Micelle Characterisation Experimental Techniques

Several experimental techniques are available for the investigation of miceUar systems, capable of elucidating different aspects of the miceUisation process, as well as the micellar structure and morphology. In a first approach, these techniques can be categorised in three subclasses microscopy, scattering and spectroscopic techniques. Extensive reviews on the various experimental methods suitable for block copolymer micelle characterisation have been provided [6-8]. Therefore, in this section, our aim is to briefly outline the different methods used and the information they provide, along with some of their main advantages and limitations [1,2,71]. 

This subcategory includes static and dynamic light scattering (SLS and DLS), along with small-angle X-ray and neutron scattering (SAXS and SANS) techniques. 

Additional information on potential alterations of chain conformations or core/ corona interface due to micellisation can also be gained. Similarly, the application of NMR spectroscopy for the study of chain dynamics in micellar systems is based mainly on the fact that block copolymer segment mobility is directly correlated to the intensity of respective NMR spectrum peaks. Thus, when the core of the micelles is formed and the mobility of the insoluble blocks is significantly reduced, the intensity of the corresponding NMR peaks is reduced accordingly. 

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The kinetics of formation and disintegration of micelles has been studied for about thirty years [106-130] mainly by means of special experimental methods, which have been proposed for investigation of fast chemical reaction in liquids [131]. Most of the experimental methods for micellar solutions study the relaxation of small perturbations of the aggregation equilibrium in the system. Small perturbations of the micellar concentration can be generated by either fast mixing of two solutions when one of them does not contain micelles (method of stopped flow [112]), or by a sudden shift of the equilibrium by instantaneous changes of the temperature (temperature jump method [108, 124, 129, 130]) or pressure (pressure jump method [1, 107, 116, 122, 126]). The shift of the equilibrium can be induced also by periodic compressions or expansions of a liquid element caused by ultrasound (methods of ultrasound spectrometry [109-111, 121, 125, 127]). All experimental techniques can be described by the term relaxation spectrometry [132] and are characterised by small deviations from equilibrium. Therefore, linearised equations can be used to describe various processes in the system. 

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