Department Seminar: Derrick Hastings
Sep 15, 2022
1:30PM to 2:30PM
Date(s) - 15/09/2022
1:30 pm - 2:30 pm
Title: PolyelectrolyteComplexes: The Effects of Charge Distribution and Charge Density
Date: Thursday, September 15, 2022
Room: ABB 165 (in-person only)
Host: Harald Stover
Polyelectrolytesare widely explored as components in biomaterials due to their ability toundergo spontaneous self-assembly via associative ionic interactions. As aresult, the ability to understand and control the strength of the associativeinteractions inherent in polyelectrolyte complexes is critical in thedevelopment of new technologies with specific properties. Polyelectrolytecomplexation is highly dependent on polymer architecture, including factorssuch as charge distribution and charge density. Synthetic polymers offer theability to investigate various structure-property relationships via an immenserange of accessible polymer structures and compositions. Hence, this workexplores the underlying interactions of polyelectrolyte complexes and theresulting stimuli-responsive complexes using accessible synthetic polymers withspecific compositional parameters.
To evaluatethe effects of charge distribution, polyelectrolytes comprising methacrylicacid (MAA) and N-(3-aminopropyl)methacrylamide hydrochloride (APM) in differentratios were prepared and used to study the interactions of different single-and multicomponent PECs. The complexes were shown to have isoelectric points(pH(I)) at which macroscopic phase separation is induced that are highlydependent on the polymer composition as well polymer mixing ratio, formulti-component PECs. Additionally, these complexes are sensitive to saltshielding effects that are dependent on charge separation, increasing insensitivity with increased intramolecular self-neutralization. The system ofMAA-APM polyelectrolytes was further explored as zwitterionic2-methacryloyloxyethyl phosphorylcholine (MPC) were introduced to theindividual polymers used for three distinct coacervates arrangements. MPCdrastically increased the responsiveness of complexes to pH, [NaCl], andtemperature due to the reduced charge density of the involved polyelectrolytes.
The effects ofcharge density in polyelectrolyte complexation were then studied in polycationcapsule formation for alginate-based cell encapsulation. Low charge densityAPM-MPC polycations were prepared and evaluated as shell-formers with anionicalginate hydrogels for surface complexation, demonstrating that charge densityand polymer hydration impacts the complexation strength and stability,thickness of the polymer coating, mechanical strength of the resultingcrosslinked capsules, and in the protein resistant properties of the capsulesurface. Furthermore, charge density effects were exploited in strongpolyampholyte hydrogels. Physically crosslinked hydrogels using chargedstyrenic monomers exhibit stimuli-responsive and mechanical properties thatwere tunable by reduction in charge density through the addition of MPC and2-hydroxyethyl methacrylate (HEMA). The different ternary polyampholytehydrogels indicate that the capacity for responsive self-healing improves withreduction in charge density.