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New chain transfer agents based on dithiobenzoate and trithiocarbonate for free radical polymerization via Reversible Addition-Fragmentation chain Transfer (RAFT) were synthesized. The new compounds bear permanently hydrophilic sulfonate moieties which provide solubility in water independent of the pH. One of them bears a fluorophore, enabling unsymmetrical double end group labelling as well as the preparation of fluorescent labeled polymers. Their stability against hydrolysis in water was studied, and compared with the most frequently employed water-soluble RAFT agent 4-cyano-4-thiobenzoylsulfanylpentanoic acid dithiobenzoate, using UV-Vis and 1H-NMR spectroscopy. An improved resistance to hydrolysis was found for the new RAFT agents, providing good stabilities in the pH range between 1 and 8, and up to temperatures of 70°C. Subsequently, a series of non-ionic, anionic and cationic water-soluble monomers were polymerized via RAFT in water. In these experiments, polymerizations were conducted either at 48°C or 55°C, that are lower than the conventionally employed temperatures (>60°C) for RAFT in organic solvents, in order to minimize hydrolysis of the active chain ends (e.g. dithioester and trithiocarbonate), and thus to obtain good control over the polymerization. Under these conditions, controlled polymerization in aqueous solution was possible with styrenic, acrylic and methacrylic monomers: molar masses increase with conversion, polydispersities are low, and the degree of end group functionalization is high. But polymerizations of methacrylamides were slow at temperatures below 60°C, and showed only moderate control. The RAFT process in water was also proved to be a powerful method to synthesize di- and triblock copolymers including the preparation of functional polymers with complex structure, such as amphiphilic and stimuli-sensitive block copolymers. These include polymers containing one or even two stimuli-sensitive hydrophilic blocks. The hydrophilic character of a single or of several blocks was switched by changing the pH, the temperature or the salt content, to demonstrate the variability of the molecular designs suited for stimuli-sensitive polymeric amphiphiles, and to exemplify the concept of multiple-sensitive systems. Furthermore, stable colloidal block ionomer complexes were prepared by mixing anionic surfactants in aqueous media with a double hydrophilic block copolymer synthesized via RAFT in water. The block copolymer is composed of a noncharged hydrophilic block based on polyethyleneglycol and a cationic block. The complexes prepared with perfluoro decanoate were found so stable that they even withstand dialysis; notably they do not denaturate proteins. So, they are potentially useful for biomedical applications in vivo.
The goal of this work was to study the binding of ions to polymers and lipid bilayer membranes in aqueous solutions. In the first part of this work, the influence of various inorganic salts and polyelectrolytes on the structure of water was studied using Isothermal Titration Calorimetry (ITC). The heat of dilution of the salts was used as a scale of water structure making and breaking of the ions. The heats of dilution could be attributed to the Hofmeister Series. Following this, the binding of Ca2+ to poly(sodium acrylate) (NaPAA) was studied. ITC and a Ca2+ Ion Selective Electrode were used to measure the reaction enthalpy and binding isotherm. Binding of Ca2+ ions to PAA, was found to be highly endothermic and therefore solely driven by entropy. We then compared the binding of ions to the one-dimensional PAA polymer chain to the binding to lipid vesicles with the same functional groups. As for the polymer, Ca2+ binding was found to be endothermic. Binding of calcium to the lipid bilayer was found to be weaker than to the polymer. In the context of these experiments, it was shown that Ca2+ not only binds to charged but also to zwitterionic lipid vesicles. Finally, we studied the interaction of two salts, KCl and NaCl, to a neutral polymer gel, PNIPAAM, and to the ionic polymer PAA. Combining calorimetry and a potassium selective electrode we observed that the ions interact with both polymers, whether containing charges or not.