Triplet excimer formation of some vinylaromatic polymers and their monomeric analogues

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5566177

Jhon, N I

The temperature-induced interchange between nonexcimeric and excimeric phosphorescence was investigated at temperatures from 20 K to 240 K for poly [N-((vinyloxy)-carbonyl) carbazole] (PFCZ); poly[N-((allyloxy)-carbonyl) carbazole] (PACZ); and poly(3,6-dibromo-N-vinylcarbazole) (3,6PVKBr[sub 2]). The monomeric model compounds such as triphenylamine (TPA); N,N-diphenylamino-phenylmethyl ester of 2-methylpropanoic acid (DAPM); N-ethylcarbazole (NEC); and 3, 6-dibromo-carbazole (3, 6Br[sub 2]Cz) in polystyrene (PS); and polymethylmethacrylate (PMMA) polymer matrices were studied. In most cases phosphorescence spectra at low temperatures were structured, but as the temperature was raised a broad phosphorescence band at about 470 nm appears. The band has no structure and is thought to be due to excimeric triplet; it grows with increasing temperature and the low temperature band gradually disappears. Rates of excimer formation and dissociation were determined as a function of temperature as well as the corresponding activation energies. Activation energies for the trapping of triplet excitons at excimer-forming sites in the matrices were between 1.1 and 2.6 kJ/mol for carbazolyl-containing polymers. For a triphenylamine-containing polymer, PDAPM, the activation energy is 5.1 kJ/mol. The activation energies associated with excimer formation were related to the nature of the chromophore itself rather than to any constraints imposed by the backbone structure of the polymer. The activation energies for dissociation of the triplet excimers were dependent on the concentration of the amine. For DAPM, the evidence suggests that excimers formed in dilute polymer matrices are in a strained configuration which relaxes slowly compared to the excimer lifetime. Triplet exciton migration is not the rate-limiting step in excimer formation. Rather, the rate of trapping is controlled primarily by the action of bond formation in the excimeric species.

• Research Organization: Nevada Univ., Reno, NV (United States)
• OSTI ID: 5566177
• Country of Publication: United States
• Language: English

Related Subjects

664000* -- Atomic & Molecular Physics-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALKYL RADICALS
AROMATICS
AZAARENES
AZOLES
CARBAZOLES
EXCITONS
HETEROCYCLIC COMPOUNDS
LUMINESCENCE
MONOMERS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORESCENCE
POLYMERS
QUASI PARTICLES
RADICALS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TRAPPING
VINYL RADICALS