Connectivity Defects in Metallo-Supramolecular Polymer Networks at Different Self-Sorting Regimes

The properties of polymer networksdepend on their connectivity,specifically on the presence of connectivity defects like loops anddangling ends. While chemically crosslinked networks have a frozendistribution of defects on multiple length scales, equivalent transientones are capable of self-repairing. To study this potential, we employspatial hindrance as an effective self-sorting mechanism to developmetallo-supramolecular polymer networks based on heteroleptic complexes.We functionalize tetra-arm poly-(ethylene glycol) (tetraPEG) chainswith the mesitylene-substituted phenanthroline ligand, which is incapableof homoleptic complexation, yet it can form heteroleptic complexeswith tetraPEG precursors functionalized with unsubstituted phenanthrolineor terpyridine ligands. This way, the formation of primary loops canbe avoided upon selective formation of heteroleptic complexes. Nevertheless,the coordination geometry preference of the utilized metal ion cantune the extent of self-sorting and consequently the network structureand defect composition. The latter is pursued via MQ-NMR, and periodicdensity functional theory simulations are used to visualize the structureand explain its relationship with the dynamics as measured by rheology.Our results demonstrate that Cu-(I) can inherently adopt the geometryrequirements of both desired heteroleptic complexes by benefitingfrom the & pi;-stabilization effect, thereby creating a networkwith the least primary loops and dangling ends.

Automated summary

The properties of polymer networks are influenced by the presence of connectivity defects like loops and dangling ends. Transient polymer networks based on metallo-supramolecular polymer networks and hindrance can self-sort to develop networks with fewer defects. By using heteroleptic complexes and adjusting the coordination geometry preference, we can control the self-sorting process and reduce the formation of primary loops and dangling ends. Our results show that copper(I) can adopt the desired geometry requirements and create a network with the least number of defects.