Straining Soft Colloids in Aqueous Nematic Liquid Crystals

Liquid crystals (LCs), due to their long-range molecular ordering, are anisotropic, elastic fluids. This presentation will report that elastic stresses imparted by nematic LCs can dynamically shape soft colloids and tune their physical properties. Specifically, we use giant unilamellar vesicles (GUVs) as soft colloids, and explore the interplay of mechanical strain when the GUVs are confined within aqueous chromonic LC phases. Accompanying thermal quenching from isotropic to LC phases, we observe the elasticity of the LC phases to transform initially spherical GUVs (diameters 2-50 µm) into two distinct populations of GUVs with spindle-like shapes and aspect ratios as large as 10. Large GUVs are strained to a small extent (R/r < 1.54, where R and r are the major and minor radii, respectively) consistent with an LC elasticity-induced expansion of lipid membrane surface area of up to 3% and conservation of the internal GUV volume. Small GUVs, in contrast, form highly elongated spindles (1.54 < R/r < 10) that arise from an efflux of LC from the GUVs during the shape transformation, consistent with LC-induced straining of the membrane leading to transient membrane pore formation. A thermodynamic analysis of both populations of GUVs reveals the final shapes adopted by these soft colloids are dominated by a competition between the LC elasticity and an energy (~0.01 mN/m) associated with the GUV-LC interface. Overall, these results provide new insight into the coupling of strain in soft materials and suggest new designs of LC-based responsive and reconfigurable colloidal dispersions.