A) Macromolecular Colloquium, Freiburg, Germany (February 15-17, 2017)
The Macromolecular Journals sponsored two prizes for the best poster presentations. The prizes were awarded to:
a1) Reversible Transition between Anisotropic and Isotropic Thermal Transport in Polyurethane Foams
Bernd A. F. Kopera,* 1 Markus Retsch,1 Mokit Chau,2 Vanessa R. Machado,2 S. Mastour Tehrani,2 M. A. Winnik,2 E. Kumacheva 2
1 Physical Chemistry – Polymer Systems, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany; Email: [email protected]
2 Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
Polyurethane foams are well established thermal insulators and find commercial application as insulating foams. However, control over the thermal transport properties in different directions is hard to achieve with isotropic foams but imperative for future dynamic insulation materials. Here, we demonstrate elastic polyurethane foams with anisotropic lamellar microstructure formed by freeze-casting of water based polyurethane dispersions (Figure 1). Freeze-casting is an emerging technology used to create freestanding foams with anisotropic structure and properties. This anisotropy results in orientation-dependent mechanical and thermal transport properties. Most importantly, the thermal conductivity and thermal diffusivity can be reversibly transitioned between an anisotropic and an isotropic state. This transition is achieved by altering the thermal conductivity and diffusivity of the surrounding atmosphere either by changing the pressure of the gas or its composition.
Figure 1. Left: Micro computed tomography showing the anisotropic porous structure of the PU-foams. Middle: Thermal conductivity of the PU-foam as a function of helium pressure, parallel and perpendicular to the direction of ice growth. Right: Reversible transition between isotropic and anisotropic thermal conductivity over several cycles from vacuum to helium and back.
 B. P. Jelle, Energy and Buildings 2011, 43, 2549.
 B. Wicklein, A. K., G. Salazar-Alvarez, F. Carosio, G. Camino, M. Antonietti, L. Bergstrom, Nature nanotechnology 2015, 10, 277.
a2) Let’s Get Things in Order: Sequence Controlled Anionic Polymerization of Aziridines
Elisabeth Rieger,* Tassilo Gleede, Angelika Manhart, Laura Thomi, Manfred Wagner, Frederik R. Wurm
Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany; Email:[email protected]
We recently started the investigation of the anionic polymerization of aziridines: the poster summarizes our efforts to establish sulfonamide-activated aziridines as a novel monomer family, with different (functional) groups, for the living anionic polymerization. A systematic investigation of the polymerization kinetics is represented to determine the influence of different solvents and counter ions, monitored in-situ by 1H NMR-spectroscopy. The poster illustrates the simultaneous copolymerization of up to five competing monomers in an one-pot approach, examined by real-time 1H NMR spectroscopy. The monomer sequence is gracefully adjusted by the monomer reactivity, related to the electron-withdrawing effect of the sulfonamide groups. This allows us for the first time to mix different monomers and control their incorporation in a copolymer with structures, ranging from random over gradient to block-like composed copolymers. We believe that the anionic polymerization of aziridines will provide straightforward access to novel polyamides and –amines with interesting properties for a lot of applications.