EAGER: Fluid-directed Multiscale Assembly of Conjugated Polymers

非技术摘要：在过去的半个世纪里，电子材料改变了我们的生活方式，在接下来的几十年里，它们可能也会彻底改变我们获取能源的方式。然而，目前电子产品的制造过程中，能源和环境成本都很高。相比之下，基于聚合物的电子产品(即使用特殊塑料材料的超薄膜)可以在低温下通过低成本、高通量的方法(如卷对卷打印)从溶液中加工。材料的受控组装及其在加工过程中形态特征的演变方式在电子、制药、食品、精细化学品、能源材料等广泛的领域中发挥着核心作用。该项目中的方法代表了一种通过设计加工过程中使用的流体流动来控制功能材料组装的新方法。利用假设驱动的方法，它的目的是提供关于流体导向组装的新的基本见解和设计规则，这些规则可能会在许多领域产生广泛的影响。计划中的工作将把研究工作与外联和教育活动结合起来。这些活动将包括对高中生的宣传，特别是旨在增加女孩对科学、工程和技术的兴趣和参与。本科生将接受指导，并将为他们的参与设计与定向组装、聚合物结晶和聚合相关的研究项目。此外，该项目还将影响分子固体定向组装基本原理的新课程开发。本课程将为研究生设计，将包括有机半导体和替代能源的模块。技术摘要：实现高性能共轭聚合物半导体的一个关键挑战是在溶液打印过程中将其组装从分子、介观到宏观。为了解决这一挑战，PI提出了一种新的流体导向组装方法来控制印刷共轭聚合物薄膜在多个长度尺度上的形态。她将通过在微流控开槽模版打印平台上设计流体流动来实现这一方法。具体地说，在分子尺度上，目的是通过引入伸展流动来促进聚合物成核和预聚集，从而在分子聚集体中诱导局部有序化。在介观尺度上，目标是通过设计剪切流来控制聚合物预聚体的取向和排列。PI将进一步研究分子刚性在流动诱导聚合物结晶中的作用，并建立半导体聚合物中形态和电荷传输之间的关系。所提出的方法将结合聚合物结晶和聚集实验、流体流动模拟和流体-聚合物相互作用理论来实现。这种方法可以实现跨多个长度尺度的定向分子组装。一次实现多尺度组装是极具挑战性的，但对于控制固态特性至关重要，例如在印刷电子产品的情况下。此外，所提出的方法将有助于解开半导体聚合物的形态-电荷传输关系。由于缺乏系统地调节多个长度尺度上的薄膜形态的方法，建立这种关系一直是具有挑战性的。

NON-TECHNICAL SUMMARY:Over the past half century electronic materials have changed the way we live, and in the coming decades they may revolutionize the way we harvest energy as well. However, electronic products are presently manufactured by processes of high energy and environmental cost. In comparison, polymer-based electronics (i.e., using ultra-thin films of specialty plastic materials) can be processed from solutions at low temperatures by low-cost, high-throughput methods such as roll-to-roll printing. Controlled assembly of materials and the way their morphological features evolve during processing has played a central role in a broad range of areas ranging from electronics, pharmaceuticals, food, fine chemicals, energy materials, etc. The approach in this project represents a new methodology for controlling assembly of functional materials by designing the fluid flow used in their processing. Using a hypothesis-driven approach, it is aimed at providing new fundamental insights and design rules on fluid-directed assembly that could have broad implications across numerous areas.The planned work will integrate research efforts with outreach and educational activities. These activities will include outreach to high-school students, aiming particularly to increase the interest and participation of girls in science, engineering, and technology. Undergraduate students will be mentored and research projects pertinent to directed assembly and polymer crystallization and aggregation will be designed for their engagement. Also, this project will impact new course development on fundamental principles of directed assembly of molecular solids. The course will be designed for graduate students and will include modules on organic semiconductors and alternative energy.TECHNICAL SUMMARY:A key challenge in realizing high-performance conjugated-polymer based semiconductors is to direct their assembly from molecular, meso-, to macroscale during the solution printing process. To address this challenge, the PI proposes a new method of fluid-directed assembly to control the morphology of printed conjugated-polymer thin films across multiple length scales. She will implement this methodology by designing the fluid flow on the platform of microfluidic slot-die printing. Specifically, at the molecular scale the aim is to induce local ordering in molecular aggregates by introducing extensional flow to promote polymer nucleation and pre-aggregation. At the mesoscale the objective is to control orientation and alignment of polymer pre-aggregates by designing the shear flow. The PI will further investigate the role of molecular rigidity in flow-induced polymer crystallization and establish the relationship between morphology and charge transport in semiconducting polymers.The proposed approach will be implemented by combining experiments on polymer crystallization and aggregation, simulations of fluid flow, and theory on fluid-polymer interactions. This approach can enable directed molecular assembly across multiple length scales. Attaining multiscale assembly at once is highly challenging but critical to controlling solid-state properties, such as in the case of printed electronics. Furthermore, the proposed approach will help to unravel the morphology-charge transport relationships for semiconducting polymers. Establishing this relationship has been challenging due the lack of methodologies for systematically tuning the thin film morphology across multiple length scales.