Degradation of poly

The preceding results on polycarbonate are at variance with the ultrasonic degradation of poly(vinyl pyrollidone) prepared with peroxide linkages where the rate of chain cleavage was determined to be 5000 times faster at the — 0 — 0 — than the — C —C— bonds [164]. 

Bowmer and Bowden75 studied the radiation degradation of poly-2-methyl-l-pentene sulfone and found that at low radiation doses the S02/olefin ratio is 2 1, however at high doses this ratio is decreased and is close to unity. Thus the oligomerization of the olefin, which is the cause for the discrepancy between G(S02) and G(olefin), appears to be reversible. 

FIGURE 8. Overall reactions scheme for radiation degradation of poly(olefin sulfone)s. Reproduced by permission of the authors from Reference 74. 

However, Pacansky and his coworkers77 studied the degradation of poly(2-methyl-l-pentene sulfone) by electron beams and from infrared studies of the products suggest another mechanism. They claim that S02 was exclusively produced at low doses with no concomitant formation of the olefin. The residual polymer was considered to be essentially pure poly(2-methyl-l-pentene) and this polyolefin underwent depolymerization after further irradiation. However, the high yield of S02 requires the assumption of a chain reaction and it is difficult to think of a chain reaction which will form S02 and no olefin. 

Deschamps AA, van Apeldoom AA, Hayen H, et al. In vivo and in vitro degradation of poly(ether ester) block copolymers based on poly(ethylene glycol) and poly (butylene terephthalate)[J]. Biomaterials, 2004, 25, 247-258. 

Figure 2 Hydrolytic degradation of poly(phosphoester-urethanes) based on TDI.

Fig. 1. The metabolic cycle for the synthesis and degradation of poly(3HB). (1) 3-ketothiolase (2) NADPH-dependent acetoacetyl-CoA reductase (3) poly(3HB) synthase (4) NADH-dependent acetoacetyl-CoA reductase (5), (6) enolases (7) depolymerase (8) d-(-)-3-hydroxybutyrate dehydrogenase (9) acetoacetyl-CoA synthetase (10) succinyl-CoA transferase (11) citrate synthase (12) see Sect. 3...

The mechanism of the intracellular degradation of poly(HA) by bacteria, i.e., the mobilization of a previously accumulated polyester, is poorly understood (see also the chapter by Babel et al. in this book). Most of the research on intracellular poly(3HB) mobilization was done more than 30 years ago. Lemoigne observed in 1925 that 3-hydroxybutyrate was the main product of anaerobic breakdown of poly(3HB) in Bacillus M [12,137]. Macrae and Wilkinson [138, 139] noticed a reduction of the poly(3HB) content of Bacillus megaterium upon aerobic incubation of poly(3HB)-rich cells in phosphate buffer. The authors found that autolysis of poly(3HB)-rich cells occurred later and to a minor extent compared to poly(3HB)-poor cells and proposed that poly(3HB) might... 

Obst M, Steinbuchel A (2004) Microbial degradation of poly(amino acid)s. Biomacromolecules 5 1166-1176... 

Fortin, J. B. Lu, T. M., Ultraviolet radiation induced degradation of poly para xylylene (parylene) thin films, Thin Solid Films 2001, 397, 223 228... 

Allen, N. S., Edge, M., Mohammadian, M. and Jones, K., UV and thermal hydrolytic degradation of poly (ethylene terephthalate) importance of hydroperoxides and benzophenone end groups, Polym. Degrad. Stabil., 41, 191-196 (1993). 

Figure 18.12 Effect of fluorescent device exposure on carboxylic acid production in Spectar copolymer as determined by SF4 treatment 1816cm-1, aromatic acid peak 1841 cm1, aliphatic acid peak [11]. Reprinted from Polymer, 41, Grossetete, T., Rivaton, A., Gardette, J.-L., Hoyle, C. E., Ziemer, M., Fagerburg, D. R. and Clauberg, H., Photochemical degradation of poly(ethylene terephtha-late)-modified copolymer, 3541-3554, Copyright (2000), with permission from Elsevier Science...

I. Armentano, M. Dottori, D. Puglia, ).M. Kenny, Effects of carbon nanotubes (CNTs) on the processing and in-vitro degradation of poly(DL-lactide-co-glycolide)/CNT films, Journal of Materials Science-Materials in Medicine, vol. 19, pp. 2377-2387, 2008. 

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