title: Entropy-driven segregation of polymer-grafted nanoparticles under confinement.
abstract: The modification of nanoparticles with polymer ligands has emerged as a versatile approach to control the interactions and organization of nanoparticles in polymer nanocomposite materials. Besides their technological significance, polymer-grafted nanoparticle (PGNP) dispersions have attracted interest as model systems to understand the role of entropy as a driving force for microstructure formation. For instance, densely and sparsely grafted nanoparticles show distinct dispersion and assembly behaviors within polymer matrices due to the entropy variation associated with conformational changes in brush and matrix chains. Here we demonstrate how this entropy change can be harnessed to drive PGNPs into spatially organized domain structures on submicrometer scale within topographically patterned thin films. This selective segregation of PGNPs is induced by the conformational entropy penalty arising from local perturbations of grafted and matrix chains under confinement. The efficiency of this particle segregation process within patterned mesa-trench films can be tuned by changing the relative entropic confinement effects on grafted and matrix chains. The versatility of topographic patterning, combined with the compatibility with a wide range of nanoparticle and polymeric materials, renders SCPINS (soft-confinement pattern-induced nanoparticle segregation) an attractive method for fabricating nanostructured hybrid films with potential applications in nanomaterial-based technologies.
authors.affiliation: College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325.
authors.forename: Ren
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213.
authors.forename: Bongjoon
authors.initials: B
authors.lastname: Lee
authors.affiliation: Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Stafford
authors.affiliation: Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Jack F
authors.initials: JF
authors.lastname: Douglas
authors.affiliation: College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Dobrynin
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Bockstaller
authors.affiliation: College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325; alamgir@uakron.edu.
authors.forename: Alamgir
authors.identifier: 0000-0003-1302-9374
authors.initials: A
authors.lastname: Karim
keywords: confinement; entropy; polymer thin film; polymer-grafted nanoparticle; topographic pattern