SKM 2021 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: Organic Electronics and Photovoltaics, Electrical and Optical Properties (joint session CPP/KFM)
KFM 11.2: Talk
Thursday, September 30, 2021, 14:00–14:15, H3
On the role of interfaces in controlling the molecular orientation in thin films of polythiophenes — •Oleksandr Dolynchuk1, Philip Schmode2, Matthias Fischer1, Mukundan Thelakkat2, and Thomas Thurn-Albrecht1 — 1Experimental Polymer Physics, Martin Luther University Halle-Wittenberg, Germany — 2Applied Functional Polymers, University of Bayreuth, Germany
Directed crystallization on a substrate is a superior method for inducing crystal orientation in many ordered materials. Although a preferred face-one molecular orientation was evidenced in monolayers of poly(3-hexylthiophene) (P3HT) on graphite, a full face-one orientation in thicker P3HT films has not been realized so far. By using surface-sensitive GIWAXS, here we show that thin films of P3HT crystallized on graphene exhibit a double-layered face-on and edge-on crystal orientation with the latter formed on the top surface [1]. We assume that it is a result of two competing interfacial orientations initiated at the interfaces to graphene and vacuum. By increasing the side-chain polarity in poly[3-(6-bromohexyl)]thiophene, the influence of the interface to vacuum can be reduced, resulting in full face-on orientation in films with a thickness of up to 26 nm [1]. Our findings evidence that directed crystallization can be used to control the orientation of semicrystalline conjugated polymers in thin films if interactions with both interfaces are properly taken into account.
[1] Dolynchuk et al. Macromolecules 2021, 54, 5429-5439.