Molecular dynamics at nanometric length scales

F. Kremer

Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, 04103 Leipzig, Germany

The question on what length-scale molecular and especially glassy dynamics of polymers takes place is of fundamental importance and has multifold practical implications as well. Recent results based on Broadband Dielectric Spectroscopy [1] for nanometric thin (≥5 nm) layers of poly(styrene) [2], poly(cis-1,4-isoprene) [3], poly(styrene‐b‐1,4-isoprene) diblock copolymers [4] and even for isolated chains [5] and for brushes of poly(2-vinylpyridine) in the dried [6] and swollen [7] state will be presented, delivering the concurring result that deviations from glassy dynamics of the bulk never exceed margins of ±3 K independent of the layer thickness, the molecular weight of the polymer under study and the underlying substrate. The experiments lead to the conclusions that glassy dynamics takes place on the length scale a few polymer segments (≤ ~ 1nm), while the conformation of the chain as a whole is strongly modified by the geometrical confinement [8-10]. The results will be discussed with respect to the highly controversial literature [8].

[1] Kremer,F., A. Schönhals (Eds.) Broadband Dielectric Spectroscopy, Springer, Berlin 2003
[2] Tress, M., M. Erber, E.U. Mapesa, H. Huth, J. Müller, A. Serghei, C. Schick, K.-J. Eichhorn, B. Voit and F. Kremer, “Glassy Dynamics and Glass Transition in Nanometric Thin Layers of Polystyrene“, Macromolecules, 43, 9937-9944 (2010)
[3] Tress, M., E.U. Mapesa, W. Kossack, W.K. Kipnusu, M. Reiche, F. Kremer, “Glassy Dynamics in Condensed Isolated Polymer Chains”, Science, 341, 1371-1374 (2013)
[4] Mapesa, E.U., M. Tress, G. Schulz, H. Huth, C. Schick, M. Reiche, F. Kremer “Segmental and chain dynamics in nanometric layers of poly (cis-1,4-isoprene) as studied by Broadband Dielectric Spectroscopy and temperature-modulated Calorimetry”, Soft Matter, 10592-10598 (2013)
[5] Kremer, F. (Ed.) “Dynamics in geometrical confinement”, Advances in Dielectrics, Springer 2014
[6] Kipnusu, W.K., M.M. Elmahdy, E.U. Mapesa, J. Zhang, W. B hlmann, D.-M. Smilgies, C.M. Papadakis, F. Kremer “Structure and Dynamics of Asymmetric Poly(styrene-b-1,4-isoprene) Diblock Copolymer under 1D and 2D Nanoconfinement”, ACS Appl. Mater. Interfaces, 7, 12328-12338 (2015)
[7] Neubauer, N., R. Winkler, M. Tress, P. Uhlmann, M. Reiche, W.K. Kipnusu, F. Kremer, “Glassy dynamics of Poly(2-Vinyl-Pyridine) brushes with varying grafting density”, Soft Matter, 11, 3062-3066 (2015)
[8] Kremer, F., M. Tress, E.U. Mapesa; “Glassy dynamics and glass transition in nanometric layers and films: A silver lining on the horizon”, Journal of Non-Crystalline Solids, 407, 277-283 (2015)
[9] Neubauer, N., M. Tress, R. Winkler, E.U. Mapesa, W.K. Kipnusu, P. Uhlmann, F. Kremer “Molecular Dynamics of Swollen Poly(2-vinylpyridine) Brushes” Macromolecules, 49, 6101-6105 (2016)
[10] Kipnusu W.K., M. Elsayed, R. Krause-Rehberg, F. Kremer; “Glassy dynamics of polymethylphenyl- siloxane in one-and two-dimensional nanometric confinement-a comparison”, J. Chem. Phys. 146, 203302 (2017)