FULL PAPER Interactions between Chromophore-Labelled Ammonium Surfactants and Hydrophobically Modified Polyelectrolytes Armanda C. Nieuwkerk, [a] Ellen J. M. van Kan, [a] Arie Koudijs, [a] Antonius T. M. Marcelis, [a] and Ernst J. R. Sudhölter* [a] Keywords: UV spectroscopy / Poly(maleic acid-co-alkyl vinyl ether)s / Azobenzene / (Cyanobiphenylyl)oxy / Cooperative binding The interaction of poly(maleic acid- co-alkyl vinyl ether)s and binding. This is attributed to the formation of microdomains by the polyelectrolytes themselves. For these systems the poly(sulfonylethyl maleic acid monoamide- co-alkyl vinyl ether)s with and without (cyanobiphenylyl)oxy chromo- formation of mixed micelles is assumed. The compactness of the microdomains of the maleic acid copolymers is phores with N -[ω-(substituted azobenzoxy)alkyl]- N ,N - dimethyl- N -hydroxyethylammonium bromide surfactants influenced by the pH and binding with surfactants is also influenced by pH. The sulfonylethyl maleic acid monoamide has been studied by UV spectroscopy. The azobenzene unit is functionalized at the 4'-position with a cyano or fluoro copolymers show no pH dependence in binding above neutral pH. For these polyelectrolytes the cooperativity also substituent and is connected to the surfactant headgroup via a decyl or dodecyl spacer. Upon addition of surfactants to becomes less with a longer spacer between backbone and chromophore. Upon elongation of the surfactant spacer or poly(maleic acid- co-butyl vinyl ether) the absorption maxima (λ max ) of the azobenzene chromophores immediately show changing the end group from a cyano to the more hydrophobic fluoro substituent a lower λ max is observed for their maximum blue shift. This indicates cooperative binding of surfactant to this polymer, and the formation of micelle- the chromophores upon initial binding to the polyelectrolytes indicating more cooperative binding. When surfactants and like aggregates surrounded by polyelectrolyte is assumed. Upon addition of the surfactants to the other polyelectrolytes polyelectrolytes are both labelled with chromophores, binding proceeds noncooperatively and the formation of λ max values of the azobenzoxy chromophores gradually shift to lower values indicating a lower cooperativity of surfactant mixed micelles is assumed. Spectroscopic techniques like UV/Vis and fluorescence and surfactants result from the aggregation or deaggre- gation of the chromophores. spectroscopy are often used to investigate the interactions between polymers and surfactants. [1-5] Spectral changes It can be expected that changes in both the hydro- phobicity and hydrophilicity of the polyelectrolytes and the which occur upon the binding of surfactants to polymers, like shifts in absorption maxima, peak widths and peak surfactants will influence their interaction. In this paper a UV-spectroscopy study is presented on the interaction of asymmetry, result from a change in polarity of the micro- environment (solvatochromic shift) or from exciton forma- poly(maleic acid-co-alkyl vinyl ether)s Cn acid and I-n, and the more hydrophilic poly(sulfonylethylmaleic acid tion. Most polymers and surfactants do not possess internal monoamide-co-alkyl vinyl ether)s Cn sulfonate and II-n (Scheme 1) with ammonium surfactants that have a N,N - probes to monitor spectroscopic changes, therefore external probes have to be added, like e.g. pyrene in fluorescence dimethyl-N -hydroxyethylammonium head group and fluoro- or cyanoazobenzene chromophoric units connected studies. [2] Another method which is often applied is the modification of polymers or surfactants by covalent bond- via a decyl or dodecyl spacer. The sulfonylethyl group con- taining polyelectrolytes Cn sulfonate and II-n are better ing of small amounts of probe molecules. A disadvantage of both systems is that the presence of even a modest water-soluble and form less compact microdomains. [9] The influence of this group and of the spacer length and end amount of probe molecules might disturb the interaction between polymers and surfactants. group of the surfactants on the cooperativity of the surfac- tant binding is investigated. In a previous paper we have described the use of UV spectroscopy to study the interaction between polymers and surfactants in which one or both components are labelled with a chromophore. [6] In these systems the chromophores form an intrinsic part of the polymer or surfactant and play Results and Discussion a role in determining their physical behaviour. [7,8] Spectral changes observed upon interaction between these polymers The polyelectrolytes and surfactants used in this paper are shown in Scheme 1. The synthesis and properties of the [a] Wageningen Agricultural University, Department of Biomolecu- surfactants and polyelectrolytes have been described be- lar Sciences, Laboratory of Organic Chemistry, Dreijenplein 8, NL-6703 HB Wageningen, The Netherlands fore. [7-9] Eur. J. Org. Chem. 1999, 305-312  WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999 1434-193X/99/0101-0305 $ 17.50+.50/0 305