Solvent-Tuned Block-Copolymer Self-Assembly and Disassembly

Amphiphilic block copolymers of the poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) family are well-known for self-assembling in water (selective solvent for PEO) into (core-shell spherical) micelles, and, at higher concentrations, into cubic, hexagonal, and lamellar lyotropic liquid crystals. We are interested on how the aqueous phase behavior and structure of these polymeric amphiphiles can be modulated by the addition of polar organic solvents (e.g., glycerol, ethanol, propylene carbonate, triacetin). Mixtures of water with two organic solvents constitute a specific focus of this work. Our studies combine macroscopic observations (e.g., phase boundaries, viscosity) with microscopic measurements (using spectroscopy and small-angle X-ray scattering), and aim to relate the type of structure formed and its characteristic dimensions to the relative swelling of the polymer blocks and to the location of the solvent in the amphiphile assembly. Solvent-induced structural changes of block copolymers have interesting repercussions on formulations and nanomaterials synthesis in such media.