The photophysical behavior of poly (p-phenylphenylenevinylene) (PPPV) and several oligomeric model compounds in isotropic and anisotropic samples is investigated by means of polarized fluorescence spectroscopy. As long as excitation energy transfer and mutual alignment are considered, the behavior of PPPV can be modeled by a chain consisting of a distribution of independent oligomeric segments. The results of fluorescence polarization, e.g., the nonzero value of r in isotropic PPPV, cast doubt on the application of the semiconductor band model but favor an interpretation of spectroscopic properties in terms of molecular transitions. The orientation coefficients of the oligomers and of PPP V in stretched polyethylene are determined.The change of fluorescence spectra of oriented PPPV in stretched polyethylene demonstrates directly that conformational changes of the macromolecule influence the pathway of energy transfer.

The orientational order parameters of a dendritic liquid crystal organo-siloxane tetrapode oligomer, determined using polarized infrared spectroscopy

An extensive investigation of the photostability and the thermo-oxidative stability is presented for 2,2@,7,7@tetrakis(biphenyl-4-yl)-9,9@-spirobiÑuorene and 2,2@,4,4@,7,7@-hexakis(biphenyl-4-yl)-9,9@-spirobiÑuorene. Both compounds are conjugated fully aromatic systems that are being discussed as active functional materials for a variety of advanced applications. The e †ect of atmosphere, sample thickness and preparation procedure on photo-oxidative degradation are investigated in detail by absorption and Ñuorescence spectroscopy. Distinct mechanisms are described in terms of relevant parameters such as the quantum yields of the photo-oxidation and the Ñuorescence. No oxidative degradation could be detected under nitrogen. In ambient air a strong decrease of the Ñuorescence performance is found due to e †ective quenching by defective chromophores. Chemiluminescence investigations were performed to characterise the thermo-oxidative behaviour in the temperature region between 300 and 450 K. It becomes clear that even a stable chemical structure such as the investigated aromatic system does not guarantee sufficient photostability with regard to light emitting properties.

Polarized fluorescence spectroscopy is used to investigate the photophysical behavior of poly(p‐phenylphenylenevinylene) (PPPV) in polystyrene matrix in comparison with oligomeric model compounds. For this purpose PPPV is modeled by a chain consisting of a distribution of independent oligomeric segments. Excitation energy transfer (EET) between the segments depends on the wavelength of excitation, not only for transfer along an isolated polymer chain, but also for intermolecular transfer at high concentration of PPPV. The spatial range of EET, as indicated by fluorescence depolarization, is reduced for excitation at the long wavelength edge of the absorption spectrum (“red‐edge‐effect”). © 1995 John Wiley & Sons, Inc.

Stationary polarized fluorescence spectra of poly( 1 ,Cphenylene-1 -phenylvinylene), poly( 1,4-phenylene-l,2-diphenylvinylene) and poly[ 1,4-phenylene-l,2-bis(4-phenoxyphenyl)vinylene] in tetrahydrofuran solution and in polystyrene films were recorded at room temperature. In these matrices, different behaviour is found concerning the Stokes shift, the degree of polarization and the quantum yield; it is interpreted as a viscosity induced effect. The commonly accepted model of a conjugated polymer chain to consist of independent segments of various length should not be applied to the poly(pheny1ene-arylviny1ene)s studied in this work.