title: Spatially Distributed Rheological Properties in Confined Polymers by Noncontact Shear.
abstract: When geometrically confined to the nanometer length scale, a condition in which a large portion of the material is in the nanoscale vicinity of interfaces, polymers can show astonishing changes in physical properties. In this investigation, we employ a unique noncontact capillary nanoshearing method to directly probe nanoresolved gradients in the rheological response of ultrathin polymer films as a function of temperature and stress. Results show that ultrathin polymer films, in response to an applied shear stress, exhibit a gradient in molecular mobility and viscosity that originates at the interfaces. We demonstrate, via molecular dynamics simulations, that these gradients in molecular mobility reflect gradients in the average segmental relaxation time and the glass-transition temperature.
authors.forename: Mithun
authors.identifier: http://orcid.org/0000-0002-2513-6006
authors.initials: M
authors.lastname: Chowdhury
authors.affiliation: University of Michigan - Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University , Shanghai 200240, P. R. China.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Guo
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Polymer Engineering, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Weston L
authors.initials: WL
authors.lastname: Merling
authors.affiliation: Department of Polymer Engineering, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Jayachandra H
authors.initials: JH
authors.lastname: Mangalara
authors.affiliation: Department of Polymer Engineering, University of Akron , Akron, Ohio 44325, United States.
authors.forename: David S
authors.identifier: http://orcid.org/0000-0002-1436-9269
authors.initials: DS
authors.lastname: Simmons
authors.forename: Rodney D
authors.identifier: http://orcid.org/0000-0001-6765-2933
authors.initials: RD
authors.lastname: Priestley