Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Interfaces and Thin Films I

CPP 14.9: Vortrag

Montag, 12. März 2018, 17:15–17:30, C 264

Unexpected behavior of thin PVME/PS blend films investigated by specific heat spectroscopy — •Paulina Szymoniak, Sherif Madkour, and Andreas Schönhals — BAM Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin (Germany)

The structure and molecular dynamics of thin polymer films are of topical interest of soft matter-physics. Commonly, spatial structural heterogeneities of 1D confined thin films (surface, bulk-like and adsorbed layer), are expected to alter the glassy dynamics, compared to the bulk. Here, Specific Heat Spectroscopy (SHS) was used to investigate the glassy dynamics of thin films of an asymmetric miscible PVME/PS 25/75 wt% blend. SHS measurements showed a non-monotonous thickness dependence of the dynamic Tg, on the contrary to the previously investigated PVME/PS 50/50 wt% [1]. For PVME/PS 25/75 wt% thin films (> 30 nm), due to the presence of PVME-rich adsorbed and surface layers, the bulk-like layer experienced a thickness dependent increase of PS concentration. This led to a systematic increase of dynamic Tg. Further decrease of the film thickness (< 30 nm) resulted in a decrease of dynamic Tg, ascribed to the influence of the surface layer, which has a high molecular mobility. This is the first study, which shows deviations of dynamic Tg of thin films, compared to the bulk, resulting from the counterbalance of the influence of the surface and adsorbed layer [2,3]. [1] Yin, H. et al. Macromolecules 2015, 48, 4936. [2] Madkour, S. et al. J. Chem. Phys. 2017, 146, 203321. [3] Madkour, S. et al. ACS Macro Lett. 2017, 6, 1156.