End block dynamics in unentangled polymers by dielectric spectroscopy.
| Autor: | Wu M; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States of America., Bichler KJ; Department of Chemistry, Louisiana State University, Baton Rouge, LA, United States of America., Jakobi B; Department of Chemistry, Louisiana State University, Baton Rouge, LA, United States of America., Grzesiowski A; Department of Chemistry, Syracuse University, Syracuse, NY, United States of America., Schneider GJ; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States of America.; Department of Chemistry, Louisiana State University, Baton Rouge, LA, United States of America. |
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| Jazyk: | angličtina |
| Zdroj: | Journal of physics. Condensed matter : an Institute of Physics journal [J Phys Condens Matter] 2023 Jun 15; Vol. 35 (37). Date of Electronic Publication: 2023 Jun 15. |
| DOI: | 10.1088/1361-648X/acdbf7 |
| Abstrakt: | Dielectric spectroscopy measures the dynamics of polymer melts over a broad frequency range. Developing a theory for the spectral shape can extend the analysis of dielectric spectra beyond determining relaxation times from the peak maxima and adds physical meaning to shape parameters determined with empirical fit functions. Toward this goal, we use the experimental results on unentangled poly(isoprene), and unentangled poly(butylene oxide), polymer melts, to test whether the concept of end blocks could be one reason for the Rouse model deviating from experimental data. These end blocks have been suggested by simulations and neutron spin echo spectroscopy and are a consequence of the monomeric friction coefficient depending on the position of the bead in the chain. The concept of an end block is an approximation which partitions the chain in a middle and two end blocks to avoid overparameterization by a continuous position dependent change of the friction parameter. Analysis of dielectric spectra shows that the deviations of the calculated from the experimental normal mode cannot be related to the end block relaxation. However, the results do not contradict an end block hiding below the segmental relaxation peak. It seems that the results are compatible with an end block being the specific part of the sub-Rouse chain interpretation close to the chain ends. (© 2023 IOP Publishing Ltd.) |
| Databáze: | MEDLINE |
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