Investigating the Stress–Strain Behavior in Ring-Opening Metathesis Polymerization-Based Brush Elastomers

Abstract

Brush networks are intriguing materials that are able to replicate the stress–strain behavior of soft tissue, but the effect of the backbone chemical composition on the network mechanics is largely unknown. Here, we show that brush elastomers made by ring-opening metathesis polymerization (ROMP) of norbornene-terminated poly­(dimethylsiloxane) macromonomers are less extensible than brush elastomers with the methacrylate backbone yet not as extensible (λmax) as predicted by the strain-stiffening parameter (β) derived from fitting the experimental stress–strain curves. The softness (E 0) and firmness (β) of the norbornene-based networks decrease with decreasing cross-link density as expected, but the λmax significantly drops when the grafting density becomes low enough, which has not been previously observed in this class of materials.

From macromonomers to bottlebrush copolymers with sequence control: synthesis, properties, and applications

“…Due to their disentangled nature, BBPs exhibit Rouse-like behaviors without a rubbery plateau when the sidechain MW does not exceed the critical MW for entanglement. 6,8,9,14,138,177,180,[192][193][194][195][196] This unique rheological property can lead to interesting mechanical properties such as supersoft and superelastic melts and networks. 132,138,144,[174][175][176][177] In melts and solutions, it has been demonstrated that various self-assembly behaviors can be tuned according to architectural types of BBP.…”

“…While the aforementioned BBPs for soft elastomers and plastomers can be synthesized via a living radical polymerization of MMs, it is worth noting that BBPs prepared from ROMP also exhibit the same mechanical properties. 8,9,[192][193][194][195][196] BBPs can be then cross-linked via in situ ROMP with dinorbornyl cross-linkers 192,193 or disulfide bond formation 9 or by adding photo-or thermal-cross-linking additives, 8,[194][195][196] to form supersoft elastomers. It has been demonstrated that BBPs can be used as self-healing materials, 8 pressure sensors, 195 3D printing materials, 194,293 and pressure-sensitive adhesives.…”

Synthesis of well-defined linear–bottlebrush–linear triblock copolymer towards architecturally-tunable soft materials

“…Consequently, networks formed of such LBBL triblocks with the same targeted chemical and architectural composition have a noticeable batch-to-batch difference in mechanical properties 23 . Additionally, PDMS-based bottlebrushes synthesized with this "grafting through" approach posses a backbone chemistry that is different from the PDMS side chains which affects the network mechanical properties 27 . Therefore, developing a protocol that minimizes impurities while also precisely con-trolling the molecular chemistry and architecture would ensure a high consistency in mechanical properties of a topologically driven soft material.…”

Dynamic Mechanical Properties of Self-Assembled Bottlebrush Polymer Networks

“…Depending on the network topology, BPNs can be either randomly or end cross-linked. In a random network, precursor bottlebrush polymers are cross-linked among functional groups on the bottlebrush backbone ,, or side chains , through permanent , or dynamic covalent bonds. , This cross-linking process, however, randomly divides a bottlebrush into sections with a wide distribution in MW. Under large deformations, the stress is localized and amplified along relatively short bottlebrush sections to result in network fracture.…”