Degradation of aromatic polymers—III. Crosslinking and chain scission during photodegradation of polysulphones

✍ Scribed by Shin-ichi Kuroda; Ayako Nagura; Kazuyuki Horie; Itaru Mita

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 458 KB
• Volume: 25
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(89)90015-3

✦ Synopsis

Bisphenol A polysulphone (PSF) and polyethersulphone (PESF) were photodegraded homogeneously at room temperature in an inert and a normal atmosphere. The average molecular weights and the molecular weight distributions of degraded samples were measured by means of GPC to evaluate the quantum yields of chain scission and crosslinking. Simultaneous crosslinking and chain scission occur in the photodegradation of PSF and PESF. The ratio of the chain scission rate to the crosslinking rate was found to be 4.5 for PSF and 6.0 for PESF in the early stage of degradation. Quantum yields of crosslinking and chain scission were found to be of the order of 10 -~ tbr PSF as well as PESF and they are not greatly affected by the atmosphere during irradiation. It was also found that deceleration of reaction occurs in the later stages of degradation of both PSF and PESF. Photodegradation through addition to the benzene rings and H-abstraction by phenyl radicals formed by C--S cleavage at diphenylsulphone moieties is proposed. The formation of phenol moieties by the photorearrangement of diphenylether moieties was revealed and related with the deceleration of reactions in the later stages of photodegradation of polysulphones, on the basis of i.r. analysis.