EAGER: Confined Self Assembly of Fully Conjugated Rod-Rod Diblock Copolymers in Nanofibers

这一早期概念探索性研究补助金(AGER)为研究完全共轭杆-杆两嵌段共聚物的纳米纤维中的受限自组装提供了资金。纳米纤维将通过一种名为静电纺丝的工艺来制造，该工艺使用强大的电场来拉长和细化聚合物溶液喷射，从而能够形成直径接近纳米级(50-500 nm)的纤维。棒棒嵌段共聚物结合了棒状聚合物的液晶有序性(长度为1-10 nm)和线圈-线圈嵌段共聚物的微相分离(长度为10-100 nm)的物理特性，具有形成分级有序材料的潜力。将研究溶剂挥发速率和拉伸变形(在电纺丝过程中)对两个长度尺度上的自组装结构的影响。纳米纤维中的组装将使用透射电子显微镜以及小角和广角X射线散射来表征。关于溶液浇铸薄膜中的自组装的类似研究将作为参考。如果成功，这项工作将为高效有机太阳能电池的设计提供一种新型的活性材料。特别是，共轭聚合物嵌段(具有适当的电子性质)的自组装将在太阳能电池的光吸收活性层中提供电子给体和电子受体材料的周期性界面。这将确保及时解离束缚电子和空穴(在光激发下产生)，这是有效产生光电流所必需的。将完全共轭的棒-棒两嵌段共聚物限制在纳米纤维中将有两个好处。首先，它将提供机会开发一类新的材料，即有机半导体可穿戴面料。其次，在静电纺丝过程中强烈的拉伸变形和快速的溶剂挥发，再加上纳米纤维中的物理圆柱形限制，将提供获得在平衡体系或薄膜中可能无法实现的新型自组装结构的途径。

This EArly-concept Grant for Exploratory Research (EAGER) provides funding to study the confined self assembly in nanofibers of fully conjugated rod-rod diblock copolymers. Nanofibers will be fabricated via a process called electrospinning that uses a strong electric field to elongate and thin a polymer solution jet enabling the formation of fibers with near nanoscale diameters (50-500 nm). Rod-rod block copolymers combine the physics of liquid crystalline ordering of rod-like polymers (at the length scale of 1-10 nm) and microphase-separation of coil-coil block copolymers (at length scale of 10-100 nm) with the potential of forming hierarchically ordered materials. The effects of solvent evaporation rate and extensional deformation (during electrospinning) on self assembly structures at both length scales will be studied. The assembly in nanofibers will be characterized using transmission electron microscopy as well as small and wide angle x-ray scattering. Similar studies on self assembly in solution-cast films will be conducted as reference. If successful, this work will provide a novel active material for the design of high efficiency organic solar cells. In particular, self assembly of conjugated polymeric blocks (with appropriate electronic properties) will provide periodic interfaces of electron donor and electron acceptor materials in the light absorbing active layer of solar cells. This will ensure timely disassociation of bound electron and hole (created on photo-excitation), necessary to produce photocurrent efficiently. Confining fully conjugated rod-rod diblock copolymers within nanofibers will have two benefits. First, it will provide the opportunity to develop a new class of materials, namely, wearable fabrics of organic semiconductors. Secondly, the strong extensional deformation and fast solvent evaporation during electrospinning combined with the physical cylindrical confinement in nanofibers will provide access to novel self assembled structures that may not be possible in equilibrium systems or films.