Effect of intercalated chitosan/clay nanostructures on concentrated pluronic F127 solution: A FTIR-ATR, DSC and rheological study

Hypothesis: The thermoreversible gel-like behavior of pluronics can be affected by the presence of drugs or cosolvents. So far, the effects of polysaccharides and of clays singularly added on a pluronic water dispersion were investigated and the gelation and viscoelastic properties tuned by properly varying the concentration of the additives. The combined addition of chitosan and montmorillonite opens the possibility to join the properties of the single constituents to formulate bio-based temperature-sensitive vehicles. Experiments: Chitosan, montmorillonite and chitosan-montmorillonite nanocomposites were added on a concentrated pluronic F127 aqueous solution. The pluronic-based systems were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), rheology and Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR). The gelation and micellization behaviors of pluronic were compared to those of the pluronic-based composites and analyzed in terms of the different elasticity of the investigated samples. Then, FTIR-ATR spectroscopy was applied to analyze different vibrational modes in order to evidence differences in the conformational arrangements of the micelles. Findings: The experiments evidenced that the chitosan/clay nanocomposites have a destructuring effect on the micellar arrangements of pluronic and that the chaotropic effect by chitosan dominates over the ordering effect by the clay.