Degenerate ground-state conjugated polymers exhibit large third-order nonlinear optical susceptibilities, including substantial two-photon absorption. With the use of a machine architecture suited to these material properties, ultrafast optical processors are possible. A four-wave mixing optical correlator was built with an air-stable, processable, degenerate ground-state conjugated polymer, poly(1,6-heptadiester). The continuously updatable processor correlates two 5000-pixel images in less than 160 femtoseconds, achieving peak processing rates of 3 x 10(16) operations per second.
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 π−π* gap, Eg/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 π−π* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value.
AD-A281 176 'The ESR of electrooxidation products of orthogonally bridged dimers of ,a-Coupled thiophene oligomera and spiro-fused phenylene-thiophene mixed oligomers was studied as a function of temperature. ESR measurements on the one-electron oxidation products indicate that the charge remains on a single oligomer unit and does not hop between the two bridged oligomer chains for temperatures up to 300 K. This is evident from the presence of hyperfine structure in ESR spectra for the dimers of short-chain oligomers and the small temperature-dependent line broadening for longer chain spiro dimers, characteristic of a low-energy process such as the paramagnetic site moving along the oligomer chain length. The activation energy for a paramagnetic center moving along the oligomer chain length has been estimated at <100 cm 1 . The incorporation of phenylene into the oligomer unit shifts oxidation potentials anodic and also inhibits the mobility of the polaron along the Ahconjugated oligomer segment. Evidence for formation of u-u dimers in solutions of 7-mT has also been obtained. The ESR of electro-oxidatlon products of orthogonally bridged dimers of aa-coupled thiophene oligomers and spiro-fused phenylene-thiophene mixed oligomers was studied as a function of temperature. ESR measurements on the one electron oxidation products indicate that the charge remains on a single oligomer unit and does not hop between the two bridged oligomer chains for temperatures up to 300K. This is evident from the presence of hyperfine structure in ESR spectra for the dimers of short chain oligomers and the small temperature dependent line broadening for longer chain spiro dimers, characteristic of a low energy process such as the paramagnetic site moving along the oligomer chain length. The activation energy tor a paramagnetic center moving along the oligomer chain length has been estimated at <100 cm-I. The incorporation of phenylene into the oligomer unit shifts oxidation potentials anodic and also inhibits the mobility of the polaron along the x-conjugated oligomer segment. Evidence for formation of x-x dimers in solutions of 7-mT has also been obtained.
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