Abstract

Soft supramolecular materials often exhibit hierarchical organization accompanied by collective fluctuations over broad spatial and temporal scales. In this study, we investigate how solvent-dependent self-assembly governs acoustic energy dissipation in phenol–AOT organogels [1]. Fig. 1 illustrates the present concept schematically.

Phenol and bis(2-ethylhexyl) sulfosuccinate (AOT) spontaneously form organogels in several organic solvents through hydrogen bonding and solvophobic association. We prepare organogels using cyclohexane, hexane, m-xylene, and 2,2,4-trimethylpentane. Scanning electron microscopy (SEM) reveals solvent-dependent interconnected domains comprising lamellar and sheet-like aggregated structures on the micrometer scale. Cyclohexane- and hexane-based systems generate comparatively heterogeneous porous structures, whereas m-xylene produces smoother and more continuous domains.

We measure sound attenuation under Z- and A-weighting conditions in the audible-frequency region. The results suggest that mesoscale organization governs acoustic dissipation in these soft materials. Because acoustic wavelengths greatly exceed the characteristic pore dimensions observed by SEM, direct scattering from individual pores likely plays only a minor role. Instead, collective viscoelastic relaxation and dynamic structural rearrangements within interconnected domains efficiently dissipate acoustic energy. Agarose hydrogels possessing nanoscale network structures also exhibit attenuation profiles similar to those of the organogels, suggesting that hierarchical organization itself plays an essential role in acoustic dissipation in soft matter systems.

Fig. 1. Schematic concept of organogel structures applied to sound attenuation.

References

[1] KN. et al., Phys. Chem. Chem. Phys. 25 (2023) 2776–2780.