Adsorption of triblock copolymers and their homopolymers at laponite clay/solution interface. Role played by the copolymer nature

Abstract

The adsorption thermodynamics of copolymers, based on ethylene oxide (EO) and propylene oxide (PO) units, at the laponite (RD) clay/liquid interface was determined at 298 K. The copolymer nature was tuned at molecular level by changing the hydrophilicity, the architecture and the molecular weight (Mw) keeping constant the EO/ PO ratio. Polyethylene (PEGs) and polypropylene (PPGs) glycols with varying Mw and their mixture were also investigated to discriminate the role of the EO and the PO segments in the adsorption process. Enthalpies of transfer of RD, at fixed concentration, from water to the aqueous macromolecule solutions as functions of the macromolecule molality were determined. They were treated quantitatively by means of a model based on two equilibria: (1) one-to-one binding between the macromolecule and the site on the solid and (2) two-to-one binding following which one macromolecule interacts with another one adsorbed onto the solid. The good agreement between the equilibrium constants obtained from calorimetry and those determined from kinetic experiments confirmed the reliability of the experimental and theoretical approaches. Almost all of the systems investigated are highlighted by the one-to-one binding; the L35 and 10R5 systems present both equilibria. The insights provided by the thermodynamics of adsorption of their homopolymers onto RD were fruitful in obtaining detailed information on the nature of the forces involved between RD and the copolymers. The data obtained in the present work clearly evidenced that for comparable polymer Mw, PPG is more suitable in building up a steric barrier around the RD particles and, indeed, exhibits several advantages and no drawbacks. Moreover, the parent copolymers may properly functionalize the RD surface by exploiting both their high affinity to the solid surface and the ability to self-assemble onto it as L35 and 10R5 clearly showed.

Liquid–liquid extraction of metal ions without use of organic solvent

“…However, copolymer ATPS enable the application of the 1N2N, a water-insoluble extractant, since, as pointed out above, the phase enriched in macromolecules has high hydrophobicity. The reagent 1N2N forms highly stable complexes with several metal ions, such as Co(II), Cu(II), Fe(III) and Ni(II) [34] and it has higher selectivity and larger partitioning coefficient.…”

Insight into the Broad Field of Polymer Nanocomposites: From Carbon Nanotubes to Clay Nanoplatelets, via Metal Nanoparticles

“…De Lisi et al studied the thermodynamics of adsorption of triblock copolymers (PEO-PPO-PEO) at the interface of Laponite ® clay/solution when varying the hydrophilicity, the architecture and the molecular weight of the copolymer [168]. Calorimetric results and modeling kinetic data indicated that the architecture of the copolymers did not have a significant influence on the interactions between the Laponite ® platelets and the copolymers.…”

A thermodynamic study to evidence the -dichloroalkane/ block copolymer mixed aggregates formation: Effect of the copolymer architecture

“…They stabilize suspensions [1,2] and undergo aggregation processes that are very thermosensitive [3][4][5]. Therefore, these macromolecules are exploited for various applications (pharmaceutical formulations [6][7][8] and medical uses [6,9], removal of organic contaminants [10][11][12] from soil and water basins, etc.…”