Rheological studies on liquid-crystal colloids prepared by dispersing spherical microparticles with homeotropic surface anchoring

ABSTRACT

We report rheological studies on the liquid-crystal colloids prepared by dispersing silica microparticles with homeotropic surface anchoring in 8CB liquid crystal. In nematic colloids, a shear-thickening behaviour is observed in low shear rate region. The apparent yield stress of both the nematic and smectic-A (SmA) phases increases with increasing volume fraction of particles . The critical strain amplitude (, i.e., crossover of and ) in SmA colloids decreases significantly with increasing . The frequency-dependent storage modulus of SmA colloids show a power-law behaviour and the loss modulus exhibits a shallow minimum. The optical rheomicroscopy shows that the nematic colloids form a network structure which are stretched and broken at high shear rate. When the temperature is decreased to SmA phase, the networks collapse showing regions of high-density particles. The variation of storage modulus with indicates that the SmA colloids response is dominated by defects.

Graphical Abstract

KEYWORDS:

• Nematic colloids
• smectic-A colloids
• rheomicroscopy
• soft glass

Acknowledgements

We gratefully acknowledge the support from UPE-II, DST (Project ref.: DST/SJF/PSA-02/2014-2015), CSIR (Project ref.: 03(1207)/12/EMR-II). R.S. acknowledges UGC for BSR fellowship.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

We gratefully acknowledge the support from UPE-II, DST (Project ref.: DST/SJF/PSA-02/2014-2015), CSIR (Project ref.: 03(1207)/12/EMR-II). R.S. acknowledges UGC for BSR fellowship.