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

非技术概述：聚合物纤维被广泛应用于各种领域，如纺织品。现在，通过一种称为静电纺丝的工艺，已经可以制造出直径极小的聚合物纤维，比人类的头发小得多。制造非常小的纤维的能力是重要的，因为它开辟了在更高级应用中使用的可能性，例如作为提供清洁水的油水分离膜（促进人类福利），或作为辅助神经元等人类细胞生长的支撑（促进人类健康）。该研究项目的第一部分涉及制作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，以发现当它们经历加热时纤维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、融化或完全破裂，这取决于它们经历了多少热量，以及它们被加热的速度。纤维也可能发生积极的变化，比如变得更结实，更不容易断裂，或者对可能攻击它们的化学物质有更强的抵抗力。制备小直径纤维并研究其性能将为优化其结构和性能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。聋人及听障学生实习项目将产生社会效益。该项目将通过增加残疾人参与科学技术的机会，促进科学工作者的多样性，因为残疾人在这些领域的代表性不足。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，将用于电纺丝微米到纳米级纤维的基础研究。这些方法将用于研究纤维的结晶、玻璃态和液态，以及纤维熔化后形成的液滴。候选聚合物具有高于室温的玻璃化转变温度。示例包括尼龙11、聚（对苯二甲酸乙二酯）、聚（对苯二甲酸丁二酯）或聚（乙烯醇），其在熔化温度下降解。技术目标是：1。制备一系列电纺纤维，并研究其热性能与纤维形态和结构的关系；2. 对纤维（包括在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法，以尽量减少降解对热性能的影响；, 3。测量由这些纤维制成的液滴的成核和生长过程，并与块状材料的行为进行比较。晶体，流动非晶和刚性非晶相的数量将从玻璃化转变时的热容增量来评估。通过使用快速扫描方法，将在冷却速率的六个数量级上评估成核和晶体生长的过程。所进行的热分析将提供新的实验方案，并有助于评估半结晶聚合物的快速扫描数据。该研究将通过聋人和重听本科生实习生暑期项目，增加代表性不足群体，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，例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.