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CAREER: Chirality and Polymer Thermodynamics: Frustration and Amplification

职业：手性和聚合物热力学：挫败和放大

基本信息

批准号：
2144511
负责人：
Poornima Padmanabhan
金额：
$ 47.85万
依托单位：
Rochester Institute of Tech
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-07-01 至 2027-06-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2144511&HistoricalAwards=false
关键词：
CAREER Chirality Polymer Thermodynamics Frustration

项目摘要

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2).NONTECHNICAL SUMMARYThis CAREER award supports theoretical and computational research, and integrated education on self-assembly that leads to chiral structures in polymeric materials. Without turning one hand over, one cannot superimpose one’s left-hand over their right one. Atoms or molecules in a material may position themselves so that they may have this same property; the atoms in the material are not in registry with those of the material’s mirror image. The ability to distinguish a material as being either right-handed or left-handed indicates that the material has chirality. Chirality lends itself to specific interactions and novel properties, with applications ranging from selective catalysis, negative refractive index materials, to synthetic life. In chemical systems where complex interactions lead to self-assembly of hierarchical structures at a multitude of length scales, chirality may or may not result in each of those length scales. Numerous examples exist on both sides of the spectrum where chirality at the smaller scale is also exhibited at the larger scale (amplification), or where chirality at the smaller scale does not translate to chirality at the larger scale (frustration).The scientific goal of the project is to enhance the understanding of when and how chirality is transferred from the smallest to the largest length scale by studying the underlying thermodynamic principles and interrogating the molecular-level detail. The systems under consideration are made from polymers, long chain-like molecules made of repeating molecular subunits. Specifically, they are chiral polymers, either studied in isolation, in mixtures, or incorporated into a portion of a longer molecule that has a chiral part and one that is not chiral. A novel particle-based simulation model is developed in this project to measure several thermodynamic properties, including various components of energy and entropy. The use of thousands of molecules also provides insights into the conformations of individual molecules and variations within an individual molecule. Altogether, the project will identify thermodynamic conditions and molecular mechanisms that amplify or frustrate chirality transfer. Such findings can be applied to a variety of self-assembling polymers including synthetic polypeptides and self-assembling foldamers. The education goal of the project is to develop activities and curricula that enhance spatial thinking skill among students at the K-12 and undergraduate levels. Tools such as projections on isometric paper, tactile 3D objects, and visualization software are utilized to support learning. Spatial thinking skills are especially important in the identification of chiral structures, where mental rotations must be performed to identify right-handedness or left-handedness. Such skills not only enhance student performance in structure identification, but also enhance overall performance in STEM-related fields.TECHNICAL SUMMARYChirality is the property where a material cannot be superimposed on its mirror image. This property can not only be exhibited at any length scale, but it can also be exhibited simultaneously at several length scales. For example, in achiral-chiral block copolymers, chirality can be exhibited at the atomic scale, at the conformational scale of a macromolecule, and at the mesoscale. Despite numerous examples of chirality transfer from lower to higher length scales, diverse examples also exist where chirality is limited to a lower length scale alone and does not transfer to a higher length scale. A thermodynamic understanding of conditions when such transfer is amplified, or conditions when such transfer is hindered, remain unknown. Such principles will have implications for the assembly of biomaterials such as synthetic polypeptides and self-assembling foldamers and can be used to answer fundamental questions regarding the origin of life.The scientific goal of the project is to understand the thermodynamic principles and to establish mechanisms that amplify or frustrate chirality transfer in model polymer systems, using particle-based simulations. Specifically, the project develops a tunable and parametrizable model for chiral block copolymers to exhibit conformations that are comparable to experimental measurements. Free energy calculations in the disordered state decouple various thermodynamic contributions, namely, intra- and inter-molecular energies, and entropy arising from conformational changes. To interrogate mechanisms of chiral frustration during self-assembly, the project compares the conformations of the polymers in a lamellar (achiral) structure to that of the ideal scenario. To promote chiral amplification arising from self-assembly, strategies such as nematic ordering through purposefully designed mixtures will be employed. Overall, insights from the project will enable a deeper understanding of the relationship between molecular and structural characteristics.The education goal of the project is to strengthen the spatial thinking skills of students for improved STEM achievement and attainment. Activities are designed for students from diverse backgrounds at the K-12 level and will also be incorporated in the early undergraduate curriculum. Enhancement of spatial thinking skills is anticipated to improve learning gains broadly. Diverse modes of building spatial thinking skills are utilized, including drawings on isometric paper, use of tactile 3-D printed objects, and visualization software. The curriculum developed through this project will benefit students broadly and will fill the current gap in chemical education for identification of chiral structures.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.

