Light-absorbing polymer

Sehgal, A. and Seery, T.A.P., Anomalous dynamic light scattering from solutions of light absorbing polymers, Macromolecules, 32, 7807, 1999. 

Figure 14.9. Schematic of a solution-grown nanorod/nanotube array (e.g., ZnO), which can be coupled with a light absorbing polymer to produce a functional organic-inorganic photovoltaic device. 

An additional Step 1 light absorbing polymer agent, (11), was prepared by the author [1] in a subsequent investigation and used as an organic anti-reflective coating. 

Wood contains 15-30% lignin, an aromatic UV- and visible-light-absorbing polymer with a very complex structure (see Chart 8.1), and photochemical alterations of wood are essentially determined by reactions initiated by bond breakages in the... 

M. Heeney, C. Bailey, W. Duffy, M. Shkunov, D. Sparrowe, S. Tierney, W. Zhang and I. McCulloch, Light absorbing polymers incorporating 3,6-dialkylthieno[3,2-Z)]thiophene for photovoltaic applications. PMSE Prepr.,... 

Lee J, Leventis HC, Haque SA, Torres T, Gratzel M, Nazeeruddin MdK (2011) Panchromatic response composed of hybrid visible-light absorbing polymers and near-IR absorbing dyes for nanocrystalline Ti02-based solid-state solar cells. J Power Source 196 596-599... 

There is the possibiUty of a chemical reaction between a plastic and a colorant at processing temperatures. Thermal stabiUty of both the polymer and colorant plays an important role. Furthermore, the performance additives that may have been added to the resin such as antioxidants, stabilizers, flame retardants, ultraviolet light absorbers, and fillers must be considered. The suitabiUty of a colorant in a particular resin must be evaluated and tested in the final apphcation after all processing steps to ensure optimum performance. 

Ubichromenol synthesis, 3, 752 Ugi reaction, 5, 830 Uliginosin B, bromo-molecular dimensions, 3, 621 Ullman and Fetvadjian synthesis quinolines, 2, 477 Ullman synthesis acridines, 2, 470-benzacridines, 2, 470 Ultraviolet light absorbers in polymers, 1, 397-398 Ultraviolet spectroscopy heterocyclic compounds reviews, 1, 78... 

Ultraviolet light absorbers will be discussed in more detail under another section. Suffice it to say that their incorporation into a polymer can provide a useful antioxidant function. 

Additives used include plasticisers such as diphenyl diethyl ether, ultraviolet light absorbers such as 5-chloro-2-hydroxybenzophenone (1-2% on the polymer) and stabilisers such as phenoxy propylene oxide. 

The alternative approach is to add a photodegradant which is an ultraviolet light absorber. However, instead of dissipating the absorbed energy as heat (as with conventional ultraviolet absorbers) the aim is to generate highly reactive chemical intermediates which degrade the polymer. One such material is iron dithiocarbamate. 

Applications Chromatography is a preferred technique for additive analysis as it allows both separation of additives in a mixture and subsequent quantitation. Despite the developments in GC, this technique cannot separate many polymer additives. Even with its lower efficiency in comparison to GC, HPLC is today one of the cornerstones in a polymer additive laboratory. Judging by the number of publications in recent years, HPLC is first among analytical methods for additives (confirmation/identification/quantification). Most additives may be analysed by HPLC if they can be dissolved in an HPLC solvent and absorb UV light. Typical polymer/additive analyses are carried out using LPE followed by HPLC with UV or RI detection [605-611]. Verification of the identity of an analyte is then based on a combination of retention time, UV and RI evidence. RPLC is used most frequently for polymer/additive analysis, but normal-phase and SEC are also used. Consequently, techniques for additive analysis by HPLC are legion. 

Lawrence and Ducharme [16] have described a fast, simplified method for the detection of fluorescent whiteners in polymers, in which the polymer dissolution was applied directly to the thin layer. Similarly, using fluorescent indicator-containing layers, the presence of small amounts of UV light-absorbing antioxidants in polymers could be determined. 

The mechanisms of photochemical degradation of a polymer are rather difficult to study as the observed degradation is typically a result of the effect of light on the contaminants in the polymer rather than the pure polymer. Studies typically look for the degradation products, either low molecular weight volatiles or radicals, or work to identify the wavelength of light absorbed by the system via spectroscopic methods. 

Is the UV-stabilization only due to the screening effect (or more precisely light absorbing effect in a spectral region where the absorption spectra of polymer and UV-stabilizer overlap) of the UV-stabilizers and/or can it be enhanced by an energy transfer from the excited polymer to the stabilizer molecule ... 

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