Aqueous phase/nanoparticles interface: hydroxypropyl cellulose adsorption and desorption triggered by temperature and inorganic salts

Abstract

The study highlighted the main forces driving the adsorption of hydroxypropyl cellulose (HPC) onto clay nanoparticles with a disk-like shape (Laponite RD). Modeling the isothermal titration calorimetry data provided the key thermodynamic properties, which enabled us to discuss the microscopic aspects contributing to the energetic and the entropic changes of the polymer adsorption at the nanoparticle/liquid interface. We evidenced that the process is strongly enthalpy-driven and that the interactions lead to constraints of the HPC configuration at interface. The functionalized nanoparticles enhanced the polymer solubility in water expanding the one-phase area of the binodal curve. Temperature and salts change the forces of adsorption and, furthermore, salts generate a dramatic reduction of the HPC solubility in water in the presence of Laponite RD.