SOLUBLE CONJUGATED POLYMERS WITH DEGENERATE GROUND-STATE DERIVATIVES OF POLY(1,6-HEPTADIYNE)

We report the results of initial measurements on two derivatives of poly(1,6-heptadiyne): a di-ketone (PHDK) and a di-ester (PHDE). Both polymers have the degenerate ground state of poly(1,6-heptadiyne); both are soluble in common organic solvents. Electron spin resonance (ESR) measurements on pristine samples place an upper limit of 10(-4) spins per monomer for both polymers. At low doping levels, we observe a single doping-induced absorption band at an energy of approximately half the pi-pi* gap, E(g)/2; the doping-induced spectral features were fully reversible. In situ ESR and absorption measurements during doping show that charge is stored predominantly in spinless charge carriers. Because of the inequivalent carbons on the conjugated backbone, the results are discussed in terms of the (A = B)n polymer. Both PHDK and PHDE are relatively stable in air; the strength of the pi-pi* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value.