Transformation of director configuration upon changing boundary conditions in droplets of nematic liquid crystal

Reversible Switching of Liquid Crystalline Order Permits Synthesis of Homogeneous Populations of Dipolar Patchy Microparticles

“…The preradial configuration involves LC aligned at an acute angle at the droplet surface (e.g., tilted) and a single defect at a pole of the droplet (Figure 1B, middle column). [14, 16, 18, 21-23, 31] We comment that in the absence of the colloids, adsorption of SDS drives a bipolar-to-radial ordering transition (Figure 1A), and thus our observation of the preradial configuration suggests that the presence of the colloids results in an effective “pinning” of a topological defect to the droplet surfaces. [25] Importantly, independent of the positions of the colloids on the surfaces of bipolar droplets prior to addition of SDS (colloids adsorbed at single boojum or colloids adsorbed at each of the two boojums), after addition of SDS, the colloids were observed to locate at the site of the preradial defect (Figure 1B, middle column).…”

“…The bipolar droplet contains LC aligned tangential to the droplet surface and possesses two boojum defects at opposite poles. [14, 16, 21-23, 26] After formation of the bipolar droplets, 1 μm-in-diameter fluorescent PS colloids, at the surfaces of which the LC assumes a tangential anchoring, were adsorbed to the surfaces of the droplets through addition of a 1 % (wt/v) dispersion of the PS colloids, followed by another 30 s of homogenization. Fluorescent PS colloids were used to permit the position of the colloids to be observed by fluorescence (Fluo) microscopy (Figure 1B).…”

“…[14-18] In the study reported in this paper, we demonstrate that reversible manipulation of the surface anchoring of LC droplets decorated with colloids can be used to switch the configurations of LC droplets so as to sweep the colloids into unique locations on the droplet surface for the synthesis of homogeneous populations of patchy microparticles. [12, 14, 22, 23] …”

Director configurations in nematic droplets with tilted surface anchoring

“…Being observed without analyzer the interface is practically invisible where the director is aligned perpendicular to the light polarization because n  np. And vice versa, it is sharply seen where the director is parallel to the polarizer orientation [19][20]. Thus, the comprehensive analysis of the optical textures in both crossed polarizers [1,21] and without analyzer allows determining the director distribution within the droplet.…”

“…The tilted anchoring was realized within liquid matrix in the certain temperature range at the constant concentration of surfactant [7] or for the certain range of surfactant concentration [16]. In PDLC films the resultant director orientation at the interface depends on the droplet size [9], the length of lateral alkyl chains of polymer macromolecules [12], the temperature [17], the variation of curing agent of photo-curable polymer [18], the surfactant content in polymer matrix or LC [19,20].…”