CAREER: Effect of Electric Fields on the Miscibility of Polymer Blends and Block Copolymers

技术概述：目前材料科学的一个主要目标是创造不同混合成分的纳米结构形态。例如，人们认为，在电池和太阳能电池等能源相关应用中，离子和激子的传导效率可以通过调整纳米级聚合物结构域的形态来形成传导途径或通道来优化。实现这种理想形态的一种途径是通过电场的应用来对齐微畴，这对于电极已经是设备一部分的应用特别有利。目前，人们对电场的存在如何影响聚合物共混物和嵌段共聚物的混相的理解仍然有限。特别地，由电场引起的自由能对混合的贡献是什么？这种现象的理论受到缺乏明确的实验数据的限制，这些数据可以相当大，在电场强度约为10 V/微米时，相分离温度可降低50 K。提出的研究将使用荧光来测量聚合物共混物的相分离温度和嵌段共聚物的有序-无序转变温度作为电场存在下组成的函数。实验结果将适合于修正的弗洛里-哈金斯表达式，以确定由电场的存在引起的混合的自由能贡献。这些结果将提高对控制混相的聚合物-聚合物相互作用的基本理解，并提供一种局部调节和控制共混物的焓相互作用的方法。非技术总结：聚合物在技术先进的应用中应用广泛，其中许多应用使用多种聚合物组件排列成纳米级结构域。这些畴的排列可以通过在器件的现有电极上施加电场来优化。PI将对电场的存在如何影响聚合物中的混合相互作用产生基本的理解，这是一种目前尚不清楚的现象。教育部分将开发一个指导资源网络，提供实用的职业建议。活动的核心将是一个基于网络的讨论论坛，所有年龄段和各行各业的学生都可以在这里就潜在的职业规划和实现目标的第一手经验交换意见。这样的场所将有助于填补目前缺乏的实用职业信息的空白。这对于经济背景有限的学生尤其重要，这些学生通常来自代表性不足的少数民族，他们通常没有从事相关职业的亲戚或家庭朋友可以提供所需的指导。该计划将直接激励不同层次的学生寻找就业机会，带领研究生和本科生参观当地公立学校，分享他们对科技事业的抱负。

TECHNICAL SUMMARY:A major materials science objective at present is to create nanostructured morphologies of different blend components. For example, it is believed that the efficiency of ion and exciton conduction in energy related applications such as batteries and solar cells may be optimized by adjusting the morphology of the nanometer-sized polymer domains to form conducting pathways or channels. One route to such ideal morphologies is through alignment of microdomains via the application of electric fields, particularly advantageous for these applications where electrodes are already part of the device. Currently there is still limited understanding of how the presence of electric fields affects the miscibility of polymer blends and block copolymers. In particular, what is the free energy contribution to mixing caused by the presence of an electric field? Theory of this phenomenon is limited by a lack of unambiguous experimental data characterizing the shifts in miscibility with electric fields, which can be quite large, up to 50 K decrease in the phase separation temperature for field strengths around 10 V/micrometer. The proposed research will use fluorescence to measure the phase separation temperature of polymer blends and the order-disorder transition temperature of block copolymers as a function of composition in the presence of electric fields. The experimental results will be fit to a modified Flory-Huggins expression to ascertain the free energy contribution to mixing caused by the presence of an electric field. These results will provide improved fundamental understanding of the polymer-polymer interactions that control miscibility and a means to locally tune and control the enthalpic interaction of a blend. NON-TECHNICAL SUMMARY:Use of polymers in technologically advanced applications is widespread, with many of these applications using multiple polymer components arranged into nanometer-sized domains. The alignment of these domains could be optimized by the application of electric fields across the existing electrodes of the device. The PI will develop a fundamental understanding of how the presence of electric fields affects the blending interactions in polymers, a phenomenon which is currently not understood. The educational component will develop a network of mentoring resources for practical career advice. The centerpiece will be a web-based discussion forum where students of all ages and walks of life can exchange advice on potential career plans and first-hand experience in ways of accomplishing their goals. Such a venue will help fill a void in practical career information that is currently lacking. This is especially important for students from economically limited backgrounds, most frequently from underrepresented minorities, who typically do not have relatives or family friends in related careers that can provide the needed guidance. The PI will directly motivate students at a range of levels about career opportunities, taking groups of graduate and undergraduate students to visit local public schools to share their aspirations about careers in science and technology.