Dolynchuk Oleksandr, Kahl Robert T, Meichsner Florian, Much Alexander J, Pechevystyi Andrii, Averkova Anna, Erhardt Andreas, Thelakkat Mukundan, Thurn-Albrecht Thomas
Experimental Polymer Physics, Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 3, Halle D-06120, Germany.
Applied Functional Polymers, University of Bayreuth, Universitätsstraße 30, Bayreuth D-95447, Germany.
Macromolecules. 2024 Oct 29;57(21):10399-10409. doi: 10.1021/acs.macromol.4c01819. eCollection 2024 Nov 12.
It has been a long-term goal to understand the molecular orientation in films of conjugated polymers, which is crucial to their efficient exploitation. Here, we show that the surface energies determine the crystal orientation in films of model conjugated polymers, substituted polythiophenes crystallized on substrates. We systematically increase the surface energy of edge-on crystals formed at the vacuum interface by attaching polar groups to the ends of the polymer side chains. This suppresses crystallization at the vacuum interface, resulting in a uniform face-on crystal orientation induced by the graphene substrate in polythiophene films as thick as 200 nm, which is relevant for devices. Surprisingly, face-on crystal orientation is attained in the modified polythiophenes crystallized even on amorphous surfaces. Furthermore, for the samples with still competing interfacial interactions, the crystal orientation can be switched in the same sample, depending on the crystallization conditions. Thus, we report a fundamental understanding and control of the equilibrium crystal orientation in films of conjugated polymers.
理解共轭聚合物薄膜中的分子取向是一个长期目标，这对其有效利用至关重要。在此，我们表明表面能决定了模型共轭聚合物薄膜中的晶体取向，即取代聚噻吩在基底上结晶时的取向。我们通过在聚合物侧链末端连接极性基团，系统地提高在真空界面形成的边对面晶体的表面能。这抑制了在真空界面的结晶，导致在厚度达200 nm的聚噻吩薄膜中由石墨烯基底诱导出均匀的面对面晶体取向，这与器件相关。令人惊讶的是，即使在非晶表面结晶的改性聚噻吩中也能实现面对面晶体取向。此外，对于仍存在竞争界面相互作用的样品，根据结晶条件，同一样品中的晶体取向可以切换。因此，我们报道了对共轭聚合物薄膜中平衡晶体取向的基本理解和控制。
