(433e) Observation of Large Nematic Domain in Suspension of Nano-Plate

Observation of large nematic
domain in suspension of nano-plates

Zhengdong Cheng, Abhijeet
Shinde

Concentration dependent liquid
crystalline phase transitions in aqueous suspensions of plate-like nanoparticles
are of interest to scientists^{1, 2} and engineers³.
From metastable suspension, nematic tactoids nucleate, grow and settle due to
gravity. As the time passes, gravity keeps compressing the nematic tactoids thus
increasing their concentration.  tactoids with different orientations merge and
develop a uniform domain spanned over the entire suspension except the top isotropic
phase. Role of gravity in the formation of the large domain is investigated. It
is also found that growth of the domain is faster in suspensions containing low
aspect ratio (thickness/size) nano-plates. Alignment of nanoplates in the large
domain is studied using polarized optical microscope, circular dichroism and
synchrotron X-ray.

Figure. Cross polarizer
observations of vertical tube containing suspension of nano-plates of same
concentration but at different times. (a) Isotropic (dark) and Nematic
(colorful) phases separation observed in suspension 1 day after its preparation.
Different colors in nematic phase appear due to different orientations of nematic
tactoids. (b) After 70 days, large domain developing near side wall and bottom of
the tube. (c) Large domain with some defects developed in the suspension after 160
days. Directions of polarization in polarizer and analyzer are indicated with lines
?P' and ?A' respectively. Gravity is vertically downwards and is indicated by
arrow ?g'.

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