Dynamic glass transition of the rigid amorphous fraction in polyurethane-urea/SiO2 nanocomposites

Stefanos Koutsoumpis; Konstantinos N Raftopoulos; Oguzhan Oguz; Christine M Papadakis; Yusuf Z Menceloglu; Polycarpos Pissis

doi:10.1039/c7sm00397h

Dynamic glass transition of the rigid amorphous fraction in polyurethane-urea/SiO₂ nanocomposites

Soft Matter. 2017 Jul 14;13(26):4580-4590. doi: 10.1039/c7sm00397h. Epub 2017 Jun 7.

Authors

Stefanos Koutsoumpis¹, Konstantinos N Raftopoulos², Oguzhan Oguz³, Christine M Papadakis⁴, Yusuf Z Menceloglu³, Polycarpos Pissis¹

Affiliations

¹ National Technical University of Athens, Heroon Polytechniou 9, 15780 Zografou, Greece. akoustef@central.ntua.gr.
² Physik-Department, Fachgebiet Physik weicher Materie, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany and Department of Chemistry and Technology of Polymers, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland.
³ Faculty of Engineering and Natural Sciences, Materials Science and Nano Engineering, Sabanci University, 34956, Tuzla, Istanbul, Turkey and Sabanci University Integrated Manufacturing Technologies Research and Application Center & Composite Technologies Center of Excellence, Teknopark Istanbul, 34906, Pendik, Istanbul, Turkey.
⁴ Physik-Department, Fachgebiet Physik weicher Materie, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany.

PMID: 28590480
DOI: 10.1039/c7sm00397h

Abstract

We report molecular dynamics in the rigid amorphous fraction (RAF) of the polymer bound at the interfaces with nanoparticles in polymer nanocomposites and calculate the glass transition temperature, T_g, for this bound layer of polymer. We follow the '3-phase-model' for semicrystalline polymers where the polymer matrix consists of the crystalline fraction (CF), the mobile amorphous fraction (MAF) and the RAF. While the amorphous polymer bound by crystallites is completely rigid, neither contributing to the glass transition, nor displaying molecular dynamics, the amorphous polymer bound at the interfaces with filler displays decelerated dynamics, as compared to the bulk polymer. Reports in the literature suggest a discrepancy between T_g values obtained by Differential Scanning Calorimetry (DSC) and by Dielectric Relaxation Spectroscopy (DRS). As a plausible explanation we suggest that DRS results in T_g values taking into account the bound polymer, whereas DSC does not. For this investigation we use semicrystalline polyurethane-urea/SiO₂ nanocomposites and employ, next to DSC and DRS, SEM, SAXS and WAXS for morphological characterization. It is our intention to use DRS as a tool for investigating the RAF.