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

探索性研究早期概念基金（EAGER）为研究完全共轭棒-棒二嵌段共聚物在纳米纤维中的自组装提供了资金。纳米纤维将通过一种称为静电纺丝的工艺制造，该工艺使用强电场将聚合物溶液射流拉长并变薄，从而形成接近纳米级直径（50-500纳米）的纤维。棒-棒嵌段共聚物结合了棒状聚合物（长度尺度为1- 10nm）的液晶有序物理特性和线圈-线圈嵌段共聚物（长度尺度为10- 100nm）的微相分离特性，具有形成分层有序材料的潜力。将研究溶剂蒸发速率和拉伸变形（在静电纺丝过程中）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。类似的自组装在溶液铸造薄膜的研究将作为参考。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的活性材料。特别是，共轭聚合物块的自组装（具有适当的电子性质）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。这将确保束缚电子和空穴（在光激发下产生）的及时解离，这是有效产生光电流所必需的。在纳米纤维中限制完全共轭的棒-棒二嵌段共聚物将有两个好处。首先，它将为开发一种新的材料提供机会，即有机半导体的可穿戴织物。其次，静电纺丝过程中的强拉伸变形和快速溶剂蒸发与纳米纤维中的物理圆柱形约束相结合，将提供在平衡系统或薄膜中可能不可能实现的新型自组装结构。

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.