Interaction of poloxamer block copolymers with cosolvents and surfactants

The interactions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylen e oxide) (PEO-PPO-PEO) block copolymers (Poloxamers) with cosolvents and su rfactants are addressed here. Ternary isothermal (25 degreesC) systems of P luronic F127 (Poloxamer 407) in the presence of water and polar water-misci ble solvents (glycerol, propylene glycol or ethanol), a partially water-mis cible solvent (glycerol triacetate), a non-ionic surfactant (tetraethylene glycol monooctyl ether, C-8(EO)(4)), an anionic surfactant (sodium dodecyl sulfate, SDS), and a cationic surfactant (cetyltrimethyl ammonium bromide, CTAB) have been investigated by phase behavior studies and small angle x-ra y scattering (SAXS). A number of regions with different lyotropic liquid cr ystalline structure have been identified in each ternary Poloxamer-water-co solvent/surfactant system. For a given Poloxamer, the composition range ove r which a given self-assembled structure is stable varies according to the cosolvent/surfactant type land properties). The effects that the different cosolvents or surfactants exhibit on the Poloxamer phase behavior are inter preted in terms of the preference of the cosolvent/surfactant molecules to locate in different domains of the PEO-PPO-PEO block copolymer self-assembl y. Organic solvents, depending on their relative polarities, locate prefera bly in the PEG-rich or the PPO-rich domains of the microstructure. Some sol vents (e.g, ethanol and glycerol triacetate) may show amphiphilic behavior and act as cosurfactants by preferably locating at the interface between th e PEG-rich and the PPO-rich domains. The location of the solvents in the bl ock copolymer assemblies is established by an analysis of the trends in the structure lattice spacing (obtained from SAXS) and the interfacial area pe r block copolymer molecule. (C) 2001 Elsevier Science B.V. All rights reser ved.