Accession Number : ADA260002


Title :   Luminescence and Picosecond Photo-Induced Absorption of Polyaniline


Descriptive Note : Technical rept. 31 MAy 1991-30 Jun 1992


Corporate Author : PENNSYLVANIA UNIV PHILADELPHIA DEPT OF CHEMISTRY


Personal Author(s) : Kim, K ; Lin, L B ; Ginder, J M ; Gustafson, T L ; Epstein, A J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a260002.pdf


Report Date : 29 Jun 1992


Pagination or Media Count : 8


Abstract : The photoluminescence and photoinduced absorption are reported for leucoemeraldine and emeraldine forms of polyaniline in the picosecond to nanosecond time domain. The importance of bond vibration, charge tunneling and ring rotations in varying relaxation processes is determined. The temperature dependence of the photoluminescence decay time of the leucoemeraldine base dissolved in N-methyl pyrrolidinone is reported. The decay time decreases as the temperature increases. From the Arrhenius plot, the activation energy is estimated to be approx. 0.1 eV. These data suggest that backbone vibrations dominate this photoluminescence decay mechanism. From the comparison of the result to that of the monomer, aniline, it is concluded that a polaron-exciton confined in the basic unit including a ring and adjacent nitrogen atoms is responsible for the photoluminescence. The picosecond photoinduced absorption of emeraldine base films optically pumped at 2.1 eV and probed at 1.5 eV and 2.9 eV are compared with the previously measured picosecond photoinduced bleaching probed at 2.0 eV. While all three of them show initial fast decay, the photoinduced absorption at 1.5 eV does not show a substantial residue on the nanosecond time scale. This is in contrast to the photoinduced bleaching at 2.0 eV and 2.9 eV photoinduced absorption for which more than half of the signal remains even after a few nanoseconds. Preliminary measurements of emeraldine base films at a probe energy of 2.9 eV indicate that the decay slows down when the temperature is lowered. For emeraldine base in N-methyl pyrrolidinone solution, this long lived tail in picosecond photoinduced absorption disappears. These data strongly suggest the importance of the ring-torsion.


Descriptors :   *ABSORPTION , *LUMINESCENCE , *ANILINES , ELECTRONICS , MEASUREMENT , OPTICS , PROBES , TEMPERATURE , VIBRATION , CONTRAST , ACTIVATION , METHYL RADICALS , PHOTOLUMINESCENCE , COMPARISON , ENERGY , FILMS , ATOMS , CHARGED PARTICLES , NITROGEN , TIME , PYRROLIDINES , ARRHENIUS EQUATION , ACTIVATION ENERGY , RESIDUES , DECAY , TIME DOMAIN , ROTATION , TUNNELING , RINGS , CHEMICAL BONDS , AMINES , SCALE , SIGNALS , MONOMERS , RELAXATION


Subject Categories : Radiation and Nuclear Chemistry
      Polymer Chemistry
      Optics
      Thermodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE