Effect of ionic contaminants on dielectric dispersion and relaxation processes over static permittivity frequency region in neat liquid poly(ethylene glycol)

Finding Infinities in Nanoconfined Geothermal Electrolyte Static Dielectric Properties and Implications on Ion Adsorption/Pairing

“…In the nanoconfined, low-ionic limit where λ exceeds the confinement length, dielectric responses of pure water remain important but are controversial due to the myriad dielectric quantities invoked: ϵ ⊥ ( z ), the corresponding parallel profile ϵ ∥ ( z ), ϵ r , the tensor elements of the dielectric matrix ϵ̅ ⊥ and ϵ̅ ∥ , and what we will call the ion–ion dielectric constant ϵ ii which governs ion–ion interactions. ϵ r can be measured. , ϵ ⊥ ( z ) and ϵ̅ ⊥ are related to capacitance measurements under slit-like nanoconfinement; from this and other experiments, water is inferred to exhibit strongly reduced ϵ̅ ⊥ under confinement. Low ϵ r or ϵ̅ ⊥ values appear empirically correlated with enhanced ion-adsorption/aggregation, but the basis of this approach has been strongly questioned .…”

“…ϵ r can be measured. 7,8 ϵ ⊥ (z) and ϵ ̅ ⊥ are related to capacitance measurements 14 under slit-like nanoconfinement; from this and other 13 experiments, water is inferred to exhibit strongly reduced ϵ ̅ ⊥ under confinement. Low ϵ r or ϵ ̅ ⊥ values appear empirically correlated with enhanced ionadsorption/aggregation, 5 but the basis of this approach has been strongly questioned.…”

“…Dielectric properties in confined liquids are widely acknowledged to govern chemical reactions, ion adsorption at interfaces, contact-ion-pairing, and colloid interactions in electrolytes relevant to physical chemistry, energy storage, and geochemistry. − In the presence of ions, infinities naturally arise in the zero-frequency (ω = 0) limit in unconfined electrolytes (Figure a). This is well-known in low-frequency (ω < 1 kHz) measurements , but its consequences at the atomic length-scale have seldom been examined in modern modeling and experimental efforts, which tend to focus on the MHz to GHz frequency range where water and ionic solutions exhibit a finite plateau in dielectric response. For example, current molecular dynamics (MD) simulations of nano- to microsecond trajectory lengths, by definition, cannot reach frequencies far below 1 kHz, obscuring the divergences in unconfined aqueous media.…”