Nanotech 2011

Connection Between the Crystal and Liquid Crystalline Ordering of iPP and Carbon Nanotube Composites under Melt-Shear

G. Georgiev, M.B. McIntyre, R. Judith, E.A. Gombos, P. Cebe
Assumption College, US

Keywords: multi-walled carbon nanotubes, polymer crystal, smectic phase, anisotropy

Abstract:

We explore the interactions between multi-walled carbon nanotubes (MWCNTs) and the smectic liquid crystal phase of a polymer and the possibility for a similar coupling in this system. Our results indicate that CNTs couple to the smectic phase of isotactic polypropylene (iPP), improve its order upon shearing and the crystals created after the formation of the oriented smectic phase are strongly aligned parallel to the direction of shearing. This result could have impact in microtechnology where aligned polymer films may be useful for the anisotropy of their optical, mechanical, electrical and other properties. We conclude that improved orientation of the crystals in the samples with greater CNTs concentration resulted from increasingly highly oriented liquid crystalline structures formed in the melt during shear. Since the only variable is the CNT concentration and CNTs have been shown to orient under shear stress in the polymers, we conclude that CNTs aid the orientation of the smectic liquid crystal phase by coupling to it. The improved smectic order results in greater crystalline order with increase of the CNTs concentration.
 

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