When 10:30 AM - 12:30 PM Jan 12, 2018
Where NCRC Bldg. 10, Room G064
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PhD Dissertation Defense: Effect of Ternary Additives on the Evolution of Structure Formation in Aqueous PEO-PPO-PEO Micelles


Andre Thompson
MSE PhD candidate

The rationale for understanding how ternary additives perturb the micelle formation energetics and where within the micelle ternary additives are partitioned is key to resolving how formulated micelles perform as drug delivery vehicles. We expanded our understanding of the micellization process of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymer solutions with varying hydrophilicities, and how ternary additives perturb the micelle formation energetics.

Differential scanning calorimetry was performed on a series of aqueous solutions of PEO-PPO-PEO amphiphiles co-formulated with ternary additives to resolve the critical micelle concentrations and any deviation in the enthalpy of micelle formation. Enthalpy-entropy compensation plots revealed both drug-influenced compensation and drug-invariant behavior.

Small-angle x-ray scattering was used to investigate the evolution and breakdown of the structures formed in neat PEO-PPO-PEO solutions and co- formulated with a drug with increasing temperature. Added drug changed the nucleation behavior for fcc or bcc phases within the sample from a homogenous process to a more heterogeneous distribution of nucleated species. Added drug

also either enhanced the structural ordering or destabilized the order phases. Dynamic diffusion experiments were performed on polymeric micelles gels mixed with ternary additives at room temperature and 40oC to gauge their release from sequestered structures using ultraviolet-visible spectroscopy. The permeation behavior of the added drug resulted in a burst delivery after the first 5 hours. The higher fluence at elevated temperature is attributed to reducing the blocking effect of the amphiphiles on the walls of the dialysis tubing as colloidal gels are formed. There may be a correlation between higher temperature and higher overall permeability if the membrane pores also expand with temperature.

Lastly, vertical flame tests, thermal gravimetric analysis, micro-scale combustion calorimetry, and scanning electron microscopy were all used to test for flammability and coating quality of fire retardant-encapsulated micelle gels coated onto cotton fabrics. After coating, if ignition occurred, the fabric would self- extinguish. While there is a need to optimize the coating conditions to yield an appropriate thickness, the combination of flame retardants packaged in an amphiphilic matrix raises cotton flame retardancy. Overall, a greater understanding of the interactions between amphiphilic copolymer solutions and dissolved ternary additives was achieved.