We study the evolution of the mass of evaporating single microdroplets of sodium dodecyl sulphate (SDS) / diethylene glycol (DEG) mixture. First, we recognise and deconvolute the influence of residual water evaporation [Kolwas et al. Soft Matter 2019;15:1825], which accelerates the composite droplet evaporation, a simple exponential decay of the evaporating droplet surface change rate. This enables us to study the influence of SDS concentration on the composite droplet evaporation. Next, we establish a simple relationship between the average SDS concentration and the droplet evaporation rate to enable the study of the evolution of SDS concentration at the droplet surface. The oscillatory nature of surface SDS concentration indicates cyclic changes in the surface monolayer associated with the cyclic creation of vesicles (micelles) at the surface. The model we developed, allows determination of SDS critical micelles concentration (CMC) in DEG as 60±2 mM.

我们研究了十二烷基硫酸钠（SDS）/二甘醇（DEG）混合物蒸发单个微滴质量的演变。首先，我们认识并消除残留水蒸发的影响[Kolwas等。Soft Matter 2019; 15：1825]，它加速了复合液滴的蒸发，这是蒸发液滴表面变化率的简单指数衰减。这使我们能够研究SDS浓度对复合液滴蒸发的影响。接下来，我们建立平均SDS浓度与液滴蒸发速率之间的简单关系，以研究液滴表面SDS浓度的演变。表面SDS浓度的振荡特性表明表面单层的周期性变化与在表面上形成囊泡（胶束）的循环有关。我们开发的模型可以确定DES中SDS的临界胶束浓度（CMC）为60±2 mM。