title: Reversible Thermal Stiffening in Polymer Nanocomposites.
abstract: Miscible polymer blends with different glass transition temperatures (Tg) are known to create confined interphases between glassy and mobile chains. Here, we show that nanoparticles adsorbed with a high-Tg polymer, poly(methyl methacrylate), and dispersed in a low-Tg matrix polymer, poly(ethylene oxide), exhibit a liquid-to-solid transition at temperatures above Tg's of both polymers. The mechanical adaptivity of nanocomposites to temperature underlies the existence of dynamically asymmetric bound layers on nanoparticles and more importantly reveals their impact on macroscopic mechanical response of composites. The unusual reversible stiffening behavior sets these materials apart from conventional polymer composites that soften upon heating. The presented stiffening mechanism in polymer nanocomposites can be used in applications for flexible electronics or mechanically induced actuators responding to environmental changes like temperature or magnetic fields.
authors.affiliation: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Erkan
authors.initials: E
authors.lastname: Senses
authors.affiliation: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Andrew
authors.initials: A
authors.lastname: Isherwood
authors.affiliation: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Pinar
authors.initials: P
authors.lastname: Akcora
keywords: adaptive; confinement; dynamic coupling; interphase; miscible blend; polymer nanocomposite; reversible stiffening