Clean and green: Copper(I) complexes of phenanthroline‐based ligands anchored on the chitosan polymer are good catalysts for the “click” cycloaddition of azides with terminal alkynes (see scheme; the scanning electron microscopy image shows the porous structure of the catalyst). These heterogeneous catalytic systems do not require a base or reducing agent and operate in alcohol or water.

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The interaction between two hydrophilic polyelectrolytes of opposite charges was investigated using poly­(l-lysine) (PLL) as the polycation and a library of copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (P­(AM-co-AMPS)) with various chemical charge densities as polyanions. The formation of polyelectrolyte complexes (PECs) was comparatively studied by varying different parameters, such as the mixing order, the P­(AM-co-AMPS) chemical charge density and the initial polycation to polyanion molar ratio. PECs were then characterized in terms of charge stoichiometry and of stability toward ionic strength. The results showed a strong dependency of precipitated PEC stoichiometry on the P­(AM-co-AMPS) chemical charge density and the initial polycation to polyanion molar ratio. In contrast, PEC stoichiometry was not affected by the mixing order of the two polyelectrolyte partners. A general rule capable of predicting the PEC stoichiometry is proposed.

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Ein Biopolymer zur Unterstützung: An Chitosan verankerte Kupfer(I)‐Komplexe verschiedener Phenanthrolin‐Liganden sind gute Katalysatoren für die Cycloaddition von Aziden mit terminalen Alkinen (siehe Schema; das SEM‐Bild zeigt die poröse Struktur des Katalysators). Diese heterogenen Katalysesysteme benötigen weder Basen noch Reduktionsmittel und können in Alkohol oder Wasser effizient eingesetzt werden.

In this study, binding of linear poly(l-lysine) to a series of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate copolymers was examined by isothermal titration calorimetry (ITC). Binding constant and stoichiometry were systematically determined at different ionic strengths and for different polyanion charge densities varying between 15% and 100%. The range of investigated ionic strengths was carefully adjusted according to the polyanion charge densities to get measurable binding constants (i.e., formation binding constant typically comprised between 10 and 10 M) by isothermal titration calorimetry (ITC). The number of released counterions during the polyelectrolyte complex formation was determined from the log-log dependence of the binding constant according to the ionic strength and was compared to the total number of condensed counterions estimated from the Manning theory. Experimental results obtained by ITC are in very good agreement with those previously obtained by frontal analysis continuous capillary electrophoresis (FACCE) and can be used to model and predict the binding parameters at any ionic strength or any polyanion charge density. Thermodynamic parameters of the complexation between the oppositely charged polyelectrolytes confirm that the complex formation was entropically driven together with a favorable (but minor) enthalpic contribution. For the first time, specificities, advantages/disadvantages of ITC, and FACCE techniques for studying polyelectrolyte complexations are compared and discussed, using the same experimental conditions.

In this work, a systematic study of the interactions between poly(l-lysine) and variously charged statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been carried out by frontal analysis continuous capillary electrophoresis (FACCE). FACCE was successfully implemented to obtain the interaction parameters (binding constant and stoichiometry) at different ionic strengths and for different PAMAMPS charge densities varying between 15% and 100%. The range of investigated ionic strengths was carefully adjusted according to the PAMAMPS charge density to obtain measurable binding constants by FACCE (i.e. formation binding constant typically comprised between 10 and 10 M). The number of released counter-ions during the polyelectrolyte complex formation was systematically quantified via the ionic strength dependence of the binding constant and was compared to the total condensed counter-ion reservoir according to Manning theory on counter-ion condensation. A descriptive and predictive model relating the physico-chemical properties of the two partners, the binding constant and the ionic strength is proposed in the framework of multiple independent interaction sites of equal energy.