The goal of the project “Molecular dynamics simulation and experiments of complex polymers under flow and during mechanical recycling” is to better understand the behavior of complex branched polymers during processing and, in particular, during mechanical recycling—and thereby lay the groundwork for more recyclable plastic materials.

While linear polymers are well described in many models, branched structures such as comb, pompon, and star polymers exhibit significantly more complex viscoelastic and mechanical behavior. Their topology significantly influences how they flow under shear and strain, how they solidify—and how they degrade or undergo structural changes during recycling.Itispreciselythisrelationshipbetweenarchitecture, flowproperties, anddegradationprocessesthatiscrucialforreusingplasticsmultipletimeswithoutsignificantlydegradingtheirmaterialproperties.

Theprojectinvestigatesthebehaviorofcomplexpolymersatthemolecularlevelduringdeformationusingmoleculardynamicssimulations. Thesimulationsexaminetheresponsetostaticshearstress, oscillatingshearstress, anduniaxialstretching.The resulting viscoelastic properties are systematically compared with experimental rheological results and established models, providing valuable insights to advance polymer design and the recyclability of polymers. This allows for the identification of mechanisms that lead, for example, to hardening during stretching, altered shear relaxation, or undesirable molecular degradation during mechanical reprocessing.

In the long term, the insights gained are intended to be incorporated into the targeted molecular design of complex polymer structures, thereby making an important contribution to a circular plastics economy.

• Prof. Dr. Nina Merkert