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|Type:||Artigo de periódico|
|Title:||Covalently-attached 1-pyrenylmethyl Groups As A Probe Of Temperature-dependent Relaxation Processes In Polyethylene Films|
|Abstract:||1-Pyrenylmethyl lumophores have been attached covalently to chains of several types of polyethylene (crystallinities 37-74%). The temperature dependence of their fluorescence between 40 and 400 K, as well as that of ultra-high-molecular-weight polyethylene (85% crystallinity) containing covalently-attached 1-pyrenyl groups, has been combined with data from DSC measurements and information concerning the properties of films to determine the utility and limitations of the fluorescence changes to detect the onset temperatures of α-, β- and γ-relaxation processes in the polyethylenes. The relative sensitivities of fluorescence from covalently-attached pyrenyl and anthryl (with a much shorter excited singlet-state lifetime) probes to each of the relaxation processes are compared in the same films. The probe whose excited singlet-state lifetime better matches the rate associated with a relaxation process is better able to detect it.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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