Enhanced Diffusion at Intermediate Stereochemical Composition in Polypropylene by Dynamical Monte Carlo

Autor:	Ernst D. von Meerwall, Wayne L. Mattice, Numan Waheed
Rok vydání:	2007
Předmět:	Polypropylene Polymers and Plastics Chemistry Diffusion Organic Chemistry Monte Carlo method Thermodynamics Composition (combinatorics) Inorganic Chemistry chemistry.chemical_compound Pair correlation Tacticity Polymer chemistry Materials Chemistry Cluster (physics)
Zdroj:	Macromolecules. 40:1504-1511
ISSN:	1520-5835 0024-9297
DOI:	10.1021/ma062285r
Popis:	We conduct a comprehensive study of the effect of stereochemistry on the diffusion of isotactic, atactic, and syndiotactic polypropylene (PP), with dynamical Monte Carlo. We simulate realistic two-bead Monte Carlo moves on a stereochemistry-dependent, coarse-grained model of PP based on the rotational isomeric state (RIS) model and repulsive Lennard-Jones interactions. We find that isotactic PP (iPP) diffuses faster than syndiotactic PP (sPP) as expected, but a maximum in the diffusion rate at an intermediate stereochemical composition (aPP) is also found. To determine the origin of this effect, we compare pair correlation functions of the slowest-moving beads to those of all beads, identifying conformations that limit mobility. We find a few small, long-lived clusters with chain conformations reminiscent of those in crystals in iPP and sPP; although slow-moving beads also cluster in aPP, they are short-lived with no dominant conformations. We look at the effects of local stereochemistry through Monte Car...
Databáze:	OpenAIRE
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