Controlled, supramolecular polymer formulation to engineer hydrogels with tunable mechanical and dynamic properties

Nature uses combined covalent (chemical bonds) and non-covalent (physical bonds) synthesis in a highly, controlled multi-step fashion to create functional materials with different mechanical and dynamic properties out of similar building blocks. Surprisingly, this control in fully synthetic systems remains elusive, even though the effects of formulation pathways on the assembly processes have been emphasized—highlighting the importance of and relationship between energy landscapes and function in synthetic systems. Here, we control multiple, coherent supramolecular assembly processes (fiber formation and crosslinking) to formulate hydrogels with tunable mechanical and dynamic properties. Hydrogels are prepared via two different formulation methods using similar building blocks (monofunctional and bifunctional supramolecular monomers), including (1) the mixing of the supramolecular monomers under basic conditions (F_basic) and (2) the mixing of the supramolecular monomers under neutral conditions (F_neutral). In F_basic, network formation is induced via simultaneous fiber formation and crosslinking, yielding homogeneously mixed networks which are dense, stiff (~10 kPa) and robust. In F_neutral, network formation is induced through sequential fiber formation and crosslinking, yielding heterogenous, soft (~2 kPa) and dynamic networks. With these results, we advance towards the controlled, multistep, non-covalent synthesis to create larger hierarchical, functional structures, similar to nature.