High electric fields elucidate the hydrogen-bonded structures in 1-phenyl-1-propanol

High electric fields are applied to illuminate the role of hydrogen bonding in the dielectric relaxation of 1-phenyl-1-propanol (1P1P). Unlike many other monohydroxy alcohols, 1P1P is not associated with a strong distinct Debye loss peak, which would indicate chain-like hydrogen-bonded structures. We exploit the feature that a high field induced enhancement of the dielectric constant indicates a shift of the thermodynamic equilibrium towards more polar (e.g., chain-like) structures. This so-called ‘chemical effect’ rests on a field-induced lowering of the free energy of the more polar species, thus shifting the equilibrium towards a higher dielectric constant. We demonstrate that an external electrical field of E_B = 245 kV cm⁻¹ increases the amplitude of the Debye peak, whereas that of the remaining loss profile remains constant. This indicates the coexistence of chain-like and less polar structures in supercooled 1P1P and helps to discriminate the Debye process from the signature of the primary structural relaxation.