Thioxanthone Sensitized Photodegradation of Poly(alkyl methacrylate) Films

Author(s)

Neumann, Miguel G. ^[1] ; Schmitt, Carla C. ^[1] ; Goi, Beatriz E. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Journal of Applied Polymer Science; v. 115, n. 3, p. 1283-1288, FEB 5 2010.
• Web of Science Citations: 5

Abstract

The thioxanthone-sensitized photodegradation of poly(alkyl methacrylate) films {[}alkyl = methyl, ethyl, butyl, and hexyl] was studied using near UV-vis light. The photooxidation process continued even after the total consumption of the sensitizer, possibly due to the excitation of the ketyl groups formed during the first stages of the process. The rate of oxidation, as well as the formation of hydroxy, peroxy, and ketyl groups was faster for polymers with larger ester groups. The decrease of the molecular weight of the degradated polymers was also larger for the hexyl substituted polymer. The side-chain size effect was attributed to the larger amount of secondary hydrogens available for abstraction by the triplet state of thioxanthone, present in the larger ester groups. The lower glass transition temperature of the hexyl substituted polymer allows a better diffusion of oxygen to the deeper layers of the films that also contributes to the faster photodegradation rate. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1283-1288, 2010 (AU)

• FAPESP's process: 03/07770-4 - Interactions of visible light with polymers: photopolymerization and photodegradation
• Grantee: Miguel Guillermo Neumann
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 05/03692-4 - Contributions to the study of the photostability of dyes in polymers
• Grantee: Carla Cristina Schmitt Cavalheiro
• Support Opportunities: Regular Research Grants