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Molecular dynamics simulations of side chain liquid crystal polymer molecules in isotropic and liquid-crystalline melts

Stimson, L.M.; Wilson, M.R.

Molecular dynamics simulations of side chain liquid crystal polymer molecules in isotropic and liquid-crystalline melts Thumbnail


Authors

L.M. Stimson



Abstract

A detailed molecular dynamics simulation study is described for a polysiloxane side chain liquid crystal polymer (SCLCP). The simulations use a coarse-grained model composed of a combination of isotropic and anisotropic interaction sites. On cooling from a fully isotropic polymer melt, we see spontaneous microphase separation into polymer-rich and mesogen-rich regions. Upon application of a small aligning potential during cooling, the structures that form on microphase separation anneal to produce a smectic-A phase in which the polymer backbone is largely confined between the smectic layers. Several independent quenches from the melt are described that vary in the strength of the aligning potential and the degree of cooling. In each quench, defects were found where the backbone chains hop from one backbone-rich region to the next by tunneling through the mesogenic layers. As expected, the number of such defects is found to depend strongly on the rate of cooling. In the vicinity of such a defect, the smectic-A structure of the mesogen-rich layers is disrupted to give nematiclike ordering. Additionally, several extensive annealing runs of approximately 40 ns duration have been carried out at the point of microphase separation. During annealing the polymer backbone is seen to be slowly excluded from the mesogenic layers and lie perpendicular to the smectic-A director. These observations agree with previous assumptions about the structure of a SCLCP and with interpretations of x-ray diffraction and small angle neutron scattering data. The flexible alkyl spacers, which link the backbone to the mesogens, are found to form sublayers around the backbone layer.

Journal Article Type Article
Publication Date Jul 1, 2005
Deposit Date May 14, 2007
Publicly Available Date Apr 27, 2011
Journal Journal of Chemical Physics
Print ISSN 0021-9606
Electronic ISSN 1089-7690
Publisher American Institute of Physics
Peer Reviewed Peer Reviewed
Volume 123
Issue 3
DOI https://doi.org/10.1063/1.1948376
Public URL https://durham-repository.worktribe.com/output/1577310

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Copyright Statement
Copyright (2005) American Institute of Physics.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

Stimson, L. M. and Wilson, M. R. (2005) 'Molecular dynamics simulations of side chain liquid crystal polymer molecules in isotropic and liquid-crystalline melts.', Journal of chemical physics., 123 (3). 034908

and may be found at http://dx.doi.org/10.1063/1.1948376






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