Finetuning the Properties of Styrene-Based Porous Polymers via Emulsion Templating

Porous materials via templating routes


Porous polymers are solid foams that can be found everywhere in modern life as they can be used as isolation and packaging materials. When synthesized in the conventional way, one obtains polydisperse solid foams whose structural properties such as pore size, shape, and connectivity are difficult to adjust. Monodispersity, on the other hand, leads to a rather comfortable control of structure-property-relationships and can be achieved via a monodisperse template. The method of choice in this project is to form a monodisperse high internal phase emulsion (HIPE) with the help of microfluidics. The dispersed phase is water with a volume fraction around 75%, while the continuous phase contains the monomer styrene, the cross-linker divinylbenzene, and the technical surfactant Hypermer 2296. In previous studies it was found that the final product changes from an open-cell, spherical foam with porous pore walls (see Figure 1, bottom) to a closed-cell, honeycomb-like foam with granular pore surfaces (see Figure 1, top) when the thermic initiator is changed from the oil-soluble azobisisobutyronitrile (AIBN) to the water-soluble potassium peroxydisulfate (KPS) [1]. Even though hypotheses exist for how the overall [2,3] as well as the fine structure [4] form, quantitative evidence for these hypotheses is still missing. The goal of this project is (a) to provide quantitative evidence for the experimental observations, (b) to further investigate structure-property-relationships, and (c) to transfer the knowledge to another monomer/cross-linker system. After synthesizing the emulsion templates with a microfluidic chip, the polymerized foams will be analyzed as regards their structural and mechanical properties.

Figure 1 SEM (scanning electron microscope) pictures of polystyrene foams synthesized from monodisperse emulsion templates with (top) potassium peroxydisulfate (KPS) or (bottom) azobisisobutyronitrile (AIBN) [4]).
[1] Monodisperse Emulsions as Template for Highly Structured Polymer Foams, A. Quell, PhD Thesis, University of Stuttgart, 2016.
[2] On How the Locus of Initiation Influences the Morphology and the Pore Connectivity of a Monodisperse Polymer Foam, A. Quell, B. de Bergolis, W. Drenckhan, C. Stubenrauch, Macromolecules, 2016, 49,5059-5067.
[3] Creating honeycomb structures in porous polymers by osmotic transport, A. Quell, S. Heitkam, W. Drenckhan, C. Stubenrauch, ChemPhysChem, 2017, 18,451-454.
[4] Diving into the finestructure of macroporous polymer foams synthesised via emulsion templating: a phase diagram study, A. Quell, T. Sottmann, C. Stubenrauch, Langmuir, 2017, 33, 537-542.


This picture showsCosima Stubenrauch
Prof. Dr.

Cosima Stubenrauch

Dean of Faculty

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