Mapping Equilibrium and Non-Equilibrium Structural Evolution in Semi-Dilute Polymer Solutions and Hydrogels

Motivated by the central role interactions, such as hydrogen bonding, play in the structuring of biological and biomedical systems and industrial formulations, we experimentally investigate the structure of a range of semi dilute water-soluble polymer solutions. We detail, primarily through small-angle scattering (primarily SANS), the equilibrium and non-equilibrium temporal changes in polymer conformation in response to polymer concentration, temperature and changes in solvent conditions through addition of non-solvents and salts. We centre our investigations on ubiquitous poly(vinyl alcohol), agarose, and sodium carboxymethyl cellulose in semi dilute solution and their trajectories towards and across phase boundaries. With these model systems, we compare and contrast the effects of varying backbone flexibility, polymer-solvent interactions and specific ion effects on polymer solution structuring and its temporal evolution across multiple length scales (from Å to 100 s nm). We place our results in the context of scaling theories and discuss cases where our results agree and fall outside of these theoretical frameworks. Our results inform the rational design of polymer nano- and mesoscale structure in a range of polymer materials with promise for control of molecular and fluid transport across a range of applications.