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|Type:||Artigo de periódico|
|Title:||Investigation of temperature-dependent relaxation processes in polyethylene films by covalently attached anthryl probe|
|Abstract:||The dependence of several aspects of the fluorescence from 9-anthryl groups, covalently attached by tethers of differing lengths to interior sites of five polyolefinic films whose crystallinities range from 0 to 74%, has been explored between 40 and 400 K. The data are employed to determine microscopically the onsets of various relaxation processes of the polymers, the sensitivity of the probes to changes in their local morphologies, and the distribution of the groups between amorphous and interfacial sites. The results are compared with those from noncovalently attached (doped) 9-methylanthracene molecules. Specifically, the relationship between the lengths of tethers for the 9-anthryl groups, as well as the chemical method by which each tether is attached to the polymer chains, and the ability of the fluorescence from the lumophores to detect the onsets of host relaxation processes are explored. The two attachment methods lead to different distributions of lumophores in the amorphous and interfacial regions of the polymers. Furthermore, very short (one atom; methylene) and very long (12 atoms) tethers allow the 9-anthryl groups to sense changes in the local environments more acutely than a tether of intermediate length (three atoms). The advantages of covalent attachment for this sort of study (specifically, the inability of the probe to diffuse within a film from site-to-site with time) and the limitations of the utility of the data are discussed.|
|Editor:||Amer Chemical Soc|
|Citation:||Macromolecules. Amer Chemical Soc, v. 36, n. 10, n. 3485, n. 3497, 2003.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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