Aggregation numbers and microstructure characterization of self-assembled aggregates of poly(ethylene oxide) surfactants and related block-copolymers, studied by spectroscopic methods

This review presents typical examples of micellar size measurements and str uctural characterization of self-assembled systems as determined with spect roscopic methods, selected from our representative results accumulated in r ecent years of systematic studies. The choice of examples has aimed at emph asizing the potentiality of the methods used in the study of poly(ethylene oxide) (PEO) surfactants. By using the time-resolved fluorescence quenching method aggregation numbers have been determined for direct and reverse mic elles as well as for micelle-like clusters formed in (bio)polymer-surfactan t solutions. By using specific spectral parameters of a variety of properly chosen molecular probes [fluorescence, UV-VIS and electron spin resonance (ESR) spin probes], problems such as hydration degree and profile of the PE O chains, local viscosity, ordering and packing of surfactant chains have b een addressed. The intention was to correlate results obtained from differe nt spectroscopic methods and to refer all polarity data to a common scale, such as Kosower's polarity factor. (C) 2001 Elsevier Science B.V. All right s reserved.