Rayleigh scattering, forced

For data analysis, the following empirical equation is employed  

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Thus, for the investigation of buried polymer interfaces, several techniques with molecular resolution are also available. Recently NMR spin diffusion experiments [92] have also been applied to the analysis of a transition zone in polymer blends or crystals and even the diffusion and mobility of chains within this layer may be analyzed. There are still several other techniques used, such as radioactive tracer detection, forced Rayleigh scattering or fluorescence quenching, which also yield valuable information on specific aspects of buried interfaces. They all depend very critically on sample preparation and quality, and we will discuss this important aspect in the next section. 

The force Rayleigh scattering method was developed by Nagashima s group. Thermal diffusivity can be measured in a contact-free manner within a time interval of 1 ms, with a small temperature rise of 0.1 K and with a small volinne of about 10 mm The sample needs to be colored by an admixture of a dye for suitable absorption of a heating laser beam. The principle is schematically shown in Fig. 32. Two beams of equal intensity divided by means of abeam splitter cross in the sample to create... 

Figure 32. Schematic diagram of the forced Rayleigh scattering method. (Reprinted from Ref 175 with permission of the American Institute of Physics.)...

Kdhler, W and Schdfer, R, Polymer Analysis by Thermal-Diffusion Forced Rayleigh Scattering. Vol. 151, pp. 1-59. 

JA Wesson, H Takezoe, H Yu, SP Chen. Dye diffusion in swollen gels by forced Rayleigh scattering. J Appl Phys 53 6513-6519, 1982. 

TDFRS Thermal diffusion forced Rayleigh scattering... 

Fig. 2.48 Self-diffusion of nearly symmetric diblock copolymers measured using forced Rayleigh scattering (Dalvi et al. 1993). (a) Diffusivities, D, for the lower molecular weight PS-PVP sample, which is disordered at these temperatures, have been scaled down by a factor of 0.48, assumming Rouse dynamics (b) D for the lower molecular weight symmetric PEP-PEE diblock copolymer have been scaled down by a factor of 0.40, assuming reptation dynamics. The solid line indicates a fit of the standard Williams-Landel-Ferry (WLF) temperature dependence to the data for the lower molecular weight sample. Values of M are in g mol1.

Chang, I., F. Fujara, B. Geil, G. Heuberger, T. Mangel, and H. J. Sillescu. 1994. Translational and rotational molecular motion in supercooled liquids studies by NMR and forced Rayleigh scattering. 

Polymer Analysis by Thermal-Diffusion Forced Rayleigh Scattering... 

TDFRS allows for experiments on a micro- to mesoscopic length scale with short subsecond diffusion time constants, which eliminate almost all convection problems. There is no permanent bleaching of the dye as in related forced Rayleigh scattering experiments with photochromic markers [29, 30] and no chemical modification of the polymer. Furthermore, the perturbations are extremely weak, and the solution stays close to thermal equilibrium. 

A TDFRS setup is, in its main components, almost identical to standard forced Rayleigh scattering (FRS) setups as described in many publications [28, 31, 32, 33, 34]. The symmetric arrangement as employed for the more recent work in our group is sketched in Fig. 1. 

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