Kinetics and Applications of Polyelectrolyte Membranes and Multilayers

Polyelectrolytes can be used in a variety of forms from Layer-by-Layer assembled thin films to spun polyelectrolyte complex as free-standing membranes. The Layer-by-Layer methodology is used to adsorb oppositely charged polyelectrolytes to a substrate for use across a variety of applications depending on their construction and functionalization. This process is achieved by the alternating solution deposition of positively and negatively charged polyelectrolytes with intermediate rinsing steps. Applications of these thin films lie in biocompatible coatings, anti-corrosion surfaces, hydrophilic and hydrophobic coatings, and chromatographic applications among several others. Polyelectrolyte solutions can also be directly mixed sans-substrate to produce polyelectrolyte complexes, which can be processed into extruded morphologies or dissolved in salt to form coacervates, which can then be spun into free-standing membranes. Polyelectrolyte complex membranes have applications in ion selectivity and permeability as well as desalination. In this dissertation, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS) are used to form polyelectrolyte complex (PEC) by solution mixing. The PEC is then rinsed of salt and dried to produce a tough orange solid, which is ground into a fine powder and dissolved in KBr to produce polyelectrolyte coacervate (PECOV). The coacervate phase exists between [KBr] 1.3-1.8 M, so 1.7 M KBr and 1.9 M KBr concentrations are studied using spin-coating to determine the behavior of a PECOV against a polyelectrolyte solution. Using a specific set of parameters, spun films of PEC can be removed from an aluminum substrate for use as free-standing membranes. A different set of polyelectrolytes is used to study the ability of a PEMU to prevent both mammalian cell and bacterial adhesion to a surface. The polyelectrolytes used are poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA), with the latter being functionalized with benzophenone (Bp) and 3-[2-(acrylamido)-ethyl dimethylammonio] propane sulfonate (AEDAPS) in different stages during buildup. Benzophenone is used as a photocrosslinking agent to create a tough multilayer on which to build the zwitterion-functionalized layers. Despite the superb ability of these multilayers to repel mammalian cell lines A7r5 and 3T3, the PEMU produced attracts bacteria in an accelerated fashion, creating an interesting contradictory behavior. Production of PEMUs by Layer-by-Layer assembly is a widely used method and is well understood. The kinetics of this polyelectrolyte sorption is not, however. Using PDADMAC and PSS, rotating disk electrochemistry (RDE) is used to measure the rate at which 1.0 M and 0.1 M PSS adsorbs to a PDADMAC-terminated PEMU. Six different narrow molecular weights are used at both concentrations to determine the behavior of PSS based on chain length. Low molecular weight PSS is only diffusion limited by the solution and adsorbs to the PEMU quickly, while higher molecular weight PSS chains are hindered in their ability to adsorb based on the availability of extrinsic positive sites from excess PDADMAC as well as the rate in which they diffuse through solution.