Steric stabilization of core-shell nanoparticles in liquid carbon dioxide at the vapor pressure.
Nondilute nanoparticle dispersions were stabilized in liquid CO2 at 25 degrees C at pressures as low as the vapor pressure for greater than 30 min. By modifying hydrophilic silica with a trifunctional silylating agent, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxy silane, a cross-linked polymer shell was formed around the silica core. The presence of the shell led to weaker Hamaker interactions between approaching fluoro-silica composite particles and enabled dispersibility at weaker solvent conditions (low pressures) than for metals with larger Hamaker constants. Steric stabilization of the nanoparticles was provided by low-molecular-weight perfluorodecane side chains at the surface of the fluoro-silica composite shell. Compared to polymeric chains, the perfluorodecane side chains are more easily solvated and thus stabilize nanoparticle dispersions in CO2 at much lower pressures, even down to the vapor pressure.
Dickson
Jasper L
JL
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
Shah
Parag S
PS
Binks
Bernard P
BP
Johnston
Keith P
KP
D002245:Carbon Dioxide / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry*; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011312:Pressure; D012821:Silanes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014835:Volatilization
C509679:(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxy silane; D005466:Fluorocarbons; D012821:Silanes; D002245:Carbon Dioxide; D012822:Silicon Dioxide