Dimensional crossover of thermal transport in oligomer aqueous solutions: From three-dimensional to...

We investigated thermal transport in aqueous solutions containing short amphiphilic and purely hydrophilic oligomers using hybrid molecular dynamics and multiparticle collision dynamics simulations. By systematically varying the simulation box length, we observed a dimensional crossover from three-dimensional to quasi-one-dimensional behavior, accompanied by a nonlinear increase in thermal conductivity. This transition was characterized by deviations from theoretical temperature profiles and a prolonged decay of heat flux autocorrelation functions, indicating the emergence of anomalous thermal transport. The addition of oligomers, whether amphiphilic or hydrophilic, promoted the emergence of anomalous behavior compared with pure solvent systems. While the formation of spherical micelles by amphiphilic oligomers increased thermal conductivity, it had minimal influence on the scaling behavior associated with anomalous transport, such as κ∼ξ^{1/3}. These results suggest that geometric anisotropy and the presence of oligomeric solutes are the primary drivers of anomalous thermal transport, whereas self-assembled structures mainly improve thermal transport efficiency. Overall, our findings offer microscopic insights into non-Fourier thermal transport in nanofluids and confined liquid systems and provide a foundation for the rational design of thermally functional materials, where structural organization and transport properties can be tuned synergistically.