Linker Molar Mass-Driven Control over Supramolecular Network Relaxation and Architecture in BTA Hydrogels.

The fibrous, viscoelastic extracellular matrix (ECM) directs cell fate through mechanotransduction, but recreating these time-dependent mechanics in biomaterials remains a significant challenge. Current synthetic matrices rarely reconcile fibrillar architecture, physiological stiffness, and stress relaxation, with most systems achieving only some of these hallmarks. Supramolecular benzene-1,3,5-tricarboxamide (BTA) hydrogels offer a compelling route forward, as their hydrogen-bonded nanofibers mimic ECM-like networks. Simultaneously, the reversible dynamic hydrogen bonding responsible for the assemblies enables shear thinning, self-healing, and tunable viscoelasticity. Here, three distinct BTA hydrogels were developed, distinguishable by the hydrophilic poly-(ethylene) glycol (PEG) linker length, and all hydrogelators self-assemble and form self-healing, shear thinning hydrogels. Curiously, in contrast to covalent networks, shortening the length of PEG leads to a decrease in stiffness (G') and faster stress relaxation time scales (t 1/2). Blending BTA hydrogelators with two different molar masses leads to an almost linear increase in G' yet a more modest increase in t 1/2. The hydrogels were 3D printed with good shape fidelity, and all three hydrogels are adherent, leading to a self-sustaining construct composed of three regions with distinct G' and t 1/2. These findings emphasize the power of using polymer length as an orthogonal design handle, further expanding our chemical toolbox for developing processable biomaterials with tunable viscoelasticity.