title: Nanosized emulsions stabilized by semisolid polymer interphase.
abstract: We introduce a new approach for stabilizing oil-in-water nanoemulsions using a semisolid interphase formed by the phase separation of amphiphilic block copolymers from the organic phase. This system is illustrated using an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL), with commonly used oils. PEO-b-PCL can be miscible with oil at elevated temperatures (70-80 degrees C); however, polymer/oil demixing occurs as the temperature drops below the melting temperature of PEO-b-PCL (approximately 55 degrees C). A homogeneous polymer/oil mixture was dispersed in water at 80 degrees C to generate embryonic emulsions, and then the emulsion size was reduced to a nanometer range through microfluidic homogenization. The structure of the generated nanoemulsions is irreversibly frozen as they are cooled down to ambient temperature. The nanoemulsions stabilized by PEO-b-PCL show the excellent colloidal stability against thermal and chemical stresses, exhibiting no significant changes in the size distribution during incubation for 4 months at ambient temperature or 10 days at 60 degrees C. This study demonstrates that PEO-b-PCL is an attractive emulsifying material for practical nanoemulsion formulations requiring structural stability under a broad range of conditions.
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. yoonsung@mit.edu
authors.forename: Yoon Sung
authors.initials: YS
authors.lastname: Nam
authors.forename: Jin-Woong
authors.initials: JW
authors.lastname: Kim
authors.forename: Jongwon
authors.initials: J
authors.lastname: Shim
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Han
authors.forename: Han Kon
authors.initials: HK
authors.lastname: Kim
mesh_terms: D004655:Emulsions / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*; D011091:Polyesters / Q000737:chemistry*
chemical_list: D004655:Emulsions; D011091:Polyesters; C458722:polyethylene oxide-polycaprolactone copolymer