SELF-ASSEMBLY IN MIXTURES OF POLY(ETHYLENE OXIDE)-GRAFT-POLY(ETHYLENEIMINE) AND ALKYL SULFATES

The complexes formed between the cationic graft copolymer of poly(ethy lene oxide) and poly(ethyleneimine) (PEO-g-PEI) and alkyl sulfate surf actants were studied using potentiometric titration, fluorescence spec troscopy, zeta-potential measurement, dynamic light scattering, and el ectron microscopy. In contrast to the complexes of PEI homopolymer, wh ich phase separate, the PEO-g-PEI complexes are water-soluble over the whole range of compositions of the mixture, including the electroneut ral stoichiometric complexes. These species apparently represent micel le-like aggregates with a hydrophobic core from the surfactant-neutral ized polyions and a hydrophilic corona from the ethylene oxide chains. This is a very different morphology compared to the previously de scr ibed complexes of poly(ethylene oxide)-b-polymethacrylate anions with cationic surfactants, which formed vesicles. The difference in the mor phology is attributed to the difference in the copolymer architecture (branched vs linear, graft vs block copolymer, lengths of chain segmen ts). The unique self-assembly behavior, the simplicity of the preparat ion, and the wide variety of available surfactant components make thes e systems promising in addressing various theoretical and practical pr oblems, particularly, in pharmaceutics.