Depolarization method

Aoki, H., Kitamura, M. and Ito, S. (2008) Nanosecond dynamics of poly(methyl methacrylate) brushes in solvents studied by fluorescence depolarization method. Macromolecules, 41, 285-287. 

Horinaka, J., Ono, K. and Yamamoto, M. (1995) Local chain dynamics of syndiotactic poly(methyl methacrylate) studied by the fluorescence depolarization method. Polym. J., 27, 429-435. 

Finally, Frisk et al. have proposed a third method, the "depolarization" method, that does not need the assumption of a cylindrical Raman tensor [56]. A randomly oriented sample is again necessary but the depolarization ratio takes the general form... 

The depolarization method is less popular in Tg measurements, firstly due to the difficulty of sample preparation, secondly to the fact that the Maxwell-Wigner-Sillars effect interferes with the depolarization of the dipoles, and thirdly the detrapping of the charges above the transition temperature hinders the detection of the actual depolarization. 

An important advantage of the depolarization technique is that it allows one to measure the molecular ordering, as well as the motional parameters. For this purpose, it is necessary to detect the time dependence of the anisotropy. In the presence of ordering constraints, the r value does not decay to zero, but to some limiting value foo r = (ro — roo)e / c - - poo. The rate of decay defines a rotational correlation time, and Poo is a direct measure of the order parameter through the following relation s = Poo/ o (29). The fluorescence depolarization method works well as long as fluorescence lifetimes, which are typically 10 s, are not too different from the rotation relaxation times to be measured. When the rotational correlation time... 

The measurement of the time-dependent depolarization of the fluorescence from molecules rotating on a time-scale comparable to the fluorescence decay time, enables information to be derived concerning the molecular reorientation motion. A review of these techniques has been published. A method involving an optical delay line has been used to record time-resolved fluorescence depolarization methods using only 1 photodetector, and thus some of the possible instrumental distortions are removed. ... 

This limitation has been overcome by using the resonance depolarization method pioneered by the Novosibirsk group (Derbenev et al, 1978) which requires the measurement of the spin precession frequency of the polarized electron beam. The latter is related to the beam energy by the relation... 

T. Sasaki, M. Yamamoto, and Y. Nishijima. Chain dynamics of poly(methyl methacrylate) in dilute solutions studied by the fluorescence depolarization method. Macromolecules, 21 (1988), 610-616. 

J-i. Horinaka, S. Amano, H. Funada, S. Ito, and M. Yamamoto. Local chain dynamics of poly(oxyethylene) studied by the fluorescence depolarization method. Macromolecules, 31 (1998), 1197-1201. 

PDS, and 6-PDS using the time-resolved fluorescence depolarization method involving two dissimilar probes, 2,5-dimethyl-l,4-dioxo-3,6-diphenylpyr-rolo[3,4-c]pyrrole (DMDPP) and coumarin 6 (C6). The decay of anisotropy for both probes in all the six micelles has been rationalized on the basis of a two-step model consisting of fast-restricted rotation of the probe and slow lateral diffusion of the probe in the micelle that are coupled to the overall rotation of the micelle. On the basis of the assumption that the fast and slow motions are separable, the experimentally obtained slow and fast reorientation times and Xfajt) are related to the time constants for lateral diffusion (xj, wobbling motion (Xw), and rotation of the micelle as a whole (Xm) by the following relationships ... 

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