Friction Control by Adsorption of Polymer Brush Nanoparticles

This dissertation investigates the adsorption of polymer brush nanoparticles (BNPs) at the solid/liquid interface and interactions between BNP coated surfaces undergoing compression and sliding. BNPs are a class of materials defined by their nanoscale core and surrounding spherical brush layer of polymer arms. BNPs developed in this dissertation are created using atom transfer radical polymerization (ATRP) and include polymer grafted silica nanoparticles, star polymers with a corona of arms crosslinked with a dense hydrophobic core, and star polymers with arms emanating from a multi-functional molecular core. Assemblies of BNPs at the solid liquid interface can attain relatively low or high surface coverages which, when paired with a responsive polymer brush nanoparticle, enables additional control of interactions between BNP adsorbed layers via tunable surface coverage and particle-surface bridging forces. Strategies for controlling the adsorption and packing of these BNPs are presented, and surface forces between BNP coated surfaces are measured to assess each type of BNP’s ability to control friction and adhesion between silica surfaces. Direct adsorption strategies which produce single BNP type adsorbed layers, and sequential adsorption strategies which form surfactant/BNP, polyelectrolyte/BNP, and BNP/BNP mixed layers are employed to generate a full suite of surface coatings with uniquely-engineered structural, frictional, and adhesive characteristics.