title: Magnetic and geometric anisotropy in particle-crosslinked ferrohydrogels.
abstract: Particle-crosslinked polymer composites and gels have recently been shown to possess novel or improved properties due to a covalent particle-matrix interaction. We employ spindle-like hematite particles as exclusive crosslinkers in poly(acrylamide) gels, and exploit their extraordinary magnetic properties for the realization of ferrohydrogels with a perpendicular orientation of the preferred magnetic and geometric axes of the particles. The angle-dependent magnetic properties of uniaxially oriented gels are investigated and interpreted with respect to particle-matrix interactions. The impact of the particle orientation on the resulting angle-dependent magnetic performance reveals the presence of two different contributions to the magnetization: a hysteretic component ascribed to immobilized particles, and a pseudo-superparamagnetic, non-hysteretic component due to residual particle mobility. Furthermore, a plastic reorientation of magnetic particles in the matrix when subjected to a transversal field component is observed.
authors.affiliation: Department Chemie, Institut für Physikalische Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany. annette.schmidt@uni-koeln.de.
authors.forename: Lisa
authors.initials: L
authors.lastname: Roeder
authors.forename: Philipp
authors.initials: P
authors.lastname: Bender
authors.forename: Matthias
authors.initials: M
authors.lastname: Kundt
authors.forename: Andreas
authors.initials: A
authors.lastname: Tschöpe
authors.forename: Annette M
authors.initials: AM
authors.lastname: Schmidt
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D016880:Anisotropy; D020100:Hydrogels / Q000737:chemistry*; D060328:Magnetic Phenomena; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D020100:Hydrogels; D058185:Magnetite Nanoparticles; D000099166:Polyacrylamides