Homogeneous polymer network is highly attractive due to its synthetic ease, high purity and straightforward mechanical property. We are interested in Diels-Alder (DA) chemistry for macromolecular syntheses due to its simplicity, scalability, and absence of catalysts. However, most of the common DA reactants are consisted of two components, an electron-rich diene and an electron-poor dienophile. As a result, there are associated challenges such as stoichiometry, solubility, and long synthetic steps. We propose that a highly reactive single component will resolve these issues. Cyclopentadiene (CPD) is the most promising candidate due to its unique property of serving as both diene and dienophile to form dicyclopentadiene (DCPD). Furthermore, its dimer's known retro-DA at 180 °C is ideal for selective depolymerization. Intriguingly, not many efforts have been put into exploring this potential compound, partly due to the historically significant challenge of handling its reactivity, dating back to Staudinger and Stille. Wudl later controlled the instability of the CPD monomer by synthesizing a protected cyclic DCPD monomer, which was then cracked in situ at high heat. A single-component polymer network was synthesized with trimer formation as the crosslinking point. However, the specific cyclic design of the monomer and trimer crosslinking have limited the syntheses of new DCPD functional materials significantly. We are inspired that with our strategy to gain access to a variety of pure CPD derivatives, new DCPD materials can be obtained. Specifically, we utilized our previously reported norbornadiene-tetrazine cascade reactions to synthesize and isolate a pure 4-arm CPD monomer. A new highly crosslinked DCPD polymer network was successfully synthesized. The material is tough and has fast shape-recovery with Tg of 22 °C. The storage modulus is 1.4 GPa before Tg and 5.0 MPa after Tg. The material is ideal for shape-memory effect and is selectively depolymerized at 150 °C with proper additives.

Cyclopentadiene derivative as a single component, catalyst free to form a flexible polymer network

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.