RUI: Metastability of Crystals in Double Crystalline PEO-b-PCL Films and Their Role in Transport Properties

RUI：双晶 PEO-b-PCL 薄膜中晶体的亚稳定性及其在传输性能中的作用

• 批准号: 2004454
• 负责人: Ryan Van Horn
• 金额: $ 26万
• 依托单位: Lafayette College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2004454&HistoricalAwards=false
• 关键词: RUI; Metastability; Crystals; Double; Crystalline

NON-TECHNICAL ABSTRACT:Polymer films are an integral part of technologies in the 21st century. The film’s ability to provide functionality is tied to its physical structure, or arrangement of molecules. For example, degradation of the film is slower in denser areas. Polymers contain some crystals that are denser than the uncrystallized, or amorphous, regions. Controlling the amount and location of the crystalline areas is important for preparing the right material for each application. This research aims to develop structure-property relationships based on the crystallization of the polymer in the film. The amount and size of polymer crystalline aggregates will be controlled by preparing films using different solvents and thermal treatments including preparation temperature or melt-cool cycles. In addition, the crystallinity of the film may change over time; therefore, films will be aged at different temperatures to evaluate whether crystalline content increases or decreases. The crystalline aggregates will be analyzed post-production using spectroscopic and microscopic techniques to learn how the preparation method influenced the crystal development. Once a better understanding of the crystallization behavior is achieved, the film properties, degradation rate, for example, will be tested to see the effect of the tailored changes in crystallization. In addition to scientific discovery, major goals of this research include the training of future scientists and engineers as well as promoting STEM education for underrepresented groups. Undergraduate students will participate in all aspects of the project from lab experiments to public presentation of the results. Performing high-level research helps prepare them for success in graduate school and industrial careers through strong independent thinking and problem solving. Outreach activities will include hosting local high-school students in research and engagement in a K-6 community outreach program that brings students to campus for engineering activities.TECHNICAL ABSTRACT:Poly(ethylene oxide)-block-poly(caprolactone) (PEO-b-PCL) copolymer films are important crystalline polymers for a number of applications. These copolymers serve as model crystalline-crystalline (CC) diblock copolymers with similar melting temperatures. In these copolymers, the crystallization mechanism is complicated, and final crystallinity can be manipulated using solvent interactions and thermal treatment. The manipulation of the crystal structure creates a new thermodynamically stable state within the film. The metastability can be altered with minor changes in state variables, such as temperature and concentration. Additionally, due to the mobile nature of polymer crystal stems, annealing or aging of the films results in a shift from one metastable state to another. It is important to evaluate and understand these changes in metastability to develop reliable structure-property relationships. In PEO-b-PCL, these metastable states are relatively similar, and the interplay of double crystallinity should result in competition between the most stable state for PEO compared to PCL. The goal of this research is to study the metastability of PEO and PCL crystals when the minority block crystallizes first, how aging affects the metastability of each crystal type, and initial correlations between physical structure and macroscopic transport properties like water uptake, degradation, and small-molecule release as models for e.g. drug delivery. By manipulating the physical structure in new ways, changes in the film’s transport properties may open up new avenues for PEO-b-PCL where these characteristics could be tailored to specific applications.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：聚合物薄膜是21世纪技术不可或缺的一部分。这种薄膜提供功能性的能力与其物理结构或分子排列有关。例如，在密度较高的区域，胶片的降解速度会较慢。聚合物含有一些比未结晶或无定形区域更致密的晶体。控制结晶区的数量和位置对于为每种应用准备合适的材料非常重要。本研究的目的是建立基于聚合物在薄膜中结晶的结构-性质关系。聚合物结晶聚集体的数量和大小将通过使用不同的溶剂和热处理来控制，包括制备温度或熔融-冷却循环。此外，薄膜的结晶度可能会随着时间的推移而变化，因此，薄膜将在不同的温度下老化，以评估结晶含量是增加还是减少。晶体聚集体将在生产后使用光谱和显微技术进行分析，以了解制备方法如何影响晶体的发展。一旦对结晶行为有了更好的了解，将测试薄膜的性能，例如降解率，以查看结晶过程中量身定制的变化的效果。除了科学发现，这项研究的主要目标包括培训未来的科学家和工程师，以及促进代表不足的群体的STEM教育。本科生将参与项目的方方面面，从实验室实验到结果的公开展示。进行高水平的研究有助于他们通过强大的独立思考和解决问题的能力，为他们在研究生院和工业职业生涯中的成功做好准备。外展活动将包括接待当地高中生进行研究，并参与K-6社区外展项目，将学生带到校园进行工程活动。技术摘要：聚(环氧乙烷)-嵌段-聚己内酯(PEO-b-PCL)共聚物膜是一种重要的结晶聚合物，具有广泛的应用前景。这些共聚物是具有相似熔化温度的结晶-结晶(CC)两嵌段共聚物模型。在这些共聚物中，结晶机理复杂，最终结晶度可以通过溶剂相互作用和热处理来控制。晶体结构的操纵在薄膜内创造了一种新的热力学稳定状态。亚稳性可以通过温度和浓度等状态变量的微小变化来改变。此外，由于聚合物晶体茎的可移动性，薄膜的退火热处理或老化会导致从一种亚稳态转变为另一种亚稳态。评估和了解亚稳性的这些变化对于发展可靠的结构-性质关系是很重要的。在PEO-b-PCL中，这些亚稳态相对相似，双结晶性的相互作用应该导致PEO和PCL中最稳定的状态之间的竞争。这项研究的目标是研究PEO和PCL晶体在少数块首先结晶时的亚稳性，老化如何影响每种晶体类型的亚稳性，以及物理结构和宏观传输特性(如吸水、降解和小分子释放)之间的初始相关性，作为药物输送的模型。通过以新的方式操纵物理结构，薄膜传输属性的变化可能为PEO-b-PCL开辟新的途径，其中这些特征可以根据特定应用进行量身定做。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。