Original α-aminobisphosphonate-based copolymers were synthesized and successfully used for actinide complexation. For this purpose, poly(α-chloro-ε-caprolactone-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(α-chloro-ε-caprolactone-co-ε-caprolactone) copolymers were first prepared by ring-opening copolymerization of ε-caprolactone (εCL) and α-chloro-ε-caprolactone using poly(ethylene glycol) (PEG) as a macro-initiator and tin(II) octanoate as a catalyst. The chloride functions were then converted to azide moieties by chemical modification, and finally α-aminobisphosphonate alkyne ligand (TzBP) was grafted using click chemistry, to afford well-defined poly(αTzBPεCL-co-εCL)-b-PEG-b-poly(αTzBPεCL-co-εCL) copolymers. Three copolymers, showing different α-aminobisphosphonate group ratios, were prepared (7, 18, and 38%), namely, CP8, CP9, and CP10, respectively. They were characterized by 1H and 31P NMR and size exclusion chromatography. Sorption properties of these copolymers were evaluated by isothermal titration calorimetry (ITC) with neodymium [Nd(III)] and cerium [Ce(III)] cations, used as surrogates of actinides, especially uranium and plutonium, respectively. ITC enabled the determination of the full thermodynamic profile and the calculation of the complete set of thermodynamic parameter (ΔH, TΔS, and ΔG), with the Ka constant and the n stoichiometry. The results showed that the number of cations sorbed by the functional copolymers logically increased with the number of bisphosphonate functions borne by the macromolecular chain, independently of the complexed cation. Additionally, CP9 and CP10 copolymers showed higher sorption capacities [21.4 and 34.0 mg·g–1 for Nd(III) and 9.6 and 14.3 mg·g–1 for Ce(III), respectively] than most of the systems previously described in the literature. CP9 also showed a highest binding constant (7000 M–1). These copolymers, based on non-toxic and biocompatible poly(ε-caprolactone) and PEG, are of great interest for external body decontamination of actinides as they combine high number of complexing groups, thus leading to great decontamination efficiency, and limited diffusion through the skin due to their high-molecular weight, thus avoiding additional possible internal contamination.
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 104 and 106 M–1) 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 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 10⁴ and 10⁶ M–¹) 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.
We report the ionothermal carbonization (ITC) of lignocellulosic biomass in imidazolium tetrachloroferrate ionic liquids (ILs) as an advantageous approach for the preparation of nanostructured carbonaceous materials, namely, ionochars. In a previous study, we investigated the role of the imidazolium cation and demonstrated the possibility of controlling both the textural and morphological properties of ionochars by cation engineering. Although essential for providing intermediate Lewis acidity and relatively high thermal stability, the role of the chloroferrate anion is still open to debate. Herein, we investigated the ITC of sugarcane bagasse and its main component, cellulose, in 1-alkyl-3-methylimidazolium ILs with different chloroferrate anions. We identified anionic speciation and its impact on the properties of the IL by Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The obtained ionochars were characterized by gas physisorption, electron microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and 13C solid-state CP-MAS NMR spectroscopy. We show that the anionic species have a predominant impact on the textural and morphological properties of the ionochars.
