Polydicyclopentadiene (PDCPD) is a thermoset polymer of growing importance in the production of durable parts in the automotive industry due to its low cost, high stiffness and high impact resistance. PDCPD is formed through ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD). The majority of PDCPD materials are densely crosslinked, which leads to enhanced mechanical properties. However, the crosslinking mechanism remains debatable in the literature. Metathesis of both olefins within the DCPD monomer and thermally initiated olefin addition reaction are both proposed as the principle mode of crosslinking. Recently, our group reported synthesis of PDCPD by frontal ring-opening metathesis polymerization (FROMP) that allows rapid materials fabrication with minimal external energy. We observed that FROMP of allylic-substituted DCPD using Grubbs’ catalysts afforded both partially crosslinked and linear polymers. However, under ROMP conditions, only linear structures were obtained at various temperatures since ROMP of much less strained cyclopentene ring is not favored. Characterized by DSC, NMR and Raman spectroscopy, we systematically studied a series of DCPD monomers and investigated different mechanisms of crosslinking in ROMP and FROMP. This study not only contributes to mechanistic understanding of PDCPD crosslinking, but also provides insights into rational development of functionalized PDCPD for broader applications.

Investigation of crosslinking mechanism in ring-opening metathesis polymerization of functionalized dicyclopentadienes

256th National Meeting (2018)

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