Poly transition energies

Fig. 10. Lowest transition energies for ladder and linear polysilanes. Values for linear poly silanes are cited from reference 44.

The sharpness of the UV absorption and emission bands corresponding to HOMO<-> LUMO transition is also a measure of delocalization. The transition energy depends on the location of a polymer skeleton where a photon is absorbed or emitted, if electron orbitals are localized on parts of the skeleton. A sharp UV band of poly(n-decyl-(S)-2-methylbutylsi-lane) indicates the delocalization of HOMO and LUMO. Table 2 summarizes the location... 

Table 5. Core level binding energies, and transition energies and intensities for low energy shake up structures in poly para-substituted styrenes...

Transition Energies and Spectrum. The UV spectrum of poly(vlnyl p-azldobenzoate) Is the same as that of ethyl p-azldobenzoate. The spectrum of the latter in n-hexane solutions is shown in Fig.4 with the calculated transition energies and oslllator strengths. 

Most of the data refers to poly(GC) poly(GQ and its 5-methyl cytosine derivative, poly(Gm C)-poly(Gm C). The ionic strength dependence of the B-Z transition energy presented is based on the relation [85F1] (see Fig. 2) ... 

The PL spectrum and onset of the absorption spectrum of poly(2,5-dioctyloxy-para-phenylene vinylene) (DOO-PPV) are shown in Figure 7-8b. The PL spectrum exhibits several phonon replica at 1.8, 1.98, and 2.15 eV. The PL spectrum is not corrected for the system spectral response or self-absorption. These corrections would affect the relative intensities of the peaks, but not their positions. The highest energy peak is taken as the zero-phonon (0-0) transition and the two lower peaks correspond to one- and two-phonon transitions (1-0 and 2-0, respectively). The 2-0 transition is significantly broader than the 0-0 transition. This could be explained by the existence of several unresolved phonon modes which couple to electronic transitions. In this section we concentrate on films and dilute solutions of DOO-PPV, though similar measurements have been carried out on MEH-PPV [23]. Fresh DOO-PPV thin films were cast from chloroform solutions of 5% molar concentration onto quartz substrates the films were kept under constant vacuum. 

Fluorescence and phosphorescence spectra of poly(propynoic acid)(FPA), polyphenylene (PP), and DPAcN show that the difference of energies between the lower excited singlet and triplet states, as observed in the case of PP (583 nm) and DPAcN (528 nm), is considerably greater than that of poly(propynoic acid) (270—300 nm) which besides transitions may undergo rr - transitions. PCSs showing only... 

Fluorinated poly(arylene edier)s are of special interest because of their low surface energy, remarkably low water absorption, and low dielectric constants. The bulk—CF3 group also serves to increase the free volume of the polymer, thereby improving various properties of polymers, including gas permeabilities and electrical insulating properties. The 6F group in the polymer backbone enhances polymer solubility (commonly referred to as the fluorine effect ) without forfeiture of die thermal stability. It also increases die glass transition temperature with concomitant decrease of crystallinity. 

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