(50d) Tuning Self-Assembled Block Copolymer Micelles Via Co-Solvent Addition

Block copolymer micelles, assembled in selective solvents, have wide ranging applications, from drug delivery to personal care products to nanoreactors. A convenient method of tuning the self-assembly of block copolymer micelles is the addition of co-solvents, which modify the core-corona interfacial tension. The structure of biocompatible poly(ethylene oxide-b-ε-caprolactone) (PEO-PCL) diblock copolymers in deuterated water (D₂O) / tetrahydrofuran (THF_d8) mixtures were investigated with a combination of small-angle neutron scattering (SANS) and nuclear magnetic resonance (NMR). PEO-PCL block copolymers of varying molecular weight but constant block ratio formed spherical micelles over a wide range of solvent compositions (10 to 60% volume THF_d8 in D₂O). Variation of the THF_d8 content in the solvent led to changes in the solvent uptake of the micelle cores, which was similar for both series of differing polymer molecular weight. However, the two series of differing molecular weight showed drastically different trends in the aggregation number, and therefore micelle size parameters, as a function of solvent composition. The unimer content, as determined by NMR, allowed refinement of extracted micelle parameters. The presence of THF_d8 in the micelle cores serves as a model cargo molecule; in ongoing studies these results are extended to the incorporation of relevant therapeutic drug molecules in the micelles.