Metal-free ring-opening metathesis polymerization (ROMP) utilizes organic photoredox mediators as alternatives, to traditional Metal-based ROMP initiators to allow the preparation Of polymers without residual metal contamination. Herein we report studies exploring the use: of endo-dicyclopentadiene (DCPD), a common ROMP monomer, to form linear polyDCPD and copolymers with norbornene. Subsequent cross-linking of the linear polyDCPD using thiol-ene chemistry allows for a completely metal-free preparation of cross-linked,polyDCPD. Furthermore, the examination of a: number of structurally related monomers offers insights into mechanistic details of this polymerization and demonstrates new monomers that can be utilized for metal-free ROMP.