Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 58: Nanostructures, Nanostructuring and Nanosized Soft Matter

CPP 58.8: Vortrag

Donnerstag, 4. April 2019, 17:15–17:30, H13

Structural and melting properties of low molecular weight PEG confined in nanoporous ITPC — •Ann-Kathrin Grefe, Björn Kuttich, and Bernd Stühn — Institut für Festkörperphysik, Technische Universität Darmstadt

Ion track-etched polycarbonate constitutes an ideal system for studying confined polymers. Whereas other nanoporous systems often rule out small angle x-ray scattering due to predominant pore scattering and laborious data description, ITPC allows for a more straightforward investigation since the pores are not structurally correlated.^[1]

Nanopores with radii from 8 to 205 nm are prepared and coated with 10 nm of SiO₂ via ALD in order to obtain a well-defined and homogeneous surface. SAXS reveals the nearly perfect cylindrical geometry of the pores. The linear dependency of the pore radius on the etching time is shown to hold true over the complete range of pore radii.

PEG with M_w=1500 g/mol and a semicrystalline lamellar bulk structure is introduced into the nanopores via melt infiltration. At high temperatures SAXS confirms a nearly complete filling with amorphous polymer. Upon cooling below the melting point of PEG, a concentrical arrangement of semicrystalline lamellae is revealed for pore radii over 71 nm. We introduce models which successfully describe the combined scattering from nanopores and semicrystalline or amorphous PEG inside. DSC measurements of the confined polymer show a decrease of melting temperature and heat of fusion per gram polymer upon reduction of the pore radius and hint at a change in nucleation mechanism.

^[1] M. Engel et al., Appl Phys A 97, 99-108 (2009)