Perylene-based profluorescent nitroxides for the rapid monitoring of polyester degradation upon weathering: an assessment

Sylvester, Paul D., Ryan, Helen E., Smith, Craig D., Micallef, Aaron S., Schiesser, Carl H. and Wille, Uta (2013) Perylene-based profluorescent nitroxides for the rapid monitoring of polyester degradation upon weathering: an assessment. Polymer Degradation and Stability, 98 10: 2054-2062. doi:10.1016/j.polymdegradstab.2013.07.006

Author Sylvester, Paul D.
Ryan, Helen E.
Smith, Craig D.
Micallef, Aaron S.
Schiesser, Carl H.
Wille, Uta
Title Perylene-based profluorescent nitroxides for the rapid monitoring of polyester degradation upon weathering: an assessment
Journal name Polymer Degradation and Stability   Check publisher's open access policy
ISSN 0141-3910
Publication date 2013-10
Year available 2013
Sub-type Article (original research)
DOI 10.1016/j.polymdegradstab.2013.07.006
Open Access Status
Volume 98
Issue 10
Start page 2054
End page 2062
Total pages 9
Place of publication London, United Kingdom
Publisher Elsevier
Collection year 2014
Language eng
Abstract A profluorescent nitroxide possessing an isoindoline nitroxide moiety linked to a perylene fluorophore was developed to monitor radical mediated degradation of melamine-formaldehyde crosslinked polyester coil coatings in an industry standard accelerated weathering tester. Trapping of polyester-derived radicals (most likely C-radicals) that are generated during polymer degradation leads to fluorescent closed-shell alkoxy amines, which was used to obtain time-dependent degradation profiles to assess the relative stability of different polyesters towards weathering. The nitroxide probe couples excellent thermal stability and satisfactory photostability with high sensitivity and enables detection of free radical damage in polyesters under conditions that mimic exposure to the environment on a time scale of hours rather than months or years required by other testing methods. There are indications that the profluorescent nitroxide undergoes partial photo-degradation in the absence of polymer-derived radicals. Unexpectedly, it was also found that UV-induced fragmentation of the NO-C bond in closed-shell alkoxy amines leads to regeneration of the profluorescent nitroxide and the respective C-radical. The maximum fluorescence intensity that could be achieved with a given probe concentration is therefore not only determined by the amount of polyester radicals formed during accelerated weathering, but also by the light-driven side reactions of the profluorescent nitroxide and the corresponding alkoxy amine radical trapping products. Studies to determine the optimum probe concentration in the polymer matrix revealed that aggregation and re-absorption effects lowered the fluorescence intensity at higher concentrations of the profluorescent nitroxide, but too low probe concentrations, where these effects would be avoided, were not sufficient to trap the amount of polyester radicals formed upon weathering. The optimized experimental conditions were used to assess the impact of temperature and UV irradiance on polymer degradation during accelerated weathering.
Keyword Profluorescent nitroxide
Melamine-formaldehyde crosslinked
Radical degradation
Accelerated weathering
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

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Created: Tue, 13 Aug 2013, 11:51:25 EST by Sandrine Ducrot on behalf of Centre for Advanced Imaging