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Soft, conformally shaped thermoplastic elastomer (TPE) hydrogels producible from a moldable precursor material are desirable in many biomedical, surgical, and pharmaceutical applications. An innovative class of hydrogel networks was developed by employing photocurable, moldable solutions of melt-assembled spherical micelles formed from ω-anthracenylpolystyrene-b-poly(ethylene oxide) diblock copolymer. Photoinduced [4 + 4] cycloaddition (λ = 365 nm) of terminal anthracene groups populating the hydrophilic corona of each micelle was used to produce polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymer tethers or network strands among adjacent micelles. Structural uniformity in the micelle population was confirmed by small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS). Homogeneous dispersal of the assembled micelle building blocks in water resulted in spreadable or moldable photoactive micelle solutions, studied for their stability in solution and ability to rapidly form elastomeric hydrogels once irradiated. Once in molds, these solutions of varied concentration were irradiated to form soft TPE hydrogels with dynamic shear modulus controllable with irradiation time (triblock copolymer content), exhibiting prescribed shape consistent with high-fidelity conformal fill.

Supramolecular polymers are known to form strong and resilient hydrogels which can take up large amounts of water while exhibiting ease of processing and self-healing. They also possess similarities with networks of biological macromolecules. The combination of these features makes supramolecular polymers ideal candidates for studying mechanisms and consequences of self-assembly, which are relevant to biological materials. At the same time, this renders investigations of mixed hydrogels based on different supramolecular compounds necessary, since this substantially widens their applicability. Here, we address unusual viscoelastic properties of a class of binary hydrogels made by mixing fibrillar supramolecular polymers that are formed from two compounds: 1,3,5-benzene-tricarboxamide decorated with aliphatic chains terminated by tetra(ethylene glycol) (BTA) and a 20 kg/mol telechelic poly(ethylene glycol) decorated with the same hydrogen bonding BTA motif on both ends (BTA-PEG-BTA). Using a suite of experimental and simulation techniques, we find that the respective single-compound-based supramolecular systems form very different networks which exhibit drastically different rheology. More strikingly, mixing the compounds results in a non-monotonic dependence of modulus and viscosity on composition, suggesting a competition between interactions of the two compounds, which can then be used to fine-tune the mechanical properties. Simulations offer insight into the nature of this competition and their remarkable qualitative agreement with the experimental results is promising for the design of mixed hydrogels with desired and tunable properties. Their combination with a sensitive dynamic probe (here rheology) offer a powerful toolbox to explore the unique properties of binary hydrogel mixtures., A two-component hydrogel system, comprising two different supramolecular molecules based on the same hydrogen bonding motif, is shown to exhibit a non-monotonic dependence of modulus and viscosity on composition. This binary hydrogel consists of fibrillar supramolecular polymers formed from two compounds, 1,3,5-benzene-tricarboxamide decorated with aliphatic chains terminated by tetra(ethylene glycol) (BTA) and a 20 kg/mol telechelic poly(ethylene glycol) decorated with the same hydrogen bonding BTA motif on both ends (BTA-PEG-BTA). The powerful combination of rheometric and cryo-TEM experiments with simulations provides detailed insights into the origin of the observed behavior, which is the competition between the dynamic interactions of the two compounds. The coarse-grained model used in simulations implies a universal validity of these findings for a variety of different chemical compounds. It is concluded that interactions between not only the single associating units, but also their changing organization in space with changing relative composition, play a crucial role in the emerging mechanics of binary and multicomponent gels, and therefore have implications in understanding and tailoring the viscoelastic properties of biological networks or designing mixed hydrogels with desired properties.