title: Polystyrene colloidal crystals: Interface controlled thermal conductivity in an open-porous mesoparticle superstructure.
abstract: Colloidal crystals typically consist of sub-micron sized monodisperse particles, which are densely packed on a face centered cubic lattice. While many properties of this material class have been studied over the past decades, little is known about their thermal transport properties. The high amount of interfaces and their small interparticle contact area should result in efficient thermal insulation. Using laser flash analysis we report for the first time on the temperature dependent thermal conductivity of a freestanding 366 nm polystyrene (PS) colloidal crystal. Macroscopic monoliths of these samples were fabricated by colloidal self-assembly. We demonstrate a very low thermal conductivity κ of 51 mW K(-1) m(-1) (κ of bulk PS∼140 mW K(-1) m(-1)). Remarkably, this low thermal conductivity is reached at a comparatively high density of 750 kg m(-3). It can be further increased by almost 300% upon film formation and loss of the colloidal mesostructure. Additionally, this open porous structure is largely independent of the surrounding atmosphere. This can be rationalized by the small size (∼100 nm) of the pores present within this colloidal crystal.
authors.affiliation: University of Bayreuth, Physical Chemistry 1 - Polymer Systems, Universitaetsstr. 30, 95447 Bayreuth, Germany.
authors.forename: Fabian A
authors.initials: FA
authors.lastname: Nutz
authors.affiliation: University of Bayreuth, Physical Chemistry 1 - Polymer Systems, Universitaetsstr. 30, 95447 Bayreuth, Germany.
authors.forename: Pia
authors.initials: P
authors.lastname: Ruckdeschel
authors.affiliation: University of Bayreuth, Physical Chemistry 1 - Polymer Systems, Universitaetsstr. 30, 95447 Bayreuth, Germany. Electronic address: markus.retsch@uni-bayreuth.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Retsch
keywords: Colloidal crystal; Porous film; Thermal boundary resistance; Thermal conductivity; Thermal switch