Altered Scaling Dynamics in Liquid Crystal Droplet Coalescence: The Role of Surfactants and Marangoni Stresses

Abstract

In the clean-interface limit, the early-stage coalescence of liquid droplets typically follows the standard neck-growth scaling r∝(γR/ρ)1/4t1/2 where inertia dominates. When a surfactant is present, the dynamics can depart substantially from the baseline due to additional interfacial stresses, including Marangoni stresses, interfacial crowding, and liquid-crystal elastic distortion. Here, we quantify the temporal evolution of the contact neck during surfactant-laden coalescence and observe a pronounced retardation of neck expansion. The neck radius is described by a power law, but with a reduced prefactor and apparent exponent relative to the clean limit. We attribute these reductions to the coupled effects of surfactant redistribution, transient Marangoni stresses, interfacial crowding or jamming, and liquid-crystal elasticity, which together resist capillary-driven flow and promote arrested or partially merged coalescence.