Magnetic Particle Nanorheology is a versatile tool to investigate the size-dependent rheological ... more Magnetic Particle Nanorheology is a versatile tool to investigate the size-dependent rheological properties of complex fluids using magnetic tracer particles.
A promising route for the fabrication of ferronematic phases is the attachment of a LC polymer sh... more A promising route for the fabrication of ferronematic phases is the attachment of a LC polymer shell onto the surface of nanoparticles. Here, we extend this approach to ferronematic phases based on superparamagnetic particles in a 5CB matrix.
The implementation of anisotropy to functional materials is a key step towards future smart mater... more The implementation of anisotropy to functional materials is a key step towards future smart materials.
A systematic survey on magnetic particle nanorheology on polymer solutions using different partic... more A systematic survey on magnetic particle nanorheology on polymer solutions using different particle sizes and geometries, and different driving modes.
The incorporation of nanoparticles into soft matrices opens a broad spectrum of novel property co... more The incorporation of nanoparticles into soft matrices opens a broad spectrum of novel property combinations. However, one of the major challenges for these systems remains the compatibilization of particles with the surrounding matrix by proper surface functionalization. For silicon-based systems or liquid crystalline phases, polydimethylsiloxane (PDMS) brushes at the surface of particles increase the stability against particle agglomeration in such systems. Here, we report a novel approach for the functionalization of particles with a polysiloxane brush by surface-initiated ring-opening polymerization of a cyclosiloxane. For this purpose, surface hydroxy groups of silica and silica-coated hematite particles are used as initiators in combination with phosphazene bases as catalysts. The ring–chain equilibrium of a model-based solution polymerization is investigated in detail to find the appropriate reaction parameters. The corresponding molar masses are determined and compared by 1H-...
The journal of physical chemistry. B, Jan 10, 2015
The present paper addresses the loading of thermoresponsive poly-N-isopropylacrylamide (PNIPAM) b... more The present paper addresses the loading of thermoresponsive poly-N-isopropylacrylamide (PNIPAM) based microgel particles with magnetic nanoparticles (MNP: CoFe2O4@PAA (PAA = poly(acrylic acid))) and their response to an external magnetic field. The MNP uptake is analyzed by transmission electron microscopy (TEM). Obviously, the charge combination of MNP and microgels plays an important role for the MNP uptake, but it does not explain the whole uptake process. The MNP uptake results in changes of size and electrophoretic mobility, which is investigated by dynamic light scattering (DLS) and a Zetasizer. The microgels loaded with MNP preserve their thermosensitivity, and they show magnetic separability and are considered as magnetic microgels. After adsorption at a surface the magnetic microgels are studied with a scanning force microscope and indentation experiments. The magnetic microgels show an elongation along the magnetic field parallel to the surface while the height of the micr...
Magnetic Particle Nanorheology is a versatile tool to investigate the size-dependent rheological ... more Magnetic Particle Nanorheology is a versatile tool to investigate the size-dependent rheological properties of complex fluids using magnetic tracer particles.
A promising route for the fabrication of ferronematic phases is the attachment of a LC polymer sh... more A promising route for the fabrication of ferronematic phases is the attachment of a LC polymer shell onto the surface of nanoparticles. Here, we extend this approach to ferronematic phases based on superparamagnetic particles in a 5CB matrix.
The implementation of anisotropy to functional materials is a key step towards future smart mater... more The implementation of anisotropy to functional materials is a key step towards future smart materials.
A systematic survey on magnetic particle nanorheology on polymer solutions using different partic... more A systematic survey on magnetic particle nanorheology on polymer solutions using different particle sizes and geometries, and different driving modes.
The incorporation of nanoparticles into soft matrices opens a broad spectrum of novel property co... more The incorporation of nanoparticles into soft matrices opens a broad spectrum of novel property combinations. However, one of the major challenges for these systems remains the compatibilization of particles with the surrounding matrix by proper surface functionalization. For silicon-based systems or liquid crystalline phases, polydimethylsiloxane (PDMS) brushes at the surface of particles increase the stability against particle agglomeration in such systems. Here, we report a novel approach for the functionalization of particles with a polysiloxane brush by surface-initiated ring-opening polymerization of a cyclosiloxane. For this purpose, surface hydroxy groups of silica and silica-coated hematite particles are used as initiators in combination with phosphazene bases as catalysts. The ring–chain equilibrium of a model-based solution polymerization is investigated in detail to find the appropriate reaction parameters. The corresponding molar masses are determined and compared by 1H-...
The journal of physical chemistry. B, Jan 10, 2015
The present paper addresses the loading of thermoresponsive poly-N-isopropylacrylamide (PNIPAM) b... more The present paper addresses the loading of thermoresponsive poly-N-isopropylacrylamide (PNIPAM) based microgel particles with magnetic nanoparticles (MNP: CoFe2O4@PAA (PAA = poly(acrylic acid))) and their response to an external magnetic field. The MNP uptake is analyzed by transmission electron microscopy (TEM). Obviously, the charge combination of MNP and microgels plays an important role for the MNP uptake, but it does not explain the whole uptake process. The MNP uptake results in changes of size and electrophoretic mobility, which is investigated by dynamic light scattering (DLS) and a Zetasizer. The microgels loaded with MNP preserve their thermosensitivity, and they show magnetic separability and are considered as magnetic microgels. After adsorption at a surface the magnetic microgels are studied with a scanning force microscope and indentation experiments. The magnetic microgels show an elongation along the magnetic field parallel to the surface while the height of the micr...
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Papers by Annette Schmidt