Ultraviolet Stabilization of Polyamides

Werner, Thomas; Woessner, Gottfried; Kramer, Horst E. A.

doi:10.1021/bk-1981-0151.ch001

Cited by 20 publications

(3 citation statements)

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“…[11,12] The apparent simplicity of the process is misleading, as in the excited state there are numerous processes (radiative and nonradiative) that may compete with the proton transfer, such as radiative emission (fluorescence) and internal rotations, which may lead to conical intersections or intersystem crossings. Conical intersections (CI) with the ground electronic state are suspected to be the most efficient way to deactivate the excited state without emission of radiation.…”

Section: Introductionmentioning

confidence: 99%

Modulating the Photochemistry of Bipyridylic Compounds by Symmetric Substitutions

et al. 2010

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A quantum electronic study of the effect of substituents on (2,2'-bipyridyl)-3,3'-diol and (2,2'-bipyridyl)-3,3'-diamine is presented. A large difference in the photochemical behavior between the original and the substituted selected systems is expected. For the sake of simplicity, the study is restricted to the symmetrically bi-substituted compounds: fluorine, the more electronegative atom and thus a strong σ-acceptor but also a weak π-donor group, and NO(2), a strong π-acceptor substituent. Among the large set of compounds studied, two receive special attention: 5,5'-dinitro-(2,2'-bipyridyl)-3,3'-diamine and 6,6'-difluoro-(2,2'-bipyridyl)-3,3'-diol. While in the former case the nitro substitution transforms (2,2'-bipyridyl)-3,3'-diamine, previously suggested to behave as a photomemory material, into a simple fluorescent species, the latter substitution turns (2,2'-bipyridyl)-3,3'-diol into a fresh new candidate for a photomemory device.

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Section: Introductionmentioning

confidence: 99%

Modulating the Photochemistry of Bipyridylic Compounds by Symmetric Substitutions

et al. 2010

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“…Intramolecularly hydrogen-bridged UV absorbers, such as 2-(2-hydroxyaryl)benzotriazoles (HBzTs) or 2-(2-hydroxyphenyl)-4,6-diaryl-1,3,5-triazines (HPTs), are widely used in polymer materials. − All of these compounds have one characteristic in common: an excited state intramolecular proton transfer (ESIPT) in the excited singlet state S 1 opens a pathway for the transformation of harmful ultraviolet radiation into thermal energy. In the case of HPTs, this was first investigated for the 2-hydroxyphenyl-1,3,5-triazines (see Scheme ) in the pioneering work of Shizuka et al 10a-f Fundamental contributions to charge transfer in the excited state in general and the subsequent deactivation of excited hydrogen-bonded complexes have been made by Mataga and his group. − It has also been well established that the chemical characteristic of an additive itself is not alone the decisive factor for assessing the effectiveness of light protection.…”

Section: Introductionmentioning

confidence: 99%

Influence of Polymer Matrixes on the Photophysical Properties of UV Absorbers

et al. 2001

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The copolymerization parameters for monomer pairs of the copolymerizable UV absorbers MA-TIN 1 (2-[2-hydroxy-3-tert-butyl-5-(O-[2-hydroxy-3-(2-methylpropenoyloxy)-propyl]-2-carbonyloxyethyl)phenyl]benzotriazole) and MA-TZ 1 (2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(2-hydroxy-3-[2-methylpropenoyloxy])propoxyphenyl]-1,3,5-triazine) with styrene and methyl methacrylate were determined. The UV absorbers were present to a higher extent in the copolymers than they are when simply present as mixtures of monomeric UV absorbers in the monomer feed. At higher temperatures, the radiationless deactivation from the excited proton-transferred singlet state becomes more efficient for the UV absorbers physically admixed to the polymer than for the respective polymeric UV absorbers. MA-TZ 1 embedded in poly(methyl methacrylate) shows an equal increase of phosphorescence intensity with UV irradiation time as the decrease of the proton-transferred fluorescence. By combining fluorescence and phosphorescence measurements it becomes possible to estimate the proportion of UV stabilizer molecules with an intermolecular hydrogen-bridge to poly(methyl methacrylate) and which are not suitable for light protection of polymers at room temperature. At low pressure and temperature, the increase of light-induced phosphorescence was delayed. This “phosphorescence induction” phenomenon can be put down to the free volume of polymer matrixes, in which various UV absorbers have been incorporated. The emission spectroscopic results are applicable to products which are customary in trade, as shown by investigations on a clear coat binder system.

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“…This growth has been fueled by a wide range of potential applications, including lasers, 1,2 energy/data storage devices and optical switching, 3,4 Raman filters and hard-scintillation counters, 5 polymer photostabilizers, 6 and triplet quenchers. 7 Other uses center about electroluminescent materials with photochemical stability, resistance to thermal degradation, and low self-absorption and LED materials.…”

Section: Introductionmentioning

confidence: 99%

Comparison of methods for calculating the properties of intramolecular hydrogen bonds. Excited state proton transfer

Kar

Scheiner

C̆uma

1999

The Journal of Chemical Physics

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A series of molecules related to malonaldehyde, containing an intramolecular H-bond, are used as the testbed for a variety of levels of ab initio calculation. Of particular interest are the excitation energies of the first set of valence excited states, n* and *, both singlet and triplet, as well as the energetics of proton transfer in each state. Taking coupled cluster results as a point of reference, configuration interaction-singles-second-order Møller-Plesset ͑CIS-MP2͒ excitation energies are too large, as are CIS to a lesser extent, although these approaches successfully reproduce the order of the various states. The same may be said of complete active space self-consistent-field ͑CASSCF͒, which is surprisingly sensitive to the particular choice of orbitals included in the active space. Complete active space-second-order perturbation theory ͑CASPT2͒ excitation energies are rather close to coupled cluster singles and doubles ͑CCSD͒, as are density functional theory ͑DFT͒ values. CASSCF proton transfer barriers are large overestimates; the same is true of CIS to a lesser extent. MP2, CASPT2, and DFT barriers are closer to coupled cluster results, although yielding slight underestimates.

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Ultraviolet Stabilization of Polyamides

Cited by 20 publications

References 0 publications

Modulating the Photochemistry of Bipyridylic Compounds by Symmetric Substitutions

Modulating the Photochemistry of Bipyridylic Compounds by Symmetric Substitutions

Influence of Polymer Matrixes on the Photophysical Properties of UV Absorbers

Comparison of methods for calculating the properties of intramolecular hydrogen bonds. Excited state proton transfer

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