The effect of magnetic nanoparticles upon the smectic-A to smectic-C* phase transition

ABSTRACT

We report on wide-angle X-ray scattering measurements along the smectic-A to chiral ferroelectric smectic-C* phase transition of the liquid crystal SCE9 and its mixture with maghemite magnetic nanoparticles of typical dimension 20 nm. The temperature profiles of the tilt angle are fitted by an extended mean-field model. Neither pre-transitional order effects nor variations in the SmA layer thickness are observed, indicating a rather negligible influence of these nanoparticles upon the molecular orientation at the smectic-A to smectic-C* phase transition of SCE9. These results are very different from what was observed for smaller CdSe nanoparticles (3.5 nm) where both a dilation of the smectic layers in the SmA phase and a crossover behaviour for the smectic-A to smectic-C* transition away from tricriticality have been observed for analogous concentrations.

GRAPHICAL ABSTRACT

KEYWORDS:

• Magnetic nanoparticles
• X-ray scattering
• smectic liquid crystals

Acknowledgement

The use of the X-ray diffraction facilities of the Center for Crystallography of Macromolecules of N.C.S.R. ‘Demokritos’ is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

G.C. acknowledges the support of the Project PE3-1535 implemented within the framework of the Action ‘Supporting Postdoctoral Researchers’ and G.N. acknowledges the support of THALES Project, both of the Operational Strategic Plan ‘Education and Lifelong Learning,’ co-financed by the European Social Fund and the State of Greece. Z.K. acknowledges the Slovenian Research Agency Project P1-0125.