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共混组分的纳米结构形态。例如，人们认为，在电池和太阳能电池等与能源相关的应用中，离子和激子的传导效率可以通过调整纳米聚合物结构域的形态来优化，以形成导电路径或通道。获得这种理想形态的一种途径是通过施加电场来对准微区，这对于电极已经是器件一部分的这些应用特别有利。目前，人们对电场如何影响聚合物共混体系和嵌段共聚体系的相容性的认识还很有限。具体地说，电场的存在对混合的自由能贡献是多少？这一现象的理论受限于缺乏明确的实验数据来表征与电场的混溶移动，电场可以相当大，在场强约为10V/微米的情况下，相分离温度降低高达50K。这项研究将利用荧光来测量聚合物共混物的相分离温度和嵌段共聚物在电场作用下的有序-无序转变温度随组成的变化。实验结果将符合修正的Flory-Huggins公式，以确定电场的存在对混合的自由能贡献。这些结果将提供对控制混相性的聚合物-聚合物相互作用的更基本的理解，并提供一种局部调节和控制共混物的焓相互作用的方法。非技术概述：在技术先进的应用中广泛使用聚合物，其中许多应用使用排列成纳米大小的多个聚合物组分。通过在器件的现有电极上施加电场，可以优化这些结构域的对准。PI将从根本上理解电场的存在如何影响聚合物中的混合相互作用，这一现象目前尚不清楚。教育部分将建立一个指导资源网络，提供实用的职业咨询。中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交换关于潜在职业计划的建议和实现目标的第一手经验。这样的场所将有助于填补目前缺乏的实用职业信息空白。这对经济背景有限的学生尤其重要，尤其是来自代表人数不足的少数族裔的学生，他们通常没有亲戚或家庭朋友从事相关职业，无法提供必要的指导。PI将直接激励不同层次的学生了解就业机会，带领研究生和本科生团体参观当地公立学校，分享他们对科技职业的渴望。

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.