Dynamic light scattering micellar system

There continues to be extensive interest in latexes and micellar systems. The structure of acrylic latex particles has been investigated by non-radiative energy transfer by labelling the co-monomers with fluorescent acceptor-donor systems. Phase separations could also be measured in this way. Excimer fluorescence has been used to measure the critical micelle temperature in diblock copolymers of polystyrene with ethylene-propylene and the results agree well with dynamic light scattering measurements. Fluorescence anisotropy has been used to measure adsorption isotherms of labelled polymers to silica as well as segmental relaxation processes in solutions of acrylic polymers. In the latter case unusual interactions were indicated between the polymers and chlorinated hydrocarbon solvents. Fluorescence analysis of hydrophobically modifled cellulose have shown the operation of slow dynamic processes while fluorescence... 

Results from dynamic light scattering (DLS) titrations. Atomic Force Microscopy (AFM), surface force measurements and rheology will be used to illustrate how differences in kinetics show up in experiments on colloidal micellar systems. 

One of the recent topics in studies of dynamic light scattering is finding the slow mode for polymeric systems. First observation of the slow mode was reported on the semidilute solutions of polystyrene in theta solvent by Adam and Delsanti [1]. Since then, the slow mode has been observed in several solutions in theta or poor solvents where polymer chains tend to associate with each other weakly [2-5]. Besides them, in recent years, the slow relaxation mode was also observed in the thread-like micellar system formed by the cationic surfactant in aqueous solutions [6]. If weak interaction between chains... 

In Section 20.2 the use of three spectroscopic methods has been exemplified for obtaining information on diffusion coefficients in surfactant systems. Regarding the micellar phases both, NMR self-diffusion measurements and FRS, have been successfully used to monitor changes in the micellar diffusion coefficients resulting from size and shape changes. This information complements the results from static and dynamic light scattering experiments in a most valuable manner. 

Experiments have been performed on different systems where attractive interactions could be induced, such as colloid-polymer mixtures [39,66] or micellar systems [67]. Figure 7.23 shows the correlation functions of these systems obtained from dynamic light scattering, confirming the existence of the high-order singularity in the region where MCT predicts it. 

Concurrent to the development of theoretical models to describe planar and curved polymer bmsh systems a wide range of experimental techniques (such as neutron scattering, evanescent static and dynamic light scattering or fluorescence, and rheological techniques) were applied to elucidate the effect of bmsh architecture on the stmcture and dynamic properties of polymer bmsh systems. Similar to the development of theoretical models, early experimental studies were focused on planar polymer bmsh architectures as well as on star polymer and block copolymer micellar systems. Only recently, experimental studies were extended to particle bmsh systems. 

Despite the fact that here one has the typical composition of a microemulsion, i.e., surfactant-water-oil, one does not find a low viscosity microemulsion but instead a highly viscous system. The addition of water results in the formation of flexible cylindrical reverse micelles that form a transient network of entangled micelles and has been characterized by means of dynamic shear viscosity measurements [73,74]. Light scattering experiments on systems with cyclohexane as the oil have demonstrated that a water-induced micellar growth occurs and that these systems may be described analogously to semidilute polymer solutions [75-77]. 

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