该奖项的部分资金来自《2021年美国救援计划法案》(公法117-2)。非技术总结这个职业奖项支持理论和计算研究，以及关于导致聚合物材料手性结构的自组装的综合教育。一只手不翻转，左手就不能叠加在右手上。材料中的原子或分子可以将自己定位为具有相同的性质；材料中的原子与材料镜像中的原子不一致。区分一种物质是右撇子还是左撇子的能力表明该物质具有手性。手性具有特殊的相互作用和新颖的性质，应用范围从选择性催化、负折射率材料到合成生命。在化学体系中，复杂的相互作用导致多个长度尺度上的层次结构的自组装，手性可能会也可能不会导致这些长度尺度中的每一个。在光谱的两边都有许多例子，其中在较小尺度上的手性也在较大尺度上表现出来(放大)，或者在较小尺度上的手性不能转化为在较大尺度上的手性(沮丧)。该项目的科学目标是通过研究基本的热力学原理和询问分子水平的细节来加强对手性何时以及如何从最小尺度到最大长度尺度的理解。正在考虑的系统是由聚合物组成的，聚合物是由重复的分子亚单位组成的长链状分子。具体地说，它们是手性聚合物，要么单独研究，要么混合研究，或者结合到具有手性部分和非手性部分的较长分子的一部分中。本项目开发了一种新的基于粒子的模拟模型来测量几个热力学性质，包括能量和熵的各种分量。数以千计的分子的使用也提供了对单个分子的构象和单个分子内的变化的洞察。总而言之，该项目将确定放大或阻碍手性转移的热力学条件和分子机制。这些发现可以应用于各种自组装聚合物，包括合成多肽和自组装折叠体。该项目的教育目标是开发活动和课程，以加强K-12和本科生的空间思维技能。工具，如在等轴测纸上投影，触觉3D对象，和可视化软件被用来支持学习。空间思维技能在手性结构的识别中尤其重要，在手性结构中，必须进行心理旋转来识别右撇子或左撇子。这些技能不仅提高了学生在结构识别方面的表现，还提高了与STEM相关领域的整体表现。TECHNICAL SUMMARYChirality是指材料不能叠加在其镜像上的属性。这一性质不仅可以在任何长度尺度上表现出来，而且还可以同时在几个长度尺度上表现出来。例如，在非手性-手性嵌段共聚物中，手性可以表现在原子尺度、大分子构象尺度和介观尺度上。尽管手性从较低的标度转移到较高的标度的例子很多，但也存在不同的例子，其中手性仅限于较低的标度而不转移到较高的标度。对于这种转移被放大或被阻碍的情况，热力学上的理解仍然未知。这些原理将对合成多肽和自组装折叠体等生物材料的组装产生影响，并可用于回答有关生命起源的基本问题。该项目的科学目标是了解热力学原理，并利用基于粒子的模拟建立放大或阻碍模型聚合物系统中手性转移的机制。具体地说，该项目为手性嵌段共聚物开发了一个可调和可参数化的模型，以展示与实验测量相当的构象。在无序状态下的自由能计算解耦了各种热力学贡献，即分子内和分子间的能量，以及由构象变化引起的熵。为了探究自组装过程中手性受挫的机制，该项目将聚合物在层状(非手性)结构中的构象与理想情况下的构象进行了比较。为了促进由自组装产生的手性放大，将采用诸如通过有目的地设计的混合物进行向列相排序的策略。总体而言，该项目的见解将使人们更深入地了解分子和结构特征之间的关系。该项目的教育目标是加强学生的空间思维技能，以提高STEM的成绩和素养。活动是为来自不同背景的K-12水平的学生设计的，也将被纳入本科早期课程。空间思维能力的增强有望在更大程度上提高学习成绩。建立空间思维技能的不同模式被利用，包括在等轴测纸上绘图，使用触觉3-D打印物体，以及可视化软件。通过这个项目开发的课程将使学生广泛受益，并将填补目前化学教育中识别手性结构的空白。该奖项反映了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。