This book describes multi-functional composites that were synthesized using organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermoresponsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. The second broad object was to fabricate polymer-ceria colloidal particles for abrasive applications such the chemical mechanical planarization of silicon oxide wafers. Nanoparticles of ceria were chosen to exploit the density and surface that is devoid of appreciable surface charges.