title: Nanoscale Motion of Soft Nanoparticles in Unentangled and Entangled Polymer Matrices.
abstract: We have studied the motion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles modified with poly(ethylene glycol) (PEG) arms immersed in PEG matrices of different molecular weight. Employing neutron spin echo spectroscopy in combination with pulsed field gradient (PFG) NMR we found the following. (i) For entangled matrices the center of mass mean square displacement (MSD) of the PEG-POSS particles is subdiffusive following a t^{0.56} power law. (ii) The diffusion coefficient as well as the crossover to Fickian diffusion is independent of the matrix molecular weight and takes place as soon as the center of mass has moved a distance corresponding to the particle radius-this holds also for unentangled hosts. (iii) For the entangled matrices Rubinstein's scaling theory is validated; however, the numbers indicate that beyond Rouse friction the entanglement constraints appear to strongly increase the effective friction even on the nanoparticle length scale imposing a caveat on the interpretation of microrheological experiments. (iv) The oligomer decorated PEG-POSS particles exhibit the dynamics of a Gaussian star with an internal viscosity that rises with an increase of the host molecular weight.
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Lungova
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Krutyeva
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Pyckhout-Hintzen
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Wischnewski
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Monkenbusch
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Allgaier
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ohl
authors.affiliation: Institute Laue Langevin (ILL), 38000 Grenoble, France and European Spallation Source (ESS), 22363 Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Sharp
authors.affiliation: Jülich Centre for Neutron Science (JCNS) & Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Richter