Detailseite
Projekt
Auf Magnetfeld und Temperatur reagierende Hybridmaterialien mit rheologischer Kontrolle: Zusammenspiel von magnetischen Nanopartikeln und einem Gel-Netzwerk in AC, DC und AC+DC Feldern, gemessen mittels Hochfrequenz Kleinwinkelneutronenstreuung (SANS)
Antragsteller
Professor Dr. Michael Gradzielski
Fachliche Zuordnung
Physikalische Chemie von Molekülen, Flüssigkeiten und Grenzflächen, Biophysikalische Chemie
Strömungsmechanik
Strömungsmechanik
Förderung
Förderung von 2013 bis 2019
Projektkennung
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 238047398
Ferrohydrogels, with magnetic nanoparticles (MNPs) incorporated into a self-assembled gel matrix, will be studied as archetypal multi-scale responsive hybrid materials. The aim is to elucidate the interplay between MNP and the self-assembled network under AC and/or DC magnetic field to have controlled macroscopic rheology. So far low molecular weight hydrogelators were used that self-assemble via hydrophobic interaction and hydrogen bonds. MNPs are expected to locate at the network nodes via hydrophobic functionalization. For this we employ ferrite MNPs (Fe3O4, CoFe2O4, MnxZn1-xFe2O4) coated with silica, to provide biocompatibility and tunable surface charge to stabilize the dispersion and prevent chaining due to permanent dipole moments. The main tool is small angle neutron scattering (SANS), where AC and/or DC magnetic field will be applied. SANS is unique for such complex composite materials in that it probes the nanoscale (fibrils, locus of particles), also dynamically (transient structures, Néel and Brownian relaxations, using time-stamped neutrons, with 0.1 ms resolution; TISANE), extract individual components by selective nuclear contrast matching, and distinguish nuclear and magnetic domains using polarized neutrons. The outcome from SANS experiments will be correlated to rheological and magnetorheological data (macroscopic properties). The effect of particle incorporation on the gels will also be studied by light scattering, FCS, and X-ray photon correlation spectroscopy (XPCS). Cryo-TEM and AFM on selected samples will complement to obtain a full description of the hybrid materials. Parameters to be systematically varied in the hybrid systems are the stiffness of the fibrils, the adhesion strength at MNP/fibril junctions (tuned by choice of gelator and type of functionalization); the mesh size, density of nodes and number of junctions (controlled by concentrations of gelator and MNPs). Different results are expected based on the strength and number of junctions relative to the field strength and frequency, with rotation and locomotion of particles being allowed or inhibited. Local heating by MNP under AC field as well as thixotropic effects will be considered. One direction will be to develop gels which have a gelation temperature near ambient, to switch between fluid and gel state, so temperature can act as a stimulus and allows for fixing structure and property in an external magnetic field to retain structures, thereby leading to reversible memory features of shape and magnetic properties. Exploring the relevant parameter space correspondingly will then allow to correlate the unique mesoscopic structure information available from SANS with the matrix properties and thereby lead to a consistent description of the macroscopic properties. Such information is central to develop ferrogels for various applications of versatile magnetically responsive materials (such as actuators, artificial muscles, sensors etc.).
DFG-Verfahren
Schwerpunktprogramme
Internationaler Bezug
Frankreich
Mitverantwortlich
Sylvain Prevost, Ph.D.
