Non-fluorinated phosphonium-sulfonate ionic liquids as candidates for thermally demanding applications: thermal stability, viscosity and liquid-state temperature ranges

@article{centenopedrazo2026nonfluorinated,
  title = {{Non-fluorinated phosphonium-sulfonate ionic liquids as candidates for thermally demanding applications: thermal stability, viscosity and liquid-state temperature ranges}},
  author = {A. Centeno-Pedrazo and J. Perez-Arce and B. Iliev and T. J. S. Schubert and S. Lorenz and A. Agrelo-Lestón and M. Haumann and M. Distaso and C. Len and I. Zabala and S. Doppiu and E. J. Garcia-Suarez},
  journal = {RSC Advances},
  year = {2026},
  month = nov,
  doi = {10.1039/d6ra08417f},
  url = {https://doi.org/10.1039/d6ra08417f},
  note = {CC BY 3.0},
}

TY  - JOUR
TI  - Non-fluorinated phosphonium-sulfonate ionic liquids as candidates for thermally demanding applications: thermal stability, viscosity and liquid-state temperature ranges
AU  - A. Centeno-Pedrazo
AU  - J. Perez-Arce
AU  - B. Iliev
AU  - T. J. S. Schubert
AU  - S. Lorenz
AU  - A. Agrelo-Lestón
AU  - M. Haumann
AU  - M. Distaso
AU  - C. Len
AU  - I. Zabala
AU  - S. Doppiu
AU  - E. J. Garcia-Suarez
PY  - 2026
DA  - 2026/11/04
JO  - RSC Advances
DO  - 10.1039/d6ra08417f
UR  - https://doi.org/10.1039/d6ra08417f
AB  - Room-temperature ionic liquids with high thermal stability are attractive candidates for applications requiring operation at elevated temperatures. In this work, a series of non-fluorinated phosphonium-sulfonate ionic liquids was synthesized and systematically characterized to establish structure–property relationships and evaluate their potential as thermally robust fluids. Thermal stability, density, and viscosity were evaluated to determine the influence of cation and anion structure. Under dynamic conditions, all ionic liquids showed encouraging thermal stability, with T5% values of up to 406 °C. Isothermal measurements revealed that four of the seven studied ionic liquids exhibited weight losses equal to 2.6 wt% after 12 h at 300 °C. It has been found that the cation and anion strongly influence thermal stability; in the tributyltetradecylphosphonium ([(C4)3C14P]) cation-based ionic liquids, the presence of an aromatic ring in the anion enhanced stability, highlighting the importance of anion structure. In dodecylbenzenesulfonate ([DBS])-based ionic liquids, the cation bearing the longest alkyl chains exhibited the lowest weight loss under isothermal conditions. Density and viscosity were also strongly dependent on ionic liquid structure and temperature. Longer alkyl chains in the cation led to lower densities, whereas the same trend was observed for the anion within the aromatic subseries. Viscosity decreased strongly with temperature and was mainly controlled by the anion, with [DBS]-based ionic liquids exhibiting the highest values. Within the aromatic-anion subseries, viscosity increased with alkyl chain length, whereas the cation effect was less systematic. Overall, the integration of melting behaviour, isothermal thermal stability, density, viscosity, and viscosity-temperature modelling establishes a structure-guided thermophysical dataset for non-fluorinated phosphonium-sulfonate ionic liquids and defines temperature ranges over which the ILs remain liquid and thermally stable, extending up to 300 °C. For [(C4)3C14P][DBS], an empirical stability model based on isothermal data predicted 1 wt% mass loss after 10 h at 279 °C, providing a quantitative relationship between exposure temperature, time, and degradation. Together, these results highlight the potential of these ILs for applications requiring thermally robust liquids.
SN  - 2046-2069
ER  -