Thermal Properties of Electrospun Fibers, with Research Opportunities for Deaf and Hard of Hearing Interns

非技术概述：聚合物纤维广泛应用于纺织等领域。现在，通过一种名为静电纺丝的工艺，已经有可能制造出直径极小、比人的头发小得多的聚合物纤维。制造超细纤维的能力非常重要，因为它为更先进的应用开辟了可能性，例如用作提供清洁水的油水分离膜(促进人类福祉)，或作为支持神经元等人类细胞生长的支撑物(促进人类健康)。研究项目的第一部分涉及制造小直径聚合物纤维并表征其性能。下一部分涉及加热这些小直径纤维，以发现当它们受热时纤维的结构会发生什么变化。例如，一些纤维在加热时可能会收缩、扭曲、熔化或完全解体，这取决于它们所经历的热量和加热的速度。纤维中也可能发生积极的变化，例如变得更坚固，不太可能断裂，或者对可能攻击它们的化学物质产生更强的抵抗力。制造小直径纤维并研究这些性能将为优化其结构和性能以用于其预期的应用提供重要的基础信息。拟议的研究还将为研究生和本科生提供教育和培训。社会福利将从聋哑生实习计划中受益。该方案将通过增加残疾人对科学和技术的参与，促进科学工作者的多样性，残疾人属于这些领域中代表性不足的群体。技术概述：先进的热分析方法，如温度调制和快速扫描芯片量热法，将被用于微米到纳米级纤维的电纺基础研究。这些方法将被用来研究纤维的结晶，以及纤维的玻璃和液体状态，以及熔化纤维产生的液滴。候选聚合物的玻璃化转变温度将高于室温。例如尼龙11、聚对苯二甲酸乙二酯、聚对苯二甲酸丁二醇酯或聚乙烯醇，它们在熔融温度下会降解。技术目标是：1.制备一系列电纺纤维，并研究与纤维形态和结构有关的热性能；2.对纤维，包括玻璃化转变温度以上降解的聚合物，使用快速扫描芯片量热仪，以最大限度地减少降解对热性能的影响；以及，3.测量由这些纤维制成的液滴中的成核和生长过程，并与大块材料中的行为进行比较。晶相、可移动非晶相和刚性非晶相的数量将由玻璃化转变时的热容增量来估算。通过使用快速扫描方法，将在冷却速度的六个数量级上评估成核和晶体生长过程。所进行的热分析将提供新的实验方案，并有助于评估来自半结晶聚合物的快速扫描数据。这项研究将通过聋哑人本科生实习生暑期计划，增加代表不足的群体，特别是残疾人在STEM领域的参与。通过合作项目，将研究更多应用用途的纤维，如用于油水分离的纤维，或用于引导神经元生长的定向纤维。

NON-TECHNICAL SUMMARY:Polymer fibers are used in a wide variety of applications such as textiles. Now, through a process called electrospinning, it has become possible to make polymer fibers with extremely small diameters, much smaller than a human hair. Ability to create very small fibers is significant because it opens up the possibility for use in more advanced applications, for example as oil-water separation membranes for provision of clean water (promoting human welfare), or as supports to assist the growth of human cells like neurons (promoting human health). The first part of the research project involves making small diameter polymer fibers and characterizing their properties. The next part involves heating these small diameter fibers to discover what changes will occur in the structure of the fibers when they experience heating. For example, some fibers when they are heated may shrink, twist up, melt, or completely fall apart, depending upon how much heat they experience, and how fast they are heated up. There are also positive changes that may occur in the fibers, such as becoming stronger and less likely to break, or developing more resistance to chemicals which could attack them. Making small diameter fibers and studying these properties will provide important fundamental information to optimize their structure and behavior for use in their intended applications. The proposed research also will provide education and training to graduate and undergraduate students. Societal benefit will be derived from the internship program for deaf and hard of hearing students. This program will contribute to improving the diversity of the scientific workforce, by increasing the participation in science and technology of persons with disabilities, who belong to a group under-represented in these fields. TECHNICAL SUMMARY:Advanced methods of thermal analysis, such as temperature modulated and fast scanning chip calorimetry, will be used for fundamental studies of electrospun micron to nanoscale fibers. These approaches will be used to study crystallization, and the glass and liquid states, of fibers and droplets made from melting the fibers. Candidate polymers will have glass transition temperatures above room temperature. Examples include nylon 11, poly(ethylene terephthalate), poly(butylene terephthalate), or, poly(vinyl alcohol), which degrades at its melting temperature. The technical objectives are to: 1. prepare an array of electrospun fibers, and investigate thermal properties in relationship to fiber morphology and structure; 2. use fast scanning chip calorimetry on fibers, including polymers that degrade above their glass transition temperatures, to minimize effects of degradation on thermal properties; and, 3. measure nucleation and growth processes in droplets made from these fibers, and compare with behavior in bulk materials. The amounts of crystal, mobile amorphous, and rigid amorphous phases will be evaluated from the heat capacity increment at the glass transition. By using the fast scanning approach, the process of nucleation and crystal growth will be evaluated over six orders of magnitude in the cooling rate. The thermal analysis undertaken will provide new experimental protocols and aid in the evaluation of fast scanning data from semicrystalline polymers. The research will increase the participation in STEM fields of under-represented groups, especially persons with disabilities, through the summer program for deaf and hard of hearing undergraduate interns. Through collaborative projects, fibers for more applied uses will be studied, such as fibers for oil-water separation, or oriented fibers for guided growth of neurons.