Transient polymer networks with a temporal hierarchy of energy dissipation have advantages in many applications, ranging from injectable hydrogels to self-healing materials. However, their structure and rheology are often estimated based on their permanent network equivalents. To account for this, we extend the mean-field Miller–Macosko’s recursive model to predict the network percolation in metallo-supramolecular polymer networks. Moreover, a simple thermodynamic model is developed to predict the composition of metal complexes with different coordination geometries in a multi-component network. To challenge the theoretical framework with experiments, we form model network hydrogels upon the coordination of phenanthroline-functionalized tetra-arm poly(ethylene glycol) (tetraEPh) with a mixture of Co2+ and Fe2+ metal ions, which are proved to expose different coordination geometry preferences. We demonstrate that even small deviations in the stoichiometric ratio of ligand to metal ions or variation of the coordination geometry preference significantly changes the network structure, which results in remarkably different macroscopic properties compared to those of the equivalent permanent networks. The theoretical model can explain the variation of the lifetime and relative contributions of the fast and slow relaxation modes in the shear modulus at various metal ion compositions. Moreover, the model explains that the significant drop in the modulus in the presence of excessive metal ions is due to the profound formation of threefold connected polymer precursors. The developed theory forms a reliable framework for predicting the time evolution of the junction composition, network percolation, and defect formation in transient polymer networks.

In a model 4-arm pEG supramolecular network, connectivity defects are systematically introduced with different ratios of 8-arm pEG, resulting in intra-molecular loops, and providing a softer polymer network and higher self-diffusion coefficients.

Hydrogels are polymer networks swollen in water that are characterized by soft mechanics and high permeability. This makes them good candidates for separation and membrane technologies. The diffusion is controlled by the mesh size of the network, and this can be made tunable through the introduction of thermoresponsive polymers. However, this is still a developing field. To contribute to this development, a dual dynamic network is formed composed of four‐arm polyethylene glycol precursors in which each arm is functionalized with both a terpyridine moiety capable of forming reversible metal–ligand complexes along with branches of poly(N‐isopropylacrylamide) (pNIPAAm), which can be switched between expanded and collapsed states and therewith offers a path for switching the microscopic gel‐network mesh size, along with the macroscopic gel elasticity. The dually sensitive hydrogel has the capability of doubling its elastic modulus when going above the lower critical solution temperature (LCST) of pNIPAAm. In addition, the diffusive permeability of the hydrogel is switched upon change of temperature, whereby diffusants are trapped above the LCST of pNIPAAm. Moreover, it is possible to disassemble and reform the gel upon change of pH. With that, the hydrogel has potential application as a switchable and reversible membrane.

We discuss the connection between high-temperature mechanics, block structure, and composition of a model series of industrially relevant, soft, thermoplastic elastomers (TPEs) containing polydisperse hard blocks (HBs). The high-strain deformation behavior of these materials results from the combination of multiple dynamics in the system, i.e., the HB associations and the mobile and entangled amorphous phase. Many soft-TPEs show a reduction in toughness with increasing temperature. Molecular weight (Mw) has been shown to improve the temperature-dependent mechanics by increasing network connectivity. In this work, we investigate the possibility to increase the network connectivity by tuning block length at constant Mw and composition. The average number of HBs per chain can be used to quantify network connectivity; however, by using block statistics, we show how increasing this value is not enough to increase the high-temperature mechanics, especially in the case of polydisperse HBs. Since temperature affects the HB ability to associate with each other, only the number of associated HBs per chain determines network connectivity. The experimental results are consistent with modeling predictions, revealing how decreasing the average block length influences the crystal stability, which ultimately controls network connectivity, and how this relationship is affected by temperature.

Mussel-inspired side-chain functionalized supramolecular hydrogels based on nitrocatechol–Fe3+ physical complexations reveal three relaxation modes whose lifetime varies six orders of magnitudes from 0.1 s to 9.8 × 104 s.