UCLA

This dissertation elucidates the significance of macromolecular design in two types of systems - (i) covalently-linked polyurethane networks and composites, and (ii) complexes of oppositely charged polymers (polyelectrolyte complexes) – unified by their macromolecular nature, yet distinguished by their design, governing principles, and applications. The first part of this dissertation highlights the profound effect of the chemistry of flexible polyurethane foams on their physico-mechanical and thermochemical properties; by harnessing these correlations, a simple strategy has been proposed for the facile classification of post-consumer-use flexible polyurethane foams for their chemical recycling. Following this, the upcycling of depolymerized polyurethane products (polyols) into lightweight high-strength organic-inorganic composites with superior thermal insulation and acoustic barrier performance has been discussed. The amenability of the compositing strategy with polyols from different sources, varying chemistries of the diisocyanate linker, and types of inorganic materials have been highlighted. This dual approach is a step toward enabling the circularity of post-consumer-use flexible polyurethane foam and informing the design of polyurethane-inorganic composites with unique properties. The second part of this dissertation delineates the phenomenon of polyelectrolyte complexation and examines the non-trivial role of salt ion valency and polyelectrolyte length asymmetry on complexation. Divalent ions have been shown to reverse the composition of PECs, favoring their sequestration in the complex phase, and hindering chain relaxation. Following this, the dramatic influence of polyelectrolyte length symmetry in controlling the polymer content of the complex phase has been discussed in the context of thermodynamics and the Voorn-Overbeek theory. Furthermore, length-asymmetry will be shown to alter the viscosity of the complex phase. These dual studies are aimed to serve as design guides for polyelectrolyte complexation occurring in environments (biological and medical systems, environmental and wastewater treatment applications) where little to no control can be exercised over the properties of the solution and polyelectrolytes.