Slide-ring elastomers have garnered a lot of interest for their potential use in dielectric elastomer actuators due to their intrinsically soft nature and high elasticity. However, the use of sliding cross-linkers has been constrained by their low miscibility with commonly used elastomer precursors and the specialized curing chemistries that are necessary for incorporating them into networks. Here, we have presented a method to produce vinyl functional polyrotaxane cross-linkers that are compatible with polysiloxanes and can be processed by industrially scalable methods. The sliding silicone films that were fabricated with these novel cross-linkers were highly extensible (>350%) and did not exhibit strain hardening even at high elongation. The composite films also retained the favorable dielectric properties of silicone elastomers such as the characteristic low dielectric loss. The modified polyrotaxanes present a robust platform for producing a new class of sliding silicone elastomers with well-defined networks structures.

While cyclic polymers have intrigued researchers for their novel set of architecture-driven rheological interactions, the possibility of incorporating them in topological systems has been limited by the availability of large ring polymers. Thus, the need for scalable methods to produce ring polymers has become apparent. Here, a facile method to prepare polysiloxane ring polymers by means of Piers-Rubinsztajn chemistry is presented. The one-pot nature and commercial availability of reagents additionally confirm the applicability of the method for large-scale production. Furthermore, a highly efficient yet simple purification method was developed for the isolation of pure ring polymers without linear side products.

Slide-ring elastomers have mobile cross-links that can slide on their axial polymers in a manner similar to a pulley on a zip line. This supramolecular network structure imparts unique mechanical properties to the elastomers, such as high deformability and low hysteresis upon cyclic loading, that are often favorable for dielectric elastomer actuators (DEAs). The utilization of this type of dynamic network for actuation has been limited by the low compatibility of slide-ring materials and common elastomer platforms used in DEAs. Here, a synthetic pathway is proposed to allow for incorporation of slide-ring cross-linkers into silicone networks.

No abstract

Slide-ring elastomers consist of mobile cross-links that can rearrange themselves within the network in contrast to conventional elastomers with fixed junctures. This unique feature affects the macroscopic mechanical properties of the sliding elastomers by imparting a distinct sliding elasticity that is caused by the distribution entropy of the sliding crosslinks. Slide-ring silicone elastomers exhibit two distinct time dependent elastic responses that can be credited to the conformational entropy of the polysiloxane chains and the distribution entropy of the threaded rings. In this work, the transition between rubber elasticity of the silicone chains and the sliding elasticity of the rings has been observed through linear viscoelastic studies. The extensional properties of the elastomers further corroborated the presence of two distinct time dependent viscoelastic profiles. This novel network structure presents the potential to design more intricate dielectric elastomer transducers with two distinctive modes of behavior determined by the operational speed of the system.