화학공학소재연구정보센터
Langmuir, Vol.22, No.5, 2365-2370, 2006
Spontaneous size selection in cholesteric and nematic emulsions
We study the spontaneous size selection in lyotropic cholesteric (W/O) and thermotropic nernatic (O/W) liquid crystal emulsions. The droplet sizes have been characterized by dynamic light scattering, which indicates a narrow monomodal distribution of droplets achieved spontaneously even without emulsion filtration. Anchoring of the director, provided by the chosen surfactant on the interface, may generate a topological defect inside the droplet. Below the critical radius R* = K/W, determined by the ratio of Frank elastic and the surface anchoring constants, the effective anchoring strength is weak and droplets are not topologically charged: this allows them to coalesce freely, depleting the size distribution in this range. Large droplets possess a topological charge of +1 and present a high elastic energy barrier for pair coalescence, the resulting size distribution is skewed. with R > R*, and effectively frozen.