Light scattering quasi-static

In addition to the intrinsic lack of stationarity, many of the fluctuations in the glass relax so slowly that they appear to be static sources of light scattering on the time scale of the data collection. These static contributions will introduce a heterodyne component into the observed relaxation function. If the fraction of the light which is quasi-static exceeds 90%, then the observed relaxation function can be interpreted as a heterodyne case and an analysis can be carried out. However, it is not clear that this limit is ever reached in practice. Only 60% of the light was slowly relaxing at all in polystyrene. If at least 90% of the slowly relaxing part becomes quasi-static the heterodyne case will still apply to the observed part of the relaxation function. For PMMA and PEMA this is unlikely to be the case at any temperature near Tg. 

Micellization of PS-PMA diblock and triblock copolymers in 80 20 dioxane water mixtures was investigated by Qin et al. (1994) using static and quasi-elastic light scattering, differential refractometry, viscomelry, sedimentation... 

It is very well known that the nature of the monolayer partially depends on the strength of interfacial interactions with substrate molecules and that of polymer in-tersegmental interactions. And it is normal to expect that the viscoelastic properties of polymer monolayer are also dependent on these factors. The static and dynamic properties of several different polymer monolayers at the air - water interface have been examined with the surface quasi-elastic Light Scattering technique combined with the static Wilhelmy plate method [101]. 

Two scattering methods, namely time-average (static) Hght scattering and dynamic (quasi-elastic) light scattering (also referred to as photon correlation spectroscopy PCS), will be discussed in the following sections. 

The above observations are in agreement with studies on chain contraction of sodium polymethacrylate (NaPMA) in the presence of Ca2+ and Cu2+ counterions [25]. Static and quasi-elastic light scattering measurements indicate that a PMA chain contracts but does not have a compact spherical structure close to the precipitation threshold. 

De Vos, C., Deriemaeker, L., Finsy, R., Quantitative Assessment of the Conditioning of the Inversion of Quasi-elastic and Static Light Scattering Data for Particle Size Distribution, Langmuir, 1996, 12, 2630-2636. 

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