Norbornenyl-substituted thiophenes and terthiophenes: Novel doubly polymerizable monomers

The synthesis and polymerization of norbornenyl-substituted thiophenes (2 a nd 4) and terthiophenes (3 and 5) are reported. All monomers readily underg o ring-opening metathesis polymerization (ROMP) using the ruthenium catalys t, Cl-2(PPCy3)(2) Ru=CHPh (1). The terthienyl monomers 3 and 5 were directl y polymerized onto the surface of a gold electrode via electrochemical oxid ation of the capping terthienyl units, while the direct electrochemical hom opolymerization of 2 was not achievable, which is consistent with previous literature reports for similarly substituted thiophenes. Chemical polymeriz ation of the terthienyl segments of 3 and 5 using FeCl3 yielded insoluble m aterials. Finally, polymers obtained from the ROMP procedure were further c ross-linked using the oxidative techniques described above, yielding highly networked materials which displayed an increase in thermal stability and e lectrical conductivity relative to their single-chain polymeric precursors.