Confinement in Electrospun Polymer-Based Nanocomposites, with Research Opportunities for Deaf and Hard of Hearing Interns

技术综述：利用静电纺丝(ES)技术加工纳米纤维，将研究限制对基本物理和结构性能的影响。限制是指通过在纤维内部增加固定的屏障而对聚合物链的流动性造成的限制。除了聚合物的晶体，添加剂，如碳纳米管，有机改性硅酸盐，或二氧化硅，导致纳米复合材料的形成，在这些纳米复合材料中，这些纳米薄膜也作为固定屏障导致链限制。纳米复合材料的松弛性能被改变，从而导致性能的有益改善，例如，使用温度的增加，以及机械模数的增加。将研究ES聚合物基纳米复合材料的相结构和物理性能，因为它们与纤维取向、结晶度、填料类型和用量有关。其目的是：1.通过准等温热容量分析和快速扫描芯片热分析的新方法，对晶体或纳米填料与半结晶电纺纳米复合纤维的非晶态部分之间的关系提供基本的了解；2.将纤维的性质(例如，直径、结晶度、链取向、填料类型、数量和分散度)与约束程度相关联；以及3.将填料的约束作用与晶体的约束作用分开。工作中使用的技术包括通过温度调制差示扫描量热法进行高精度、高精度的热容测量，以量化限制程度。ES纤维的快速扫描芯片量热技术(通过与德国罗斯托克的Schick小组的国际合作)将首次被用于研究ES纤维中的均匀成核。首次将介电弛豫谱(DRS)用于表征ES纤维的偶极驰豫。这些研究将提供一个知识基础，将加强ES纤维材料在重要技术领域的使用，如无纺布纺织品、再生医学以及运输和催化。非技术摘要：通过在含有聚合物和添加剂(如碳纳米管或粘土)的溶液中施加高电场，将使用非常小直径的纤维在纳米尺度上制造非织造薄膜。与传统的大直径纤维相比，用这种方法形成的纳米纤维更坚固，耐热性更强。添加剂的加工条件和性质将有所不同，以确定哪些组合可以产生性能最好的纳米纤维。这些非织造布是用作滤膜、催化、药物输送和智能服装材料组件的候选材料。已经建立了国内和国际合作，使用特殊设备和新的加工条件进行这项研究。为了给残疾学生提供研究机会，四名聋哑人本科生将参加实习，并在夏季几个月进行该项目的研究。这些实习生将学习制造非织造纳米纤维，对其进行热处理，并研究其物理特性。

TECHNICAL SUMMARY:Using the electrospinning (ES) technique for processing nano-scale fibers, the effect of confinement on fundamental physical and structural properties will be investigated. Confinement refers to restrictions on the mobility of the polymer chains brought about by addition of fixed barriers inside the fibers. Besides the crystals of the polymer, additives such as carbon nanotubes, organically modified silicates, or silica, lead to formation of nanocomposites in which these nanofillers also serve as fixed barriers leading to chain confinement. The relaxation properties of the nanocomposite are altered, leading to beneficial improvement of properties, for example an increase in the use temperature, and an increase in the mechanical modulus. The phase structure and physical properties of ES polymer-based nanocomposites will be studied as they relate to the fiber orientation, degree of crystallinity, filler type, and amount. The objectives are to: 1. Provide fundamental understanding about the relationship between crystals or nanofillers and the non-crystalline portions of the semicrystalline electrospun nanocomposite fibers, especially through new methods of quasi-isothermal heat capacity analysis and fast scanning chip calorimetry; 2. Correlate the fiber properties (e.g., diameter, crystallinity, chain orientation, filler type, amount, and dispersion) to the degree of constraint; and 3. Separate the confining effects of the filler from those of the crystals. Techniques to be used in the work include high precision, high accuracy heat capacity measurements by temperature modulated differential scanning calorimetry to quantify the level of confinement. For the first time, the techniques of fast scanning chip calorimetry on ES fibers (through international collaboration with the Schick group in Rostock, Germany) will be applied to study homogeneous nucleation in ES fibers. Also for the first time, dielectric relaxation spectroscopy (DRS) will be used to characterize the dipolar relaxations of ES fibers. These studies will provide a knowledge base which will enhance the use of ES fiber materials in technologically important areas such as non-woven textiles, regenerative medicine, and transport and catalysis.NON-TECHNICAL SUMMARY:Non-woven membranes will be created using very small diameter fibers, on the nano-scale, by applying a high electric field to a solution containing polymer and additives (such as carbon nanotubes or clay). Nanofibers formed this way are stronger and more heat resistant compared to conventional large diameter fibers. The processing conditions and nature of the additive will be varied to see which combinations yield nanofibers with the best properties. These non-woven fabrics are candidate materials for use as filtration membranes, in catalysis, for drug delivery, and as a component of smart clothing materials. Both national and international collaborations have been established for conducting this research using specialty equipment and novel processing conditions. To provide research opportunities for students with disabilities, four deaf and hard of hearing undergraduate students will participate in an internship, and perform research on the project during the summer months. These interns will learn to make the non-woven nanofibers, heat treat them, and study their physical properties.