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The damping coefficient and the length of transversal (at the frequencies from 100 to 300 Hz) and longitudinal (at the frequencies from 0.1 to 3 Hz) surface waves have been measured as a function of the concentration of solutions of poly(ethylene glycol)s (PEG) and poly(ethylene oxide) (PEO), and the molecular weight of the polymer. A local maximum of the damping coefficient of transversal waves has been discovered for dilute solutions of PEG 400. This maximum disappears and the damping coefficient decreases monotonically with the concentration of polymers of higher molecular weight in the region of dilute solutions. A fast increase of the damping with concentration has been discovered for semidilute solutions. These experimental data are used for the calculation of the real and imaginary components of the dynamic surface elasticity as a function of concentration and frequency. The obtained dependencies can be explained with the help of a dynamic model of the surface layer of polymer solutions where the main relaxation processes are connected with the monomer exchange between different regions of the surface layer. In the investigated concentration range, the corresponding relaxation time determined from the experimental data changes by more than 2 orders of magnitude.

The dynamic surface elasticity of mixed aqueous poly(styrenesulfonate)/alkyltrimethylammonium bromide solutions has been measured by the oscillating barrier, oscillating drop, and capillary wave methods as a function of time and surfactant concentration. At low surfactant concentrations (<0.3 mM) the surface viscoelastic behavior is close to that of relatively concentrated pure PSS solutions. The classical Goddard et al. model cannot explain all the experimental results in this concentration range, and a modification of this model is proposed. At intermediate concentrations the real part of the dynamic surface elasticity drops abruptly by almost 1 order of magnitude. This feature can be connected with the formation of a heterogeneous surface film in accordance with recent results by Monteux et al. (Langmuir 2004, 20, 57). At high surfactant concentration (>2 mM) the modulus of the dynamic surface elasticity is low and the adsorbed film is viscoelastic.

We describe a new methodology to prepare loaded polyelectrolyte/surfactant films at the air/water interface by exploiting Marangoni spreading resulting from the dynamic dissociation of hydrophobic neutral aggregates dispensed from an aqueous dispersion. The system studied is mixtures of poly(sodium styrene sulfonate) with dodecyl trimethylammonium bromide. Our approach results in the interfacial confinement of more than one third of the macromolecules in the system even though they are not even surface-active without the surfactant. The interfacial stoichiometry of the films was resolved during measurements of surface pressure isotherms in situ for the first time using a new implementation of neutron reflectometry. The interfacial coverage is determined by the minimum surface area reached when the films are compressed beyond a single complete surface layer. The films exhibit linear ripples on a length scale of hundreds of micrometers during the squeezing out of material, after which they behave as perfectly insoluble membranes with consistent stoichiometric charge binding. We discuss our findings in terms of scope for the preparation of loaded membranes for encapsulation applications and in deposition-based technologies.