RESUMO
Solution and adsorption properties of both charged and uncharged bottle-brush polymers have been investigated. The solution conformation and interactions in solution have been investigated by small-angle scattering techniques. The association of the bottle-brush polymers with anionic surfactants has also been studied. Surfactant binding isotherm measurements, NMR, surface tension measurements, as well as SAXS, SANS and light scattering techniques were utilized for understanding the association behaviour in bulk solutions. The adsorption of the bottle-brush polymers onto oppositely charged surfaces has been explored using a battery of techniques, including reflectometry, ellipsometry, quartz crystal microbalance, and neutron reflectivity. The combination of these techniques allowed determination of adsorbed mass, layer thickness, water content, and structural changes occurring during layer formation. The adsorption onto mica was found to be very different to that on silica, and an explanation for this was sought by employing a lattice mean-field theory. The model was able to reproduce a number of salient experimental features characterizing the adsorption of the bottle-brush polymers over a wide range of compositions, spanning from uncharged bottle-brushes to linear polyelectrolytes. This allowed us to shed light on the importance of electrostatic surface properties and non-electrostatic surface-polymer affinity for the adsorption. The interactions between bottle-brush polymers and anionic surfactants in adsorbed layers have also been elucidated using ellipsometry, neutron reflectivity and surface force measurements.
RESUMO
Catalysts that can detoxify reactive organic chemicals (electrophiles) could be of potential beneficial use. Electrophilic compounds are common toxic agents that are conjugated to endogenous nucleophiles (i.e. glutathione) in an enzyme catalysed reaction (by glutathione transferases). Here, the properties of newly synthesised polymeric surfactant catalysts, which are glutathione transferase mimics, are described (which are not limited to the glutathione thiol donor). Reactions studied were nucleophilic aromatic substitution with 1-chloro-2,4-dinitrobenzene (CDNB) and thiolysis of p-nitrophenyl acetate. Polymeric quaternary ammonium salts synthesised starting from 2-(dimethyl-amino)ethylmethacrylate or 1,3-bis(dimethylamino)isopropylmethacrylate were used as surfactants. Five polysoaps were studied possessing different charge density and different density of hydrophobic chains. In comparison with cetyltrimethylammonium bromide, the polymeric surfactants were clearly more efficient catalysts (i.e. 4.9 vs. 150 (10(3) per M(2)/s) with benzyl hydrosulfide and CDNB). Polymers with high charge and hydrophobic density were most efficient. With a given catalyst, increasing hydrophobicity of the thiol substrate parallels increasing reaction rates (e.g. 0.7- > or = 37 (10(3) per M(2)/s) with CDNB). Concentration of the substrate in the micellar pseudophase together with solvent shielding is suggested as the underlying rate enhancement mechanism. Dead-end Meisenheimer complex stabilisation, where an extremely electrophilic compound (1,3,5-trinitrobenzene) reversibly interacts with glutathione is seen both with glutathione transferases and the polymeric surfactant catalysts. The degree of stabilisation follows catalytic efficiency and thus supports the above structure activity relationships. In conclusion, polymeric materials that can perform biological functions in detoxication are described, as well as their optimal properties.