Synthesis and properties of polyacetylene and polynorbornene derivatives carrying 2,2,5,5-tetramethyl-1-pyrrolidinyloxy moieties

PROXYL-containing propargyl ester HCCCH2OCO-3-PROXYL (1), N-propargylamide HCCCH2NHCO-3-PROXYL (2), 1-pentyne-4,4-dimethyl ester HCCCH2C(CH3)(CH2OCO-3-PROXYL)(2) (3), and norbornene diester monomers NB-2,3-exo,exo-(CH2OCO-3-PROXYL)(2) (4), NB-2,3-endo,endo-(CH2OCO-3-PROXYL)(2) (5), and NB-2,2-(CH2OCO-3-PROXYL)(2) (6) (NB = norbornene, PROXYL = 2,2,5,5-tetramethyl-1-pyrrolidinyoxy) were polymerized to afford novel polymers containing the PROXYL radical at high densities. While 1 and 2 provided polymers with number-average molecular weights of 3300-29 800 in 60-65% yields in the presence of a Rh catalyst, monomers 4-6 gave polymers with number-average molecular weights up to 209 000-272 000 in 90-94% yields with a Ru catalyst. The formed polymers were thermally stable up to ca. 220 degrees C according to TGA and soluble in common organic solvents including toluene, CHCl3, and THF. Poly(1), poly(2), and poly(4)-poly(6) hardly exhibited absorption above 400 nm, which corresponds with their very light color. The oxidation/reduction gaps in the cyclic voltammograms of the present polymers were as small as 0.072-0.092 V, indicating large electrode reaction rates. All the PROXYL-containing polymers demonstrated the reversible charge/discharge processes, whose capacities were larger than 85 A h/kg. In particular, the maximum capacity of poly(1)- and poly(4)-based cells reached 117 and 107 A h/kg, which practically coincided with the theoretical capacity values (119 and 109 A h/kg, respectively).