| Description |
This dissertation describes the synthesis and characterization of ion-conducting polymer-modified silica nanoparticles. This dissertation explores the use of polymermodified silica nanoparticles for application in lithium-ion batteries and fuel cells. Silica nanoparticles provide an advantageous platform for growth of polymer brushes while providing mechanical and chemical stability. The use of polymer-modified silica nanoparticles as building blocks for solid polymer electrolytes was investigated first. Silica nanoparticles were modified with two different lengths of polymer brushes containing short side-chains of ether oxygens. Lithium salt addition was found to increase the glass transition temperature and the degradation temperature of the material. The ion conductivity of the polymer-modified silica nanoparticles was determined using impedance spectroscopy. The lithium-ion conductivity was further studied by modifying silica nanoparticles with polymer brushes containing longer ether oxygen side-chains. Lithium salt addition only had effects on the glass transition temperature for the polymer brushes with the longer side-chains. The lithium-ion conductivity was studied as a function of ether oxygen side-chain length. Silica nanoparticles modified with longer side-chains were found to have higher ionic conductivity than the nanoparticles modified with the short side-chain polymers. Lastly, polymer-modified silica nanoparticles were employed to prepare polymer iv exchange membranes for use in fuel cells. Two types of proton conductive membranes were prepared, self-assembled, and pressed. Bottle-brush type polymer brushes were prepared on the surface of silica nanoparticles and used to make self-assembled membranes. This architecture added mechanical strength to the overall membrane under humid conditions. The proton conductivity was explored as a function of polymer brush architecture. It was determined that proton conductivity was solely a function of sulfonic acid content and not due to the different polymer brush architecture. Mixed nanoparticle membranes were prepared by mixed two different types of polymer-modified nanoparticles and pressing them into a die set. Proton conductivity was explored as a function of the ratio of the two types of polymers. The proton conductivity was an order of magnitude higher for the membrane containing the higher ratio of sulfonic acid groups. |
