Dynamics of liquid structure relaxation from criticality after a nanosecond laser initiated T-jump in triethylamine-water

Due to its lower critical consolute temperature, we can use a nanosecond laser T-jump to induce spinodal demixing in the triethylamine/water binary mixture. Using a time-resolved Raman probe, we obtained direct molecular level evidence for liquid restructuring in the early stage (<200 ns) of this spinodal decomposition. From these Raman data, we concluded that in this system the early and intermediate stage spinodal dynamics were apparently over within 1 μs. In addition to Raman spectroscopy, we developed a novel shadowgraphic microscopic time-resolved imaging system to get information about morphological changes during demixing, such as phase domain growth rate. In the microsecond time scale, the characteristic scale of length (ξ) of phase domains increased with time following a simple power law ξ ∼ t^0.76(±0.04), while the structure maintained its self-similarity. In this case, the onset of late stage spinodal phase change is several orders of magnitude faster than has been reported for other simple binary mixtures because of the depth of the jump into the two-phase region brought about by our heating pulse.