CAREER: Superelastic Organic Semiconductors (SOSs): A New Class of Molecular Crystals of Responsive Shape Memory

这项学院早期职业发展(Career)补助金将促进对新型超弹性有机半导体(SOSS)响应形状记忆效应的基本了解。形状记忆效应可以通过材料通过热和机械输入记住和恢复编程的形状的能力来说明。超弹性是指材料在给定温度下恢复大量机械变形的能力。有机晶体中的超弹性--通过相互转换的相变--是最近发现的一种材料现象。这一发现将可能孕育分子晶体多晶化工程的新研究领域，为克服可变形电子中有机晶体固有的脆性(脆性)提供一种方法。多晶性是指一种材料在一种以上的晶体结构中存在的能力(有序的分子排列)。该奖项探索了这些结构状态与超弹性、铁弹性和形状记忆功能之间的基本关系。以SOSS为有源层的电子器件无需额外的电路即可响应环境刺激，在遥感、存储器件、可编程电子学等领域具有广泛的应用前景。当涉及到其机械和热可调的电学和光学特性时，SoS也很耐人寻味。随着创造新形式的电子和光学设备的潜力的出现，理解和合理化超弹性有机半导体的机制至关重要。本研究将从理论和实验两方面分析有机半导体在机械和热载荷作用下的形变和形状记忆特性，并进一步了解有机半导体的力学、热学和光电特性之间的基本关系。这项研究将利用基于新课程开发的教育和推广活动，整合数据科学，通过与普渡大学女性工程项目的现有合作为K-12学生提供工程教育，以及让未被充分代表的群体参与工程科学。研究的具体目标是利用多尺度理论建模和实验方法，了解新一类有机半导体中超弹性、铁弹性和形状记忆效应的力学和分子机制。这项研究将(I)了解固态分子晶体中形变和形状记忆效应背后的协同分子机制，(Ii)了解在热和机械载荷下沿马氏体转变轨迹的热力学、动力学和应力分布，(Iii)了解有机晶体中导致超弹性、铁弹性和形状记忆效应的分子动力学和形变孪晶/去孪晶，以及(Iv)通过了解用于光电子学的SOSS的机械、电子、光学和热学性质来建立结构-性质关系。总体而言，该研究项目旨在解决对宏观和可逆变形的分子结构响应外部刺激的基本理解方面的重大挑战。对有机晶体中超弹性/铁弹性的基本认识将为固体分子中的马氏体相变创造新的知识。这些知识可以为通过分子设计快速、可逆地调制电子和光学特性开辟新的途径。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) grant will promote fundamental understanding of the responsive shape memory effect in a new class of superelastic organic semiconductors (SOSs). The shape memory effect can be illustrated by the ability of a material to remember and recover a programmed shape via thermal and mechanical input. Superelasticity refers to the ability of a material to recover a large amount of mechanical deformation at a given temperature. Superelasticity in organic crystals - through interconvertible phase changes - is a recently discovered materials phenomenon. This discovery will likely breed a new research field on polymorphic engineering of molecular crystals, providing a way of overcoming the intrinsic fragility (brittleness) of organic crystals in deformable electronics. Polymorphism is the ability of a material to exist in more than one crystal structure (ordered molecular arrangement). This award explores the fundamental relationship between those structural states and the functionalities of superelasticity, ferroelasticity, and shape memory. Electronic devices with SOSs as active layers can respond to environmental stimuli without additional circuits and find a variety of applications such as remote sensing, memory devices, and programmable electronics. SOSs are also intriguing when it comes to their mechanically and thermally tunable electrical and optical properties. With the potential to create new forms of electronic and optical devices, it is vital to understand and rationalize the mechanics of superelastic organic semiconductors. This research project will both theoretically and experimentally analyze the deformability and shape memory in organic semiconductors under mechanical and thermal load and further understand the fundamental relationship between the mechanical, thermal, and optoelectronic properties of SOSs. The research will leverage the educational and outreach activities based on new curriculum development integrating data sciences, engineering education for K-12 students through an existing collaboration with Women in Engineering Program at Purdue, and engagement of underrepresented groups in engineering sciences.The specific goal of the research is to understand the mechanics and molecular mechanism of superelasticity, ferroelasticity, and shape memory effect in a new class of organic semiconductors using multi-scale theoretical modeling and experimentation approaches. The research will (i) understand the cooperative molecular mechanism underlying the deformability and shape memory effect in the solid-state molecular crystal, (ii) understand the thermodynamics, kinetics, and stress profiles along the trajectory of the martensitic transition under the thermal and mechanical load, (iii) understand the molecular kinetics and deformation twinning/detwinning in organic crystals responsible for the superelasticity, ferroelasticity, and shape memory effect, and (iv) establish the structure-property relationship by understanding the mechanical, electronic, optical, and thermal properties of SOSs for the use in optoelectronics. Overall, the research project is to address a grand challenge in the fundamental understanding of molecular structures of macroscopic and reversible deformation in response to external stimuli. The fundamental understanding of superelasticity/ferroelasticity in organic crystals will create new knowledge about the martensitic phase transition in solid-state molecules. Such knowledge can open new avenues for rapid, reversible modulation of electronic and optical properties by means of molecular design.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.