title: Pseudonegative thermal expansion and the state of water in graphene oxide layered assemblies.
abstract: Unraveling the complex interplay between thermal properties and hydration is a part of understanding the fundamental properties of many soft materials and very essential for many applications. Here we show that graphene oxide (GO) demonstrates a highly negative thermal expansion (NTE) coefficient owing to unique thermohydration processes related with fast transport of water between the GO sheets, the amphiphilic nature of nanochannels, and close-to-zero intrinsic thermal expansion of GO. The humidity-dependent NTE of GO layered assemblies, or "pseudonegative thermal expansion" (PNTE), differs from that of other hygroscopic materials due to its relatively fast and highly reversible expansion/contraction cycles and occurrence at low humidity levels while bearing similarities to classic NTE. Thermal expansion of polyvinyl alcohol/GO composites is easily tunable with additional intricacy of thermohydration effects. PNTE combined with isotropy, nontoxicity, and mechanical robustness is an asset for applications of actuators, sensors, MEMS devices, and memory materials and crucial for developing methods of thermal/photopatterning of GO devices.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor 48109, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhu
authors.forename: Christine M
authors.initials: CM
authors.lastname: Andres
authors.forename: Jiadi
authors.initials: J
authors.lastname: Xu
authors.forename: Ayyalusamy
authors.initials: A
authors.lastname: Ramamoorthy
authors.forename: Thomas
authors.initials: T
authors.lastname: Tsotsis
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Kotov
mesh_terms: D000327:Adsorption; D003460:Crystallization / Q000379:methods*; D006108:Graphite / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D016062:Porosity; D013499:Surface Properties; D013696:Temperature; D013814:Thermal Conductivity; D014867:Water / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D010087:Oxides; D014867:Water; D006108:Graphite