Polymer Membranes for Advanced Applications in Gas Separation and Biosensor Coatings

<p>Polymer materials are an integral component of our modern world due to their low cost, ease of processability, and tailorable physical and chemical properties, which make them suited to a multitude of applications, including membrane-based gas separations and protective, antifouling coatings for biological sensors. This dissertation addresses both applications through the development of novel Friedel-Crafts polymer membranes and synthesis of surface-initiated polymer brushes within nanoporous biosensors. </p> <p>Following an overview of polymerization methods, recent advances, and state of development in both applications, presented in Chapter 1, the first two chapters of this dissertation utilize the Friedel-Crafts (F-C) polycondensation to produce polymers with systematically varied substitutions and sequences for structure-property investigations into polymer design and gas separation performance. In Chapter 2, two series of triarylmethane-based F-C polymers were synthesized, wherein the size and geometry of R1 or R2 substituent was varied to identify how the key structural components affected gas transport. Increases in substituent size, the degree of substituent branching, or introducing fused rings to the R2 substituent resulted in decreased film densities and increased gas permeabilities, with branched and cyclic substituents seeing increased size sieving. In Chapter 3, the segmental sequence of F-C copolymers was varied through the synthesis of homo, random, and multiblock polymers and copolymers. Extensive investigation of the copolymers’ gas transport properties revealed that modulating both the ratio of the constituent block lengths and the number of blocks impacted gas permeability through changes in copolymer packing and the creation of subdomains. </p> <p>Transitioning from gas separation membranes, Chapter 4 analyzes the growth of polymer brushes throughout nanoporous gold electrodes through electrochemical and spectroscopic methods. Optimal polymerization conditions were identified for the synthesis of a dense and robust brush throughout the hierarchical pore volume. From the insights gathered in Chapter 4, Chapter 5 explores the polymer-coated nanoporous electrodes sensing capabilities and resistance to biological fouling. Thinner brushes polymerized for short to moderate timeframes exhibited signal gains comparable to the bare electrode through clinically relevant concentrations and without impacting analyte diffusion. Finally, Chapter 6 includes concluding remarks and details the future experiments underway.</p>