Do impurity chromophores affect the tunneling dynamics of an amorphous polymer? Investigation by single-molecule spectroscopy

• Published in: Molecular physics 2009-09, Vol.107 (18), p.1943-1953
• Main Authors: Yu. Eremchev, I., Naumov, A.V., Gorshelev, A.A., Vainer, Yu. G., Kador, L., Köhler, J.
• Format: Article
• Language: English
• Subjects: low-temperature glass dynamics; single-molecule spectroscopy; tunneling two-level systems
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268970802672676

This work is devoted to the study of a key question of impurity-center spectroscopy: the influence of probe molecules on the local dynamics of the matrix. The main idea of our studies was to compare, on the single-molecule level, the spectral dynamics of an amorphous matrix (polyisobutylene (PIB)) as measured with different dopants (tetra-tert-butylterrylene (TBT), dibenzo-anthanthrene (DBATT), and a calixarene bearing two perylene bisimide dyes (di-PBI)). The study was based on the statistical analysis of the parameters of a number of single-molecule spectra. We found that, at T < 2 K, the tunneling dynamics of PIB doped with TBT and DBATT is similar, indicating negligible influence of these molecules on the matrix dynamics, whereas the dynamics observed in PIB doped with di-PBI is markedly different. This is most probably related to the different polarities and geometries of the probe molecules: TBT and DBATT are non-polar, whereas di-PBI dimers are polar, have a larger size, and are characterized by two large chromophore groups.