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Siegel der Universität
Department für Chemie - Arbeitsgruppe Prof. Strey

Polymer Nanofoams by Continuity Inversion of Dispersions

Lena Grassberger, 2013

 

Polymeric nanofoams promise excellent thermal insulation and interesting optical and mechanical properties. The Nanofoams by Continuity Inversion of Dispersions (NF-CID) procedure, invented by Strey and Müller [1], is one way for the synthesis of such nano-porous materials. In this work the voids of close-packed polymer nanoparticles were filled with super- or near critical CO2 at appropriate temperature and pressure. Above the glass transition temperature, the polymer showed an inversion to a highly viscous polymer matrix with superfluid inclusions. Pressure release led to both foaming and fixation of the matrix. Varying the concentration of a chain transfer agent, used in the particle synthesis, polymer foams with pore sizes between 200 nm and 2 µm and densities of 0.1-0.3 g cm-3 could be achieved. Furthermore, the influence of high pressure CO2 on colloidal crystals of polymer particles was investigated by time resolved small angle neutron scattering (SANS) experiments. In this context it turned out that the size of the nanoparticles varies with the CO2 pressure. At 70 bar the particles swelled with a halftime of 42 seconds from 27 to 35 nm. A compression to 150 bar resulted in a rapid increase by another 2 nm. Interestingly, the particles size was reduced only marginally by reduction to atmospheric pressure. It was shown that time resolved SANS experiments are very well suited to study the continuity inversion and the foaming process.