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Molecular Simulations of Tilted Chain Crystal - Amorphous Interfaces in Polymers

Published online by Cambridge University Press:  10 February 2011

S. Gautam
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
S. Balijepalli
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
G. C. Rutledge
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A. [email protected]
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Abstract

Semi-crystalline polymeric materials exhibit metastable interfaces which must simultaneously feature molecular connectivity through chain bonding and disorder across the interface. To address this, off lattice molecular simulations have been constructed to capture the structure and properties of crystal-amorphous interfaces in polyethylene with freely rotating chains. Monte-Carlo simulations were performed on systems having {001 }, {201} and {502} interfaces (polymer chains tilted to the lamella normal by 0°, 34.4° and 41° respectively.)

Results of the simulations reveal changes in interfacial structure with variation in the chain-tilt angle. The degree of tight folding decreases with increasing tilt, from predominantly [110] loops in the {001} interface to [200] and [310] loops on the other interfaces. The topology shifts towards an increase in loosely folded loops along with longer bridges and tails. The results also compare well with a Gaussian chain length distribution model. The {201} interface exhibits the lowest interfacial energy, in apparent agreement with experimental data.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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