Surpassing the Stiffness-Extensibility Trade-Off of Elastomers via Mastering the Hydrogen-Bonding Clusters

The current paradigm of elastomer design typically falls into the trade-off between stiffness and extensibility, which are the two key contributors to their overall mechanical performance. With a few reports on circumventing this trade-off behavior, e.g. increasing Young’s modulus without sacrificing extensibility, the design principles to achieve improvements in both stiffness and extensibility have rarely been demonstrated. Herein, with a model system, i.e., crosslinked polydimethylsiloxane (PDMS) network, we demonstrate two approaches that can surpass the stiffness-extensibility trade-off and provide significant improvement in both parameters. Such an achievement is realized by introducing rationally arranged hydrogen-bonding units, i.e., ureidopyrimidone (UPy), leading to simultaneously improved Young’s modulus and extensibility up to 158 and 3 times, respectively. Based on the experimental results, we also propose a microscopic picture of network rearrangement during the stretching process. Moreover, using this picture we further improved Young’s modulus of the elastic network without affecting its extensibility through mastering the distribution of UPy clusters. Small-angle X-ray scattering (SAXS) and neutron scattering (SANS) were also performed to reveal the relationship between the UPy distribution and the morphology/UPy cluster of the elastomers.