Micelle formation in tetrahydrofuran-methanol, 1,2-dichloroethane-methanol, tetrahydrofuranwater, and water solutions by PS-PEO diblock copolymers was studied by the fluorescence spectroscopy. For this purpose, a series of PS-PEO copolymers was labeled by the phenanthrene or anthracene groups at the block junctions. The chromophore contents in copolymers were determined by the absorbance spectroscopy using suitable model compounds. When micelles were present, intramicellar nonradiative energy transfer could be observed. For the PS-PEO copolymer (M" = 114 000,93 weight % PEO) we find the onset of micelle formation in water in the range of 10 X 10-3 g/L (9 X -8 M).

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The micellization of three tailor-made triblock copolymers, such as PB 100 -P2VP 100 -PEO 104 , PB 185 -P2VP 108 -PEO 154 , and PB 37 -P2VP 115 -PEO 241 , having similar total molecular weights and constant poly(2-vinylpyridine) (P2VP) sequence lengths, was investigated as a function of pH and sodium dodecyl sulfate (SDS) concentration. At pH 7 the formation of intermicellar aggregates was observed, especially for copolymers of low poly(ethylene oxide) (PEO) content. A pH decrease from 7 to 3 leads to a particle size increase due to the electrostatic repulsion of the protonated P2VP chains. The influence of the PEO sequence length was also observed for zeta potential values. At pH 3, in the absence of SDS, core-shell-corona micelles are formed whereas in the presence of small amount of SDS (degree of neutralization DN 5 0%-50%), a complex is formed between SDS and the protonated P2VP which leads to the shrinkage of the shell and thus to a decrease of the micellar sizes. For higher DN values, the micellar sizes increase due to the formation of large agglomerates and a transition occurs from a monomodal to a bimodal size distribution. Furthermore, it turned out that secondary aggregation, such as intermicellar aggregation, can completely be avoided if the degree of polymerization (DPn) of the water-soluble block is significantly higher than the DPn of the water-insoluble sequence.

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