An unconventional aging mechanism of nanoemulsions

Nanoemulsions were observed in simple dilution experiments, mimicking the flushing step in washing. The used low-energy method takes advantage of the ultra-low interfacial tension of the three-phase region of the underlying microemulsion systems similar to the well-known PIC method but boosted by a simultaneous temperature jump. Following the aging of the nanoemulsions with time-resolved dynamic light scattering, a slow radial growth of order 10 -5 nm/s and, more interestingly, a monomodal and quite narrow distribution of the formed oil droplets was observed, which was also confirmed with SANS measurements. The most astonishing observation was, however, that the aging kinetics of the droplet radius is linear in time (i.e. r ~ t ). This is in contrast to the typical aging mechanisms, Ostwald ripening or coagulation, where the volume is linear with time (i.e. r 3 ~ t ). Preliminary ideas regarding this unexpected and unconventional mechanism are discussed. Graphical abstract Nanoemulsion droplets formed by simultaneous dilution and temperature jump of a microemulsion including ionic and nonionic surfactants during washing. Surprisingly, they show linear radial growth as a function of time in contrast to all known aging mechanisms