Bio-inspired Processing of Polyelectrolyte Complexes

Polymer processing deals with converting polymer building blocks into final products via chemical reactions, shaping or compounding. Despite their key importance in achieving the required material properties, existing methods provide only limited control over the structure of the material. In contrast, the level of control that biological organisms exercise over the structure of the materials they fabricate is remarkable and unmatched. The extraordinary material properties (the threads produced by velvet worms are remarkably sticky and stiff; the beak of a jumbo squid is extremely hard; and spider silk is incredibly tough) found in these natural systems have been of interest to researchers for a long time.

Recent breakthroughs indicate that coacervation may play a key role in the processing of many natural materials. Coacervates are concentrated macromolecular phases that form upon phase separation. An understanding is emerging that liquid coacervate phases enable aqueous processing of materials and that gradual changes in solubility in space and time lead to controlled solidification.

We work on the development of polymer processing strategies by mimicking this natural process. Previously, we developed bio-inspired coacervate-based adhesives with well-controlled architectures and compositions. For a given polyelectrolyte couple, depending on the salt concentration of the medium, a complex coacervate either behaves as a free-flowing viscoelastic fluid or a rigid polyelectrolyte complex solid or anything in between. This outstanding versatility has made polyelectrolyte complexes good candidates for a wide range of adhesive applications.

Currently we are using microfluidic technology to enable gradual solidification. This enables us to control the dynamic process of phase separation in space and time by gradually changing the local environment (pH, ionic strength and crowding). This will lead to the supramolecular assembly of the materials. Moreover, recent developments in microfluidic 3D printing will enable fabrication of large structures with unprecedented control of material composition.