TY - JOUR
T1 - Dynamic coupling of a small rigid probe to viscous ortho-terphenyl
AU - Huang, Wei
AU - Richert, Ranko
PY - 2010/12/7
Y1 - 2010/12/7
N2 - We have measured the dielectric relaxation of 2,2,6,6-tetramethyl- piperidine-1-oxyl (TEMPO) as a rotational probe in supercooled ortho-terphenyl (OTP). Due to the significant dipole moment of TEMPO compared with OTP, its contribution to the loss spectra can be identified already at moderate concentrations. For time scales ranging from 10 s to 1 s, it is found that the tumbling mode of TEMPO is a true replica of the structural relaxation of OTP regarding average time constant, relaxation time dispersion, and the temperature dependence. While the present dielectric results are consistent with a decoupling of a spinning mode (about the nitroxyl dipole axis) of TEMPO from viscosity, they do not agree with the strong decoupling of the tumbling mode derived from electron spin resonance experiments.
AB - We have measured the dielectric relaxation of 2,2,6,6-tetramethyl- piperidine-1-oxyl (TEMPO) as a rotational probe in supercooled ortho-terphenyl (OTP). Due to the significant dipole moment of TEMPO compared with OTP, its contribution to the loss spectra can be identified already at moderate concentrations. For time scales ranging from 10 s to 1 s, it is found that the tumbling mode of TEMPO is a true replica of the structural relaxation of OTP regarding average time constant, relaxation time dispersion, and the temperature dependence. While the present dielectric results are consistent with a decoupling of a spinning mode (about the nitroxyl dipole axis) of TEMPO from viscosity, they do not agree with the strong decoupling of the tumbling mode derived from electron spin resonance experiments.
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U2 - 10.1063/1.3506405
DO - 10.1063/1.3506405
M3 - Article
C2 - 21142302
AN - SCOPUS:79251474910
SN - 0021-9606
VL - 133
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 21
M1 - 214501
ER -