Polymer Physics

Polymer gels consist of a three dimensional network of crosslinked polymer chains which are swollen in a solvent; they are fascinating materials for applications as superabsorbers, matrixes in analytical chemistry or biology, or as storage and delivery systems for actives.  Classically, network junctions are formed by chemical bonds, ensuring great mechanical stability.  However, these chemical crosslinks are permanent, such that chemical gels cannot be processed or recycled.  Permanent chain interconnection is also detrimental for encapsulation and controlled release applications.  It is therefore desirable to use reversible gels, which is readily achieved by supramolecular chain crosslinking.  Previous work in this field has produced various types of such materials, primarily realized through chain interconnection by hydrogen bonding or transition metal complexation.  However, a comprehensive characterization and deep understanding between the chemical structure and the phenomenological behavior of these promising materials is still lacking.

Our research focuses on polymer networks that are crosslinked by supramolecular bonds.  We prepare, study, and process these networks in a systematic fashion.  For this purpose, we use a universal covalent precursor polymer and equip it with side groups that can be interconnected by non-covalent interactions such as hydrogen bonding or transition metal complexation.  This leads to networks that consist of the same basis material, yet exhibiting a strongly varying strength of chain interconnection.

We study these supramolecular gels to derive fundamental relations between the strength of non-covalent crosslinking and the network structure and dynamics, using methods such as macroscopic rheology as well as light, neutron, and x-ray scattering.  In addition, we use heterophase techniques such as miniemulsification and droplet-based microfluidics to fabricate supramolecular nano- and microgel particles.  These particles can serve as nano- and microcapsules for the encapsulation and controlled release of actives, including drugs, biopolymers, and living cells.  We also use these particles as microscopic probes to study their polymer network architectures, and we investigate the physical chemical properties of densely packed suspensions of these micro- and nanogels.

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