Rheology and morphology of smectic liquid crystal/polymer blends

Jun Yonezawa, Stephen M. Martin, Christopher W. Macosko, Michael Ward

Research output: Contribution to journalArticle

Abstract

Polymers are often blended with additives (e.g., polymers, clays) to produce composite materials having desirable physical properties that reflect synergy between the blend constituents. Though polymer blends with small-molecule nematic liquid crystal phases have been investigated (primarily for displays), related materials containing small-molecule smectic phases have not been reported. Guanidinium alkylbenzenesulfonates (GCnBS, where n is the number of carbons in the alkyl chain), which form stable smectic phases at elevated temperatures because of a robust two-dimensional hydrogen-bonding network of guanidinium ions and sulfonate moieties, were melt-blended with various polymers. Rheological characterization of the blends reveals a yielding behavior, characteristic of the pure GCnBS smectic phases, which becomes more pronounced with increasing GCnBS concentration. Two micro-structures-one a continuous polymer phase embedded with GCnBS droplets and the other a continuous GCnBS phase with a discontinuous polymer phase-are observed, the latter at GCnBS concentrations as low as 2 wt %. The tendency of the blends to form a microstructure in which GCnBS is continuous requires the existence of a smectic phase (observed only for n ≥ 7) and is dependent on alkyl chain length and GCnBS concentration. Injection of molten blends containing smectic phases into a rectangular mold resulted in stratification of the rectangular composite plaque due to the formation of large two-dimensional crystalline lamellae upon cooling of the GCnBS smectic phase dispersed in the blend. This stratification, which can be attributed to large extensional stresses experienced by the blend during molding, depends on alkyl chain length, GCnBS concentration, and the magnitude of the stresses exerted on the molten blend. These results illustrate that smectic phases can promote unusual microstructures in polymer blends at very low concentrations, which may be useful in certain commercial applications.

Original languageEnglish (US)
Pages (from-to)6424-6432
Number of pages9
JournalMacromolecules
Volume37
Issue number17
DOIs
StatePublished - Aug 24 2004

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Smectic liquid crystals
Liquid crystal polymers
Polymer blends
Rheology
Polymers
Guanidine
Chain length
Microstructure
Molten materials
Molecules
Nematic liquid crystals
Composite materials
Molding
Hydrogen bonds
Clay
Carbon
Physical properties
Display devices
liquid crystal polymer
Ions

ASJC Scopus subject areas

  • Materials Chemistry

Cite this

Rheology and morphology of smectic liquid crystal/polymer blends. / Yonezawa, Jun; Martin, Stephen M.; Macosko, Christopher W.; Ward, Michael.

In: Macromolecules, Vol. 37, No. 17, 24.08.2004, p. 6424-6432.

Research output: Contribution to journalArticle

Yonezawa, J, Martin, SM, Macosko, CW & Ward, M 2004, 'Rheology and morphology of smectic liquid crystal/polymer blends', Macromolecules, vol. 37, no. 17, pp. 6424-6432. https://doi.org/10.1021/ma0493729
Yonezawa, Jun ; Martin, Stephen M. ; Macosko, Christopher W. ; Ward, Michael. / Rheology and morphology of smectic liquid crystal/polymer blends. In: Macromolecules. 2004 ; Vol. 37, No. 17. pp. 6424-6432.
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