2012|13 Annual Report Fraunhofer IGB

86 CHEMISTRY Potential applications Open-pored polymer foams are interesting materials for nu- merous applications, especially as adsorber materials for sepa- ration or accumulation, as carriers for chemo- or biocatalysis, as well as three-dimensional carriers for mammalian cells or microorganisms. Conductive foams, formed by suitable ad- ditives, are even suitable as materials for electrodes for bio- fuel cells. For the named applications the inner surface of the pores must generally be equipped with functional groups or molecules. Depending on the pore structure and type of the polymer used for the foam, this is currently impossible or ex- tremely difﬁcult. New single-stage production We have developed a single-stage synthesis strategy for the simple production of macroporous polymer foams with func- tional groups that can easily be implemented using the so- called click reaction. An emulsion polymerization process (high internal phase emulsion) was used to produce a crosslinked polymer foam with azide functions for this. The organic phase contains the monomer, the crosslinker and a surfactant. The aqueous phase, which is placed into a reaction vessel together with the organic phase, contains the initiator for the radical polymeri- zation (Fig. 3). Foam with functional pores The end material shown as an example in Fig. 1 has a porosity of approx. 90 percent. The scanning electron microscope im- age in Fig. 2 shows the structure with open macropores in the range of approx. 5–10 μm and micropores below 1 μm. Azide functions react with alkyne functions (click reaction) un- der very mild conditions, such as biomolecules require for ex- ample, and without side reactions. We were able to show the binding of small molecules and polymers at the inner surface of the synthesized foam using an azide-alkyne cycloaddition (Fig. 4) in the examples of propargyl alcohol (Fig. 4A) and pro- pargyl-poly(methyl methacrylate) (Fig. 4B). Biocompatibility/biofunctionality In order for the material to be used as a cell carrier its biocom- patibility is a necessary prerequisite. Initial tests with human skin cells on the PMMA-modiﬁed foams showed, after incu- bation for 24 hours, improved cell adhesion in comparison to unmodiﬁed foam. Live/dead staining of the human cells that had been cultured at the surface for 24 hours, showed a high number of living cells. FUNCTIONAL POLYMER FOAMS Dr. rer. nat. Michaela Müller 1 2

2012|13 Annual Report Fraunhofer IGB

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