Absorption spectra polymers

The absorption spectrum of poly(2-methoxy-5-(2 -ethyI-hexyIoxy)-/mra-phenyIene vinylene) (MEH-PPV) is shown in Figure 7-8a. Phcnylene-based conducting polymers such as MEH-PPV exhibit multiple absorption features extending well into... 

Figure 15-24. Spectral response or devices nude wilh different PEOPT polymer thicknesses Al/C ) (35 nm)/PEOPT (30 nin)/PEDOT-PSS (110 unU/lTO (120 ninj/glass (solid circles) and AI/Cm (35 nm)/PEOPT (40 iini)/Pl DOT-PS.S (110 mn)/lTO (120 ninj/glass (open circles). The absorption spectrum of the PEOPT polymer is plollcd for comparison (solid line) (reproduced by permission of Wiley-VCH from Ref. (92]).

Figure 11-4. Electroluminescence and optical absorption spectrum of the soluble polymer MEH-PPV.

Maldotti (96) studied the kinetics of the formation of the pyrazine-bridged Fe(II) porphyrin shish-kebab polymer by means of flash kinetic experiments. Upon irradiation of a deaerated alkaline water/ethanol solution of Fe(III) protoporphyrin IX and pyrazine with a short intense flash of light, the 2 1 Fe(II) porphyrin (pyrazine)2 complex is formed, but it immediately polymerizes with second-order kinetics. This can be monitored in the UV-Vis absorption spectrum, with the disappearance of a band at 550 nm together with the emergence of a new band due to the polymer at 800 nm. The process is accelerated by the addition of LiCl, which augments hydrophobic interactions, and is diminished by the presence of a surfactant. A shish-kebab polymer is also formed upon photoreduction of Fe(III) porphyrins in presence of piperazine or 4,4 -bipyridine ligands (97). 

Figure 9 shows the electronic absorption spectrum of a PTTB film which has undergone extensive but incomplete reaction with bromine in a non-in-situ experiment. The absorption spectrum is that expected for a one-dimensional conjugated polymer. The sharpest absorption edge is at about 1490 nm (o.83 eV) and the absorption maximum is located at 1240 nm (1.0 eV). Thus, this material has a bandgap of about 0.83 eV. Note that two small... 

Photophysical Processes in Pol,y(ethy1eneterephthalate-co-4,4 -biphenyldicarboxyl ate) (PET-co-4,4 -BPDC). The absorption and luminescence properties of PET are summarized above. At room temperature the absorption spectrum of PET-co-4,4 -BPDC copolymers, with concentrations of 4,4 -BPDC ranging from 0.5 -5.0 mole percent, showed UV absorption spectra similar to that of PET in HFIP. The corrected fluorescence spectra of the copolymers in HFIP exhibited excitation maxima at 255 and 290 nm. The emission spectrum displayed emission from the terephthalate portion of the polymer, when excited by 255 nm radiation, and emission from the 4,4 -biphenyldicarboxylate portion of the polymer when excited with 290 nm radiation. 

Figure 26. Temperature dependence of absorption spectrum of CgAzoCioN+ Br complexed with anionic polymer, (a) polymer 4 and (b) polymer 1.

Jin et al. [487] synthesized and studied the PL and EL properties of polymers 403 and 404 that differ by the position of the alkoxy substituent in the phenyl ring, expecting different distortion of the polymer main chain (and consequently conjugation length) due to different steric factors for para- and ort/zo-substitution (Chart 2.98). The absorption spectrum of the ortho-polymer 403 showed a substantial blue shift of 40 nm compared to para 404 and a decrease in EL turn-on voltage (4.5 and 6.5 V, respectively). Both polymers demonstrated nearly the same PL and EL maxima (Table 2.1). 

In polymers the infrared absorption spectrum is generally very simple, considering the large number of atoms that are involved. This simplicity is due to the fact that many of the normal vibrations have almost the same frequency and so appear in the spectrum as one absorption band and, also from the strict selection rules that avoid many of the vibrations from causing absorptions. 

The ground states of the TIN and TINS stabilizers respond to the influence of the molecular environment in polymer films in almost the same manner as they do in solution. The absorption spectra of TIN in PMMA film (Figure 9) and TIN in PS film are similar to those observed for TIN in low polarity, non hydrogen-bonding solvents. A linear combination of the TIN planar) and TIN(non-planar) component spectra from the PCOMP analysis was used to fit the absorption spectrum of TIN in PMMA. 

The spectrum of TIN in PS is red-shifted compared to its spectrum in PMMA and so the relative proportion of each form could not be calculated using this method. However, the similarity between these two spectra suggests that a comparable proportion of TIN molecules in PS assume a non-planar conformation. The absorption spectrum of MeTIN in a PMMA film consists of a single absorption band (see Figure 9). This band is similar to that observed for MeTIN in solution suggesting that MeTIN exists almost entirely in a non-planar conformation in this polymer. 

An excitation-wavelength dependence at the longwave edge of the absorption spectrum has been observed not only for spectral displacement but also for other parameters such as lifetime, quantum yield and apparent rotational rate. Applications to the investigation of polymer rigidity and/or free volume, and to the study of biological systems and excited-state reactions have been developed. 

It was found from the absorption spectrum that 1.1 % of the incident photons were absorbed at 2537 A by a PMMA film of 0.5 ym thickness (Fig. 5). The molecular weight distribution and the average molecular weight of the coated polymer which was irradiated for the least irradiation time required for the dissolution of polymer coating in the developer were measured by gel-permeation chromatography (Fig. 7). 

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