PHYSICAL CHEMISTRY OF COLLOIDAL-NANOPARTICLE INTERACTIONS

Following the advances in the design and characterization of engineered nanoparticles, biomaterials came into contact with the nano-world. Among many implementations of bio-nanotechnology, there is an increasing scientific and industrial interest in designing complex/hybrid structures (micro/macro) by merging the advantageous of inorganic colloidal particles (fixed shape, hard matter) with organic biopolymers (flexible shape, soft matter).In the current dissertation, nanostructured silica suspensions with tunable rheological characteristics were designed via steric and electrostatic interactions. Perturbation of short range interactions, protein bridging and silica re-dispersion were reported to play key roles in the macro-structure formation as determined by light scattering, steady state shear and small angle oscillatory shear rheology. Tunable rheology was attributed to the physiochemical interactions of disordered fractal microstructures that are formed via spontaneous, non-directional and random complexation. The thermodynamic nature of complexation was resolved by discriminating the free energy change into its enthalpic and entropic contributions through circular dichroism and isothermal titration calorimetry. The dominant entropic pathway of complexation, showed that the assembly of supra-colloid microstructures by using nano-particles and biopolymers as building blocks is not limited by unfavorable enthalpic restrictions