The local environment of a drug molecule in polymeric drug nanocarrier solutions impacts the bioavailability of the drug and its ability to reach its target in the biological system. The local environment and aggregation properties of small, hydrophobic molecules in aqueous polymeric micelles and nanocarrier aggregates are explored using fluorescence spectroscopy for the purpose of characterizing drug delivery formulations on molecular length scales. The fluorescence properties of seven

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... dyes in A-B-A triblock copolymer unimer, micelle, and gel solutions respond to changes in local solvent environment. The A-B-A copolymer is used as a model for the encapsulationproperties of three novel amphiphilic polymers designed for hydrophobic drug delivery. Rilpivirine, a novel HIV inhibitor shows solvatochromic fluorescence spectral response due to a large charge transfer between the ground and electronic excited states. The fluorescence of rilpivirine in A-B-A triblock copolymer is investigated as a method to differentiate between the aggregated and unimer forms of the solubilized drug.