CAREER: Evaluating Theories of Polymer Crystallization by Directly Calculating the Nucleation Barrier in a Polymer Melt

职业：通过直接计算聚合物熔体中的成核势垒来评估聚合物结晶理论

• 批准号: 2338690
• 负责人: Douglas Tree
• 金额: $ 50.88万
• 依托单位: Brigham Young University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-03-01 至 2029-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2338690&HistoricalAwards=false
• 关键词: CAREER; Evaluating; Theories; Polymer; Crystallization

NONTECHNICAL SUMMARYPolymers are long-chain molecules found in a wide array of natural and man-made materials, ranging from DNA, wood, and rubber to piping, clothing, and grocery bags. Many essential polymer materials have a structure that is at least partially crystalline, meaning the atoms within the molecule arrange themselves regularly in space. Crystallinity plays a crucial role in determining the properties of polymer materials, and thus it is critical that scientists and engineers be able to understand and manipulate how and when polymers crystallize.Despite extensive research, the exact mechanism behind polymers crystallization remains unknown. There are several competing theories, but evidence from experiments and computer simulations has been inconclusive. This project will apply a simulation method that was successfully used to study the crystallization of non-polymers such as water to study polymers. The project objectives will focus on studying how the length of the molecules and the different types of polymers affect the mechanism of crystallization. Success with this new approach could revolutionize our basic understanding of how polymers form crystals, potentially leading to the development of innovative new materials and reduced environmental impacts from existing ones.The project will also include educational objectives that are integrated with research activities. Specifically, the project will create mentoring opportunities between undergraduates and K-12 students, between the PI and undergraduates, between more and less experienced graduate students, and between the PI and future scientists through the creation of a podcast that focuses on career development in the sciences.TECHNICAL SUMMARYDespite decades of research, polymer science lacks a widely accepted theory for crystallization from the melt state. The development of an accurate theory of polymer crystallization would not only change textbooks, but it would also enable the creation of new polymers with better properties and processes for making polymers with less environmental impact.Nucleation processes are foundational to polymer crystallization, but accumulating evidence suggests that Classical Nucleation Theory inadequately explains homogeneous nucleation, leading researchers to propose controversial alternative theories. The central hypothesis of this project is that equilibrium advanced sampling methods can be used to directly calculate the nucleation barrier to test these new theories. While new to polymer crystallization, advanced sampling methods have been used study nucleation in other fields, and they have distinct advantages over other methods. Accordingly, this project will focus on a study of the nucleation barrier for folded-chain crystals as a function of polymer molecular weight and as a function of polymer chemistry. This project will also contribute to the ongoing development of simulation software for computing free energy landscapes in low-temperature polymer melts.The project will also involve integrated research and teaching aims specifically focusing on effective and scalable mentoring opportunities for students spanning from K-12 through graduate education levels. Mentoring new scientists and engineers, especially underrepresented minorities, is a key educational component of cultivating a globally competitive and diverse workforce. Specific mentoring activities include near-peer mentoring and outreach to K-12 students, PI-mentored undergraduate research, scalable mentoring experiences through the production and distribution of the podcast ``How Science Happens,'' and near-peer mentoring of graduate students through a chemical engineering student council.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.

非技术摘要聚合物是在各种天然和人造材料中发现的长链分子，范围从DNA，木材和橡胶到管道，衣服和杂货袋。许多必需的聚合物材料具有至少部分结晶的结构，这意味着分子内的原子定期在太空中排列。结晶度在确定聚合物材料的性质中起着至关重要的作用，因此，至关重要的是，科学家和工程师能够理解和操纵聚合物如何结晶和操纵聚合物。尽管进行了广泛的研究，但聚合物结晶的确切机制仍然未知。有几种相互竞争的理论，但是实验和计算机模拟的证据尚无定论。该项目将采用一种模拟方法，该方法成功地用于研究非聚合物（例如水）的结晶来研究聚合物。项目目标将集中于研究分子的长度和不同类型的聚合物如何影响结晶机理。这种新方法的成功可以彻底改变我们对聚合物如何形成晶体的基本理解，这可能导致创新的新材料的发展，并减少了现有的材料的影响。该项目还将包括与研究活动集成的教育目标。具体而言，该项目将在本科生和K-12学生之间，PI和本科生之间，更多经验丰富的研究生之间以及PI和PI与未来科学家之间的指导机会，通过创建播客，专注于职业发展，该播客的职业发展科学。技术摘要，尽管研究了几十年，所以聚合物科学缺乏从熔体状态下结晶的广泛接受的理论。精确的聚合物结晶理论的发展不仅会改变教科书，而且还可以使创建具有更好的特性和过程的新聚合物，以使环境影响较小的聚合物具有较少的环境影响。经典的成核理论不足以解释均匀的成核，使研究人员提出了有争议的替代理论。该项目的中心假设是，平衡高级抽样方法可用于直接计算成核屏障来检验这些新理论。虽然新的聚合物结晶，但已在其他领域使用了研究成核，并且与其他方法具有不同的优势。因此，该项目将集中于对聚合物分子量的折叠链晶体的成核屏障和聚合物化学的函数的函数。该项目还将有助于持续开发模拟软件，以计算低温聚合物融化中的自由能景观。该项目还将涉及综合研究和教学的目标，专门针对从K-12进行的有效且可扩展的指导机会。研究生教育水平。指导新的科学家和工程师，尤其是代表性不足的少数群体，是培养全球竞争和多样化劳动力的关键教育组成部分。具体的指导活动包括与K-12学生的近乎共进的指导和宣传，通过播客的生产和分发``科学如何发生''，以及通过通过生产和分发来扩展指导经验，以及通过通过化学工程学学生理事会。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估值得支持。