TY  - JOUR
A1  - Spiekermann, Georg
A1  - Wilke, Max
A1  - Jahn, Sandro
T1  - Structural and dynamical properties of supercritical H2O-SiO2 fluids studied by ab initio molecular dynamics
JF  - Chemical geology : official journal of the European Association for Geochemistry
N2  - In this study we report the structure of supercritical H2O-SiO2 fluid composed of 50 mol% H2O and 50 mol% SiO2 at 3000 K and 2400 K. investigated by means of ab initio molecular dynamics of models comprising 192 and 96 atoms. The density is set constant to 138 g/cm(3), which yields a pressure of 4.3 GPa at 3000 K and 3.6 GPa at 2400 K. Throughout the trajec[ories, water molecules are formed and dissociated via the network modifying reaction 2 SiOH = SiOSi + H2O The calculation of the reaction constant K- [OH](2)/[H2O][O2-] is carried out on the basis of the experimentally relevant Q ' species notation and agrees well with an extrapolation of experimental data to 3000 K. After quench from 3000 K to 2400 K, the degree of polymerization of the silicate network in the 192-atom models increases noticeably within several tens of picoseconds, accompanied by release of molecular H2O. An unexpected opposite trend is observed in smaller 96-atom models, due to a finite size effect, as several uncorrelated models of 192 and 96 atoms indicate. The temperature-dependent slowing down of the H2O-silica interaction dynamics is described on the basis of the bond autocorrelation function. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Fluid
KW  - SiO2-H2O
KW  - SiO(2)Molecular dynamics
KW  - Polymerization
KW  - DFT
Y1  - 2016
U6  - https://doi.org/10.1016/j.chemgeo.2016.01.010
SN  - 0009-2541
SN  - 1878-5999
VL  - 426
SP  - 85
EP  - 94
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Yalcinkaya, Hacer
A1  - Bressel, Katharina
A1  - Lindner, Peter
A1  - Gradzielski, Michael
T1  - Controlled formation of vesicles with added styrene and their fixation by polymerization
JF  - Journal of colloid and interface science
N2  - Hypothesis: An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments: A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings: The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. (C) 2018 Elsevier Inc. All rights reserved.
KW  - Template reaction
KW  - Zwitterionic surfactant
KW  - Anionic surfactant
KW  - Styrene
KW  - Vesicle
KW  - Small angle neutron scattering
KW  - Polymerization
Y1  - 2018
U6  - https://doi.org/10.1016/j.jcis.2018.07.097
SN  - 0021-9797
SN  - 1095-7103
VL  - 531
SP  - 672
EP  - 680
PB  - Elsevier
CY  - San Diego
ER  -