(289f) Structure and Dynamics of Polyelectrolyte Complex Hydrogels

Polyelectrolyte complexes (PEC) form when oppositely charged polyelectrolyte chains spontaneously associate and phase separate in aqueous media. Combining one or both polyelectrolyte chains with a neutral polymer restricts bulk phase separation of the PECs, and thus leads to self-assembled structures with PEC domains surrounded by neutral polymer coronae, forming micelles and hydrogels. The PEC domains in these assemblies can encapsulate therapeutics as well as genetic materials and thus have tremendous potential in drug delivery and tissue engineering applications.

We will present insights on the equilibrium structure as well as nanoscale and bulk dynamics of PEC hydrogel assemblages comprising oppositely charged block copolyelectrolytes. Detailed investigations of structure-dynamics-rheology relationships of hydrogels comprising model block copolyelectrolytes with oppositely charged functionalized polyallyl glycidyl ethers as ionic and polyethylene glycol as neutral blocks will be discussed. X-ray scattering investigations provide a comprehensive structural description of these materials, revealing large-scale ordering of the nanoscale PEC domains at moderate to high polymer loadings accompanied by a disorder-order transition and subsequent morphological transitions. Influence of the nanoscopic structure on nanoscale dynamics and bulk rheology will be elucidated via a mapping the hydrogel relaxation times, ascertained from XPCS measurements, and bulk moduli on the PEC morphology landscapes. The effect of key parameters such as polymer block lengths and concentration on the relationship between the nanoscale PEC morphology and equilibrium material properties will also be elaborated.