Frontal Polymerization of Hydroxylated Norbornene: Fabrication of Functional Foams for Catalytic Applications

Polymeric foams are versatile materials with direct applications in numerous fields, including insulation and heterogeneous catalysis. Existing polymeric foam production processes include several stages, many of which are energy intensive. Herein, we report the single-step fabrication of polymeric foams using the low energy technique, frontal ring opening metathesis polymerization (FROMP), and demonstrate their use as scaffolds for the deposition of palladium nanoparticles. Initially, we studied FROMP of 5-hydroxymethyl-2-norbornene (HMNB) monomer using the second-generation Grubbs catalyst (G2) as initiator. In contrast with the model FROMP system of dicyclopentadiene (DCPD), HMNB is a liquid that contains hydroxyl groups capable of inhibiting G2. By incorporating 10 wt% n-pentane within FROMP mixtures, we successfully fabricated hydroxyl-containing foams with high porosities. The presence of hydroxyl groups enhanced the material’s ability to bind and uniformly disperse palladium nanoparticles (Pd NPs) as compared to DCPD foams. Coupled with a more hydrophilic surface, the generated foams were demonstrated as efficient catalytic scaffolds for cross-coupling reactions with activities comparable to that of free NPs. Our results demonstrate that HMNB can be polymerized using FROMP in the presence of a blowing agent to make functional foams that serve as a platform for heterogeneous catalysts development. We envision that these novel foams have potential use as scaffolds in flow chemistry.