17th November 2017

High-performance polymers (HPPs)

High-performance polymers (HPPs) are polymer materials of outstanding chemical resistivity, i.e. resistance against numerous chemicals, thermal stability, and mechanical performance. Hence they are found in applications in the aeronautics and automotive sectors, or e.g. as low-weight insulating materials in electronic components. The properties of HPPs are a direct consequence of their molecular structure: their monomeric units bear aromatic and/or heteroaromatic moieties or rather rigid and partially delocalized moieties such as amide or imide functions. These structural features generate stiff macromolecules that are pretty different from chain-flexible polymer such as poly(ethylene): HPPs often show Tg values of several hundred ˚C, or even none at all.

Unfortunately, the properties of HPPs come at a high cost: conventional syntheses involve high-boiling, toxic and expensive solvents and catalysts, long reaction times and high reaction temperatures of up to 500 ˚C. We are working on the development of non-classical polymer syntheses for HPPs. Recently, we developed hydrothermal polymerization (HTP), a green technique that yield polyimides in nothing but hot water at autogenous pressure.[1-5] Most interestingly, HTP allows for obtaining polyimides of unprecedented crystallinity. Since crystallinity is a highly desired feature for HPPs, HTP is not only benign, but in addition allows for improving the HPP properties. Another non-classical technique we work on are solid-state polycondensations (SSPs). Here, the co-monomers are pre-organized in a crystal (typically an organic salt) in the solid-state. These monomer salts can then be converted to polymers by simply applying heat, without the need for solvents or catalysts.[6] For polyimides, the crystallinity obtained by SSP cannot match that obtained via HTP. However polyimides from SSP show other property improvements, such as gas selectivity,[7] or retention of the initial monomer crystal shape.[6]

Read more about hydrothermal and solid-state polymerizations, and about why crystallinity is a desired feature for HPPs.

References:

[1] B. Baumgartner, M. J. Bojdys and M. M. Unterlass*, Polym. Chem. 20145, 3771-3776. “Geomimetics for Green Polymer Synthesis: Highly Ordered Polyimides via Hydrothermal Techniques

[2] B. Baumgartner, M. Puchberger, M. M. Unterlass*, Polym. Chem. 20156, 5773-5781. “Towards a General Understanding of Hydrothermal Polymerization of Polyimides

[3] M. M. Unterlass*, Mater. Today 201518, 242-243. “Creating geomimetic polymers

[4] B. Baumgartner, M. J. Bojdys, P. Skrinjar and M. M. Unterlass*, Macromol. Chem. Phys. 2016, in press. DOI: 10.1002/macp.201500287. “Design Strategies in Hydrothermal Polymerization of Polyimides

[5] M. M. Unterlass*, Eur. J. Inorg. Chem. 2016in press. DOI: 10.1002/ejic.201501130. “Green Synthesis of Inorganic-Organic Hybrid Materials: State of the Art and Future Perspectives

[6] K. Kriechbaum, D. A. Cerrón-Infantes, B. Stöger and M. M. Unterlass*, Macromolecules 201548, 8773-8780. “Shape-Anisotropic Polyimide Particles by Solid-State Polycondensation of Monomer Salt Single Crystals

[7] M. M. Unterlass*, F. Emmerling, M. Antonietti, J. Weber, Chem. Commun. 201450, 430-432. “From dense monomer salt crystals to CO2 selective microporous polyimides via solid-state polymerization