TY  - JOUR
A1  - Haase, Martin F.
A1  - Grigoriev, Dmitry
A1  - Moehwald, Helmuth
A1  - Tiersch, Brigitte
A1  - Shchukin, Dmitry G.
T1  - Encapsulation of amphoteric substances in a pH-sensitive pickering emulsion
N2  - Oil-in-water (o/w) Pickering emulsions stabilized with silica nanoparticles were prepared. Droplets of diethyl phthalate (oil phase) act as reservoirs for 8-hydroxyquinoline (8-HQ), which is used as (a) the hydrophobizing agent for the silica particles and (b) an encapsulated corrosion inhibitor for application in active feedback coatings. The hydrophobization of silica nanoparticles with 8-HQ is determined by the amount of this agent adsorbed on the nanoparticle surface. The latter is governed by the 8-HQ concentration in the aqueous phase, which in turn depends on the degree of protonation and fir ally on the pH. We observe three ranges of 8-HQ adsorption value with respect to nanoparticle hydophobization: (I) insufficient, (2) sufficient, and (3) excessive adsorption by the formation of an 8-HQ bilayer, where only case 2 leads to the necessary nanoparticle hydrophobization. Hence emulsions stable in a narrow pH window between pH 5.5 and 4.4 follow. Here functional molecules are sufficiently charged to compensate for the charges on silica nanoparticles to make them interfacially active and thus able to stabilize an emulsion but they are still to a large extent uncharged and thereby remain in the oil phase. The emulsification is reversible upon changing the pH to a value beyond the stability region.
Y1  - 2010
UR  - http://pubs.acs.org/journal/jpccck
U6  - https://doi.org/10.1021/Jp104052s
SN  - 1932-7447
ER  - 
TY  - JOUR
A1  - Diehl, Christina
A1  - Cernoch, Peter
A1  - Zenke, Ingrid
A1  - Runge, Heike
A1  - Pitschke, Rona
A1  - Hartmann, Juergen
A1  - Tiersch, Brigitte
A1  - Schlaad, Helmut
T1  - Mechanistic study of the phase separation/crystallization process of poly(2-isopropyl-2-oxazoline) in hot water
N2  - The kinetics of the crystallization of thermoresponsive poly(2-isopropyl-2-oxazoline) in water and the time- dependent evolution of the morphology were examined using wide-angle X-ray scattering and conventional and cryogenic scanning electron microscopy. Results indicate that a temperature-induced phase separation produces a bicontinuous polymer network-like structure, which with the onset of crystallization collapses into individual particles (1-2 mu m in diameter) composed of a porous fiber mesh. Nanofibers then preferentially form at the particle surface, thus wrapping the microspheres like a ball of wool. The particle morphology is severely affected by changes in temperature and less by the initial polymer concentration.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/sm/index.asp
U6  - https://doi.org/10.1039/C0sm00114g
SN  - 1744-683X
ER  -