Forgotten monomers: free radical polymerization behavior of norbornadiene derivatives in comparison with methyl methacrylate

The free radical polymerization behavior of three norbornadiene derivatives was studied as a function of their structure. The compounds examined were 3-ethoxycarbonyl-tricyclo[3.2.1.02,4]oct-6-ene 1 (liquid), 2-carbethoxybicyclo[2.2.1]-2,5-heptadiene 2 (liquid) and 2-carboxybicyclo[2.2.1]-2,5-heptadiene 3 (solid). They were polymerized in bulk and in benzene solutions. The tricyclic compound 1 was the least reactive monomer whereas the bicyclic derivatives 2 and 3 readily polymerized radically to high conversions. The corresponding polymers were isolated and their structure were determined by means of IR- and NMR spectroscopy. The polymerization of 3-ethoxycarbonyl-tricyclo[3.2.1.02,4]oct-6-ene 1 is supposed to proceed through a simultaneous ring opening–ring closing mechanism. The corresponding polymer poly-1 shows low molecular weights. The polymerization results were compared with those obtained for a conventional solution polymerization of methyl methacrylate.