Isomerization of Diphenyl Polyenes. Part II. Fluorescence Properties of 1,8-Diphenyl-1,3>5,7-octatetraene in Poly (vinyl alcohol) Film

Abstract

The effect of temperature on the fluorescence properties of 1,8-diphenyl-1,3,5,7-octatetraene (DPO) in polyvinyl alcohol) film (PVA) was investigated in the range from 295 to 428 K. Upon heating above 353 K, the quantum yield of D PO increases rapidly. This effect is irreversible, similarly as the optical density in the long wavelength absorption band (320-440 nm). It has its origin in the cis-trans conversion of DPO molecules in PVA film at high temperatures. The behaviour of the fluorescence anisotropy in the same temperature range was also investigated. The emission anisotropy was found to be a viscosity indicator in the microenvironment of the DPO molecules in PVA film.

Isomerization of Diphenyl Polyenes. Part VI. Properties of l,8-Diphenyl-l,3,5,7-octatetraene Fluorescence in Poly (vinyl alcohol) and other Polymer Films

“…As already shown in [16], the fluorescence quantum yield, grows dramatically upon heating the DPO sample in PVA to above 358 K. Table 1 summarizes the quantum yield values determined for DPO in different polymers either non-heated or heated to 423 K. In the case of DPO in PVCh, PVF and EtA (nonheated samples), <P F amounts to about 0.22, being very low for the non-heated DPO sample in PVA (0.03) and even lower than for DPO in cyclohexane and methanol. The values of for DPO in PVCh, PVF and EtA heated to 423 K are almost the same as for the nonheated samples, while for the heated DPO in PVA a strong increase in <P F is observed, even to 0.32, which is markedly higher than the quantum yield in the remaining polymers.…”

“…The methods of measuring the absorption and fluorescence spectra, and the quantum yields and emission anisotropies were described in [15][16][17]. Fluorescence decays were measured on a K 2 multifrequency cross-correlation phase and modulation fluorometer at the Biochemistry Department of the University of Ancona, Italy.…”

“…Chattopadhyay et al [14] obtained <*> F = 0.085 and r = 6.7 ns, = 0.088 and x = 1.1 ns and <P F = 0.091 and x = 6.8 ns in cyclohexane, benzene and methanol, respectively. Recently, unusual behaviour of the DPO absorbance and quantum yield was observed in polyvinyl alcohol) (PVA) films at temperatures above 358 K [15,16]. At such temperatures the absorbance and quantum yield strongly increase.…”

Isomerization of Diphenyl Polyenes. Part VIII. Absorption and Fluorescence Properties of l-Phenyl-4-diphenylthiophosphinyl Butadiene in Poly (vinyl alcohol) Film

“…In the latter cases, i.e. for l,6-diphenyl-l,3,5-hexatriene (DPH) and 1,8-diphenyl-l,3,5,7-octatriene (DPO) in PVA, an unusual behaviour of absorbance and quantum yield was ob served above the glass transition temperature (Tg = 358 K), which enabled the conclusion that above this temperature thermal cis-trans isomerization occurs in the ground state [1,3,5,6]. In addition, based on quantum yield and mean fluorescence lifetime decay measurements it was found that for the three polyenes fluorescence emission is due to trans-trans and cistrans conformers.…”

“…In previous papers [1][2][3][4][5][6][7][8] the effect of temperature and light on the photophysical and photochemical properties of linear polyenes, Ph-(CH = CH)"-Ph, n = 2, 3, 4, in poly(vinyl alcohol) (PVA) films were investigated. The behaviour of the polyene with n = 2, i.e.…”