Photodegradation and Stabilization of PPO® Resin Blends

Pickett, James E.

doi:10.1007/978-94-011-3838-3_5

Cited by 10 publications

(11 citation statements)

References 32 publications

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“… In the presence of molecular oxygen, a superoxide radical is formed. A similar scheme was also proposed by Pickett for the photolysis of polyphenylene oxide. , Oxygen does not react with the excited benzoxazole or benzothiazole molecule effectively.…”

Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 72%

“…Photolysis of polymers in air and nitrogen often shows a variety of results, − with some polymers undergoing photooxidative reactions through the formation of charge transfer complexes with molecular oxygen …”

Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 99%

“…Investigation of Possible PBO Excimer Formation in Solution. Excimer formation has been shown to occur in many organic systems as well as in polymeric forms of poly(phenylene oxide), , PBO, and PBT . Such complexes exist only in the excited state, and their formation is often accompanied by the appearance of a new emission at longer wavelengths, the intensity of which increases with concentration…”

Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 99%

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Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

et al. 1996

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Several benzoxazole and benzothiazole compounds have been prepared and their extended configurations characterized by optical absorption and emission spectroscopy. In general, solutions of these compounds fluoresce strongly and exhibit emission spectral profiles which mirror their respective excitation spectra. One exception to this correlation results from a chromophore with a nonplanar ground state configuration which disrupts the extended π-network, promoting a strong hypsochromic shift of the absorption spectrum. The absorption, excitation, and emission spectra of these compounds also show a strong vibronic progression of ∼1300 cm-1 in accordance with the energy of ring-stretching modes for aromatic frameworks. This excited state molecular distortion is consistent with the ππ* nature of the optical excitation. Also, the energy gap between excitation and emission 0−0 bands of these benzoxazole and benzothiazole compounds and their polymeric forms are strongly influenced by the minimum allowed intermolecular space. In dilute solutions or for structures with bulky substituents, only small energy differences are observed between excitation and fluorescence 0−0 bands. In contrast, solid state samples devoid of side groups exhibit significantly larger energetic displacements accompanied by a pronounced broadening of both excitation and emission spectral profiles. These results suggest that strong intermolecular π-stacking interactions occur for the planar benzoxazoles and benzothiazoles in the solid state. Excited state lifetime decay measurements for PBO model compounds in toluene are monoexponential with essentially identical lifetimes under evacuated and standard pressure conditions. In the solid state, PBO and PBT model compounds exhibit biexponential luminescence decay lifetimes which were also not significantly affected by the presence of O2. Fibers of PBO and PBT revealed three oxygen independent, but wavelength dependent emitting species. The presence of only one emitting species for these benzoxazole compounds in solution, compared with their multiexponential lifetime behavior in the solid state, further supports strong π-interactions between these molecules in the solid state. This molecular configuration permits benzoxazole and benzothiazole compounds to undergo photoinduced electron transfer in the solid state, which in the presence of oxygen leads to the generation of superoxide.

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Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 72%

Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 99%

Section: Protonation Of Benzoxazole In Strong Acidsmentioning

confidence: 99%

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Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

et al. 1996

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“…These absorbers are photostable because their excited states can dissipate the absorbed energy as heat by a rapid internal hydrogen transfer [1,8]. An important aspect of the effectiveness of UVAs in the polymer is the amount of light which is absorbed at a certain depth in the polymer.…”

Section: Introductionmentioning

confidence: 99%

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

Diepens

Gijsman

2009

Polymer Degradation and Stability

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“…PET is a key step in biological systems, organic reactions, organometallic and inorganic chemistry, catalysis and molecular‐level electronics 8, 9. Poly(2,4‐dimethyl‐1,4‐phenylene oxide) (PPO),10, 11 poly(benzo[1,2‐ d :5,4‐ d ′]bisoxazole‐2,6‐diyl‐1,4‐phenylene) (PBO) and poly (benzo[1,2‐ d :4,5‐ d ′]bisthiazole‐2,6‐diyl‐1,4‐phenylene) (PBZT)12, 13 (Scheme ) have been reported to undergo self‐sensitized PET. In this mechanism, an excited polymer repeating unit undergoes electron transfer with another unit to generate a radical‐cation and radical‐anion pair.…”

Section: Introductionmentioning

confidence: 99%

Photodegradation mechanism and stabilization of polyphenylene oxide and rigid‐rod polymers

2005

Polymer International

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Poly(2,4‐dimethyl‐1,4‐phenylene oxide) (PPO), poly(benzo[1,2‐d:5,4‐d′]bisoxazole‐2,6‐diyl‐1,4‐phenylene) (PBO) and poly(benzo[1,2‐d:4,5‐d′]bisthiazole‐2,6‐diyl‐1,4‐phenylene) (PBZT), which are polymers with extended conjugated structures, undergo a self‐sensitized photo‐induced electron‐transfer reaction. A second component is not required. This article presents many similar observations on these polymers when they are exposed to light and evidence to support the proposed photo‐induced electron‐transfer mechanism. Methods to stabilize these polymers against photo‐oxidation are also described. Workers investigating other conjugated polymeric systems may find the experimental methods, observations and polymer stabilization approaches discussed in this review useful. Copyright © 2005 Society of Chemical Industry

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Photodegradation and Stabilization of PPO® Resin Blends

Cited by 10 publications

References 32 publications

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

Photodegradation mechanism and stabilization of polyphenylene oxide and rigid‐rod polymers

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