Dynamic Remodeling of Covalent Networks via Ring-Opening Metathesis Polymerization

Abstract

Reversible transformations in bulk polymers offer numerous possibilities for materials remodeling and reprocessing. While reversible systems based on dynamic covalent chemistry such as the Diels–Alder reaction and transesterification have been intensively studied to enable local bond dissociation and formation, reports regarding the reversion from bulk network polymers to monomers are rare. Herein, we report a reversibly polymerizable system based on ring-opening metathesis polymerization of cyclopentene derivatives in the bulk state. The network polymer is thermodynamically stable and mechanically robust at room temperature and readily depolymerizes at elevated temperatures to yield liquid monomers that are repolymerized to cross-linked polymers by simply cooling to room temperature. This reversible process was characterized by differential scanning calorimetry and rheological tests.

Highly active ruthenium metathesis catalysts enabling ring-opening metathesis polymerization of cyclopentadiene at low temperatures

“…Ru-8 was then applied to the ROMP of functionalized cyclopentenes, which have even lower strain energies than cyclopentene, some of which have never been used in ROMP (Supplementary Tables 10–17). Recently, the Moore group reported the reversible polymerization of 4-substituted cyclopentenes for the interconversion of a polymer and a neat monomer through control of the reaction temperature 50 . Although the ROMPs of 4-substituted cyclopentenes have been reported with G-II and G-III , 3-substituted cyclopentenes, which have even lower ring strains than the 4-substituted derivatives, are still challenging with the previously reported catalysts 9,17,20 .…”

Toward Stimuli‐Responsive Dynamic Thermosets through Continuous Development and Improvements in Covalent Adaptable Networks (CANs)

“…Exploiting the dynamic properties of polypentenamers, Moore and co‐workers reported a reversibly polymerizable system based on ring‐opening metathesis polymerization (ROMP) of di‐, and tricyclopentene derivatives 22. Deliberate structural modifications within the periphery of the cyclopentene monomers enabled a decrease in the ring strains, and by that, a significantly lower ceiling temperature for depolymerization was achieved.…”

Cross-linker control of vitrimer flow

“…11,12 A more recently reported class of CANs that exchange by associative mechanisms, or vitrimers, [13][14][15][16] maintain their cross-linked structure during swelling and heating, but can still be remolded and repaired. 5 A wide array of associative dynamic covalent chemistries have been employed in vitrimers, including transesterification, [17][18][19] olefin metathesis, 20,21 dioxaborolane exchange, [22][23][24] silyl ether exchange, 25 and several others. [26][27][28][29][30][31][32][33][34][35] Surprisingly, despite the number of reactions studied, there are no systematic studies that examine the effect of the cross-linker structure on vitrimer properties.…”