title: Aqueous multiphase systems of polymers and surfactants provide self-assembling step-gradients in density.
abstract: This Communication demonstrates the generation of over 300 phase-separated systems-ranging from two to six phases-from mixtures of aqueous solutions of polymers and surfactants. These aqueous multiphase systems (MuPSs) form self-assembling, thermodynamically stable step-gradients in density using a common solvent, water. The steps in density between phases of a MuPS can be very small (Δρ ≈ 0.001 g/cm(3)), do not change over time, and can be tuned by the addition of co-solutes. We use two sets of similar objects, glass beads and pellets of different formulations of Nylon, to demonstrate the ability of MuPSs to separate mixtures of objects by differences in density. The stable interfaces between phases facilitate the convenient collection of species after separation. These results suggest that the stable, sharp step-gradients in density provided by MuPSs can enable new classes of fractionations and separations based on density.
authors.affiliation: Department of Chemistry & Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Mace
authors.forename: Ozge
authors.initials: O
authors.lastname: Akbulut
authors.forename: Ashok A
authors.initials: AA
authors.lastname: Kumar
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Shapiro
authors.forename: Ratmir
authors.initials: R
authors.lastname: Derda
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Patton
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
mesh_terms: D002499:Centrifugation, Density Gradient; D011108:Polymers / Q000737:chemistry / Q000302:isolation & purification*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry / Q000302:isolation & purification*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D011108:Polymers; D013501:Surface-Active Agents; D014867:Water