandwich and single-phase solid and liquid simulations, results for equilibrium solid - liquid coexistence were extrapolated to zero constraining potential. An accurate estimate of Tm was thereby obtained. © 2010 American Chemical Society.	en
heal.journalName	Macromolecules	en
dc.identifier.doi	10.1021/ma100677f	en
dc.identifier.volume	43	en
dc.identifier.issue	12	en
dc.identifier.spage	5455	en
dc.identifier.epage	5469	en