  Hypothesis: Surfactant-free microemulsion (SFME), an emerging phenomenology
that occurs in the monophasic zone of a broad category of ternary mixtures
'hydrophobe/hydrotrope/water', has attracted extensive interests due to their
unique physicochemical properties. The potential of this kind of ternary fluid
for solubilization and drug delivery make them promising candidates in many
industrial scenarios. Experiments: Here the thermodynamic behavior of these
multiscale nanodomains formed in the ternary trans-anethol/ethanol/water system
over a wide range of temperatures is explored. The macroscopic physical
properties of the ternary solutions are characterized, with revealing the
temperature dependence of refractive index and dynamic viscosity. Findings:
With increasing temperature, the ternary system shows extended areas in the
monophasic zone. We demonstrate that the phase behavior and the multiscale
nanodomains formed in the monophasic zone can be precisely and reversibly tuned
by altering the temperature. Increasing temperature can destroy the stability
of the multiscale nanodomains in equilibrium, with an exponential decay in the
scattering light intensity. Nevertheless, molecular-scale aggregates and
mesoscopic droplets exhibit significantly different response behaviors to
temperature stimuli. The temperature-sensitive nature of the ternary SFME
system provides a crucial step forward exploring and industrializing its
stability.
