Lenjani Shayan Vazirieh, Zerson Mario, Wang Qian, Sommer Michael, Magerle Robert
Chemische Physik, Institut für Physik, Technische Universität Chemnitz, Reichenhainerstr. 70, 09126 Chemnitz, Germany.
Polymerchemie, Institut für Chemie, Technische Universität Chemnitz, Straße der Nationen 62, 09111 Chemnitz, Germany.
ACS Macro Lett. 2019 Dec 17;8(12):1611-1616. doi: 10.1021/acsmacrolett.9b00722. Epub 2019 Nov 22.
Lyotropic liquid crystalline (LC) phases offer a means of controlling molecular order and orientation in thin films of conjugated polymers. Surface energy, surface-induced ordering, and film thickness are additional factors determining the molecular order in thin films. Through solvent vapor annealing and atomic force microscopy in the swollen state, we show that in ultrathin films of a poly(dithiazolyldiketopyrrolopyrrole-tetrafluorobenzene) (PTzDPPTzF4) alternating copolymer stacks of monomolecular-thick layers with a 2.1 nm step height form, which resemble a lyotropic smectic LC phase. Within the smectic layers, the polymer backbones are aligned parallel to the film plane, with edge-on oriented diketopyrrolopyrrole (DPP) cores. Thicker films resemble a semicrystalline morphology with lamellae consisting of blocks. Such lamellae are typical for polymers crystallizing via Strobl's block-forming model. Our findings indicate that molecular order, molecular orientation, and the morphology of PTzDPPTzF4 copolymer films are tunable by LC order and by varying the film thickness according to the desired application of the particular organic electronic devices.
溶致液晶（LC）相提供了一种控制共轭聚合物薄膜中分子排列和取向的方法。表面能、表面诱导有序化和膜厚度是决定薄膜中分子排列的其他因素。通过溶剂蒸汽退火和处于溶胀状态的原子力显微镜，我们表明，在聚（二噻唑基二酮吡咯并吡咯 - 四氟苯）（PTzDPPTzF4）交替共聚物的超薄膜中，形成了具有2.1 nm台阶高度的单分子层厚层堆叠，类似于溶致近晶LC相。在近晶层内，聚合物主链平行于膜平面排列，二酮吡咯并吡咯（DPP）核为边缘取向。较厚的薄膜呈现出由嵌段组成的片晶的半结晶形态。这种片晶是通过施特罗布的嵌段形成模型结晶的聚合物所特有的。我们的研究结果表明，根据特定有机电子器件的预期应用，PTzDPPTzF4共聚物薄膜的分子排列、分子取向和形态可通过LC有序化以及改变膜厚度来调节。
