Cylindrical polyelectrolyte-comb-surfactant complexes

Quaternized polymer combs based on poly(2-vinylpyridine-macromonomers) and the surfactant sodium dodecylsulfate are employed in the synthesis of a novel cylindrical polyelectrolyte-comb-surfactant complex (PECSC). The complex formed has 1:1 stoichiometry with respect to the ratio of dodecylsulfate to pyridinium units. It is soluble in organic solvents such as 2-butanol or chloroform. Characterization of single particle properties of the complex in organic solution is possible and yields a radius of gyration of 〈Rg〉z = 78.4 nm, a hydrodynamic radius of 〈1/Rh〉z−1 = 51.4 nm and a cross-sectional radius of Rg,cross = 3.9 nm in chloroform. The characteristic ratio γ = 〈Rg〉z/〈1/Rh〉z−1 decreases from γ = 1.73 for the original quaternized polymer comb, indicating the semi-flexible, cylindrical nature of the macromolecules in aqueous solution, to γ = 1.53 for the complex in chloroform. The effect of the main-chain stretching accompanied by the increase of the volume of the comb by introduction of the surfactant is smaller as compared to the electrostatic interactions in the parent comb. This is also reflected in the persistence length lp, which is determined by SANS, and found to be 21.3 nm for the complex and 24.4 nm for the polyelectrolyte comb. In addition, AFM investigations of the polymers adsorbed onto mica showed a 2D-equilibrium adsorption for the complex and a kinetically dominated adsorption process in case of the polyelectrolyte comb.