title: Wetting-Dewetting and Dispersion-Aggregation Transitions Are Distinct for Polymer Grafted Nanoparticles in Chemically Dissimilar Polymer Matrix.
abstract: Simulations and experiments are conducted on mixtures containing polymer grafted nanoparticles in a chemically distinct polymer matrix, where the graft and matrix polymers exhibit attractive enthalpic interactions at low temperatures that become progressively repulsive as temperature is increased. Both coarse-grained molecular dynamics simulations, and X-ray scattering and neutron scattering experiments with deuterated polystyrene (dPS) grafted silica and poly(vinyl methyl ether) PVME matrix show that the sharp phase transition from (mixed) dispersed to (demixed) aggregated morphologies due to the increasingly repulsive effective interactions between the blend components is distinct from the continuous wetting-dewetting transition. Strikingly, this is unlike the extensively studied chemically identical graft-matrix composites, where the two transitions have been considered to be synonymous, and is also unlike the free (ungrafted) blends of the same graft and matrix homopolymers, where the wetting-dewetting is a sharp transition coinciding with the macrophase separation.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States.|Department of Chemical and Biomolecular Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Martin
authors.affiliation: Department of Materials Engineering, University of Houston , Houston, Texas 77004, United States.
authors.forename: Katrina Irene S
authors.initials: KI
authors.lastname: Mongcopa
authors.affiliation: National Institute of Standards and Technology Center for Neutron Research , Gaithersburg, Maryland 20899, United States.|Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Rana
authors.initials: R
authors.lastname: Ashkar
authors.affiliation: National Institute of Standards and Technology Center for Neutron Research , Gaithersburg, Maryland 20899, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Butler
authors.affiliation: Department of Chemical and Biomolecular Engineering, Department of Petroleum Engineering, Department of Chemistry, University of Houston , Houston, Texas 77004, United States.
authors.forename: Ramanan
authors.initials: R
authors.lastname: Krishnamoorti
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Delaware , Newark, Delaware 19716, United States.|Department of Materials Science and Engineering, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Arthi
authors.initials: A
authors.lastname: Jayaraman