Time-resolved fluorescence depolarization is applied to investigate the association of sodium n-dodecyl sulfate (SDS) micelles with poly(N-isopropylacrylamide) in aqueous solutions using an amphiphilic fluorescent probe (3-perylenedodecanoic acid) which is incorporated into the SDS micelles. First, the effect of the surfactant concentration was measured:  in the presence of the polymer, above the critical aggregation concentration (CAC) of SDS, the rotational relaxation of the probe exhibits a slow and a fast component. The relaxation time of the fast component is the same as in a polymer-free solution above the CMC of SDS where, however, only one component is observed. The slower relaxation time is attributed to polymer-bound micelles which incorporate polymer segments into their core. Second, the effect of the temperature induced coil−globule transition is investigated:  in the course of the transition the rotational motion slows down almost 10-fold, indicating that the probe remains firmly associated with the polymer even in its dense globular state.

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The scattering properties of gelatin containing WiO microemulsions near the sol-gel transition are discussed. The fractal dimension of the aggregates and network is found to be 1.65 k 0.05 for length scales larger than the radius of gyration of the gelatin containing aqueous microemulsion droplets (nanogels, R , = 30 nm from light scattering). At smaller length scales (SAX-scattering) the interface of the droplets appears relatively rough with a surface fractal dimension D, = 3.0. The results agree with the concept of a network being built up by polymers cross-linking the nanogels.

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