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Polycarbonates photo-rearrangement

The chemical processes involved in polycarbonate photodegradation are not well defined. Much early work concentrated on the photo-Fries reaction, which involves rearrangement to... [Pg.329]

Miscellaneous.—Recent papers have reported the photodegradation of urethanes,247 the photolysis of organopoly(silanes),248 and the photodegradation of bisphenol-A-polycarbonate.249 The degradation in the last study was shown to involve chain scission, cross-linking, and the photo-Fries rearrangement. [Pg.533]

In addition to the above, photo-Fries rearrangements occur in various aromatic polyester films upon ultraviolet light irradiation [560, 561]. Also, photo-Fries rearrangements are believed to occur in polycarbonate resins as well [562]. This can be illustrated as follows ... [Pg.673]

Photolytic decomposition of polycarbonate films was shown to produce products that are also consistent with the photo-Fries reaction. These are salicylic acid and bisphenol type species [580]. This is in agreement with earlier studies that showed that a variety of processes, including rearrangements (photo-Fries) and photo-oxidation, can occur when bisphenol A-based polycarbonate is photolyzed [581, 582]. [Pg.674]

In yet other polymers, such as with bisphenol polycarbonates both photodegradation and photo-initiated oxidative reactions take place simultaneously. The direct photoreaction is a Erie s rearrangement reaction, while the oxidative reactions result in chain scission and discoloration of the polymer. The chemical pathways involved in the latter process are not well understood. [Pg.861]

Polycarbonates -0-C=0 group in the main chain. Photo-Fries rearrangement. [108, 109]... [Pg.862]

This reaction is important in polymer photochemistry, because it can occur with significant efficiency even in glassy, solid polymers. It is believed to contribute significantly to photo-induced yellowing in aromatic polymers, particularly polycarbonates (Kobsa, 1964 Li and Guillet, 1977). The photo-Fries rearrangement has also been identified as a source of photo-yellowing in aromatic polyamides (Wiles and Carlsson, 1980). [Pg.1046]

Scheme 15.3. Photo-Fries rearrangement in bisphenol-A polycarbonate. Scheme 15.3. Photo-Fries rearrangement in bisphenol-A polycarbonate.
Fig. 15.14. Quantum yield for chain scission (-o-), efficiency of photo-Fries rearrangement (- -), and absorption spectrum (—A-) of bisphenol-A polycarbonate [34],... Fig. 15.14. Quantum yield for chain scission (-o-), efficiency of photo-Fries rearrangement (- -), and absorption spectrum (—A-) of bisphenol-A polycarbonate [34],...
The occurrence of a photo-Fries rearrangement is well established in polycarbonates (cf. section 4.5), which contain very similar structures. [Pg.277]

Scheme 3.22 Photo-Fries rearrangement in the main chain of a polycarbonate. Scheme 3.22 Photo-Fries rearrangement in the main chain of a polycarbonate.
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