Polymer materials have made our life comfortable; they have also contributed to prolong it. One type of such materials are polymer networks and gels, and a particularly promising sub-type of these are active polymer gels. These are soft materials with adaptive action, whose function is based on non-covalent binding in the gel network, either in a sense of transient chain connectivity or in a sense of delicate interactions of the chains with their environment. Both modes of action can serve in various advanced applications in which a gel specimen serves to adapt its degree of swelling, its viscoelasticity, and its permeability in response to external parameters. To make this all truly useful, though, it is necessary to understand the mutual interplay between (nano)structure, dynamics, and properties of these fascinating materials.
This endeavor has been in our group’s focus for decades.
At the same time, our world witnessed increasing impacts of the most dangerous threat in mankind's history: the climate crisis.
Whereas polymer materials, including networks and gels, are stereotypes of the 20th century one-way economy that led into this crisis, they also have excellent promise to contribute to addressing our present climate and resource crises. There's two areas for that.
First, polymer gels have promise to help in adapting to climate-crisis consequences. For example, charged sensitive hydrogels that are active and switchable can serve to purify, detox, and desalinate water to ensure supply with this essential resource. Second, polymer-network materials that are interlinked non-covalently have prospect to be fully recyclable, thereby paving path to transform essentials such as rubbers and superabsorbers into a cyclic economy.
Our research is centered around these two areas. We target at the elementary understanding of the interplay of (nano)structure, dynamics, and properties of active and supramolecular polymer networks and gels such to develop material concepts for the two fields. With that, our work aims at contributing to make the 21st century the age in which mankind transformed its materials economy such to ensure a livable, lasting, and lovely planet.
In the first area of our current and prospective research, we're central and leading part of an international network of research groups from Mainz, Tehran, Bushehr, and Bagdad named 'HydroDeSal'. Our goal is to develop thermo-sensitive charged gels that can act as both draw-agents and semi-permeable membranes in forward osmosis processes, driven by the natural temperature oscillation of Earth's day-and-night cycle. Together with engineers from the Fraunhofer Institute for Microengineering and Microsystems, we target at developing a lab demonstrator setup that is able to purify and desalinate water from the Persian Gulf in amounts of some liters per day, which may then be industrially scaled up to actual application relevance for small villages at that sea.
Group picture of the HydroDeSal research network, taken in July 2023 during a general assembly in Mainz
Schematic of our approach for seawater desalination with thermo-sensitive and charged hydrogels
In the second area of our current and prospective research, we aim to employ clustering of non-covalent junctions in supramolecular polymer networks to serve as strong reinforcement. This effect makes the networks as stable as covalently-jointed ones, but as their crosslinking is still non-covalent, they can still be decomposed and thereby recycled. Our initial research focus is on networks in the melt and gel state, with a specific view to conceptually and quantitatively understand the interplay of supramolecular and macromolecular dynamics in further interplay with junction clustering, and how that translates into mechanical properties, specifically into mechanical spectra.
Cover pictures on the effect of junction spatial arrangement and clustering on transient polymer-network dynamics and mechanics
In further collaborative research, our group is a central and leading part (spokespersonship) of two DFG-funded coordinated networks: the Research Unit FOR 2811 and the Collaborative Research Center SFB 1552. In the first, we use light scattering, confocal microscopy, and rhology to unravel structure-property relations of amphiphilic polymer co-networks, with a special view on the interplay of structural inhomogeneity imparted during the process of network conneciton and in momentary states of swelling. In the second, we use similar methods to quantify the effect of connectifity defects in metallo-supramolecular transient networks with model-type structure. Both these areas of research are central in their respective coordinated environments; they also deliver crucial knowledge to our application-oriented research on polymer-materials for a cyclic economy and for climate-change adaption.
R. von Klitzing, TU Darmstadt
Mechanics of Inhomogeneous Polymer Gels
ACS Macro Lett. 2015, 4, 698–703.
Macromol. Chem. Phys. 2023, 225, 2300389.
K. Saalwächter, Halle University
Structure and Defects in Sensitive Polymer Gels
Macromolecules 2022, 55, 6573–6589.
Macromolecules 2022, 55, 5997–6014.
Soft Matter 2022, 18, 1071–1081.
Chem. Mater. 2023, 35, 4026–4037.
B. D. Olsen, Massachusetts Institute of Technology
Chain Dynamics in Supramolecular Polymer Gels
Macromolecules 2016, 49, 5599–5608.
Phys. Chem. Chem. Phys. 2022, 24, 4859–4870.
Recent and Current Industry Projects
Siemens AG, Berlin, Germany
Polymer-Based Engine Insulators
Procter & Gamble Germany GmbH & Co Operations oHG, Schwalbach, Germany
BASF SE, Ludwigshafen, Germany
Microgel Additives for Care Products