ELECTROCHEMICAL CONTROL OF BLOCK COPOLYMER SELF-ASSEMBLY

摘要通过大量的理论和实验研究，人们已经了解了温度和压力等常规变量对嵌段共聚物自组装的影响。在这个项目中，人们使用电化学势来控制嵌段共聚物纳米结构的形成，这代表了与传统方法的显著偏离，因为这些系统本质上是不平衡的。这项研究的动机是缺乏对电场和软物质自组装之间耦合的基本理解，以及由于电场易于控制和应用而产生的实际优势。感兴趣的系统是含二茂铁的嵌段共聚物。初步数据表明，这些有机金属嵌段共聚物可逆地响应于2 V/cm的电势：有序状态在正极附近是稳定的，无序状态在负极附近是稳定的。这与先前使用电场控制嵌段共聚物自组装的尝试形成鲜明对比，其中需要高达105 V/cm的场来诱导微结构排列的不可逆变化。所需的嵌段共聚物将通过阴离子聚合来合成。链上的一部分二茂铁（Fc）基团在合成后在正常条件下处于不带电状态，在合适的抗衡离子（例如Fc+NO3）存在下将被氧化为二茂铁鎓（Fc+）。聚合物将溶解在电解质中并置于电化学电池中。Fc和Fc+之间的可逆转化以及伴随的电流将用于驱动纳米结构的形成。将通过空间分辨、原位紫外光谱、双折射、小角X射线和中子散射研究各种嵌段共聚物的自组装。将努力识别系统的秩序和无序完全和迅速地响应于所施加的电场的变化。PI自2001年以来一直是伯克利学生多样性和学术发展委员会的成员。1974年，该委员会设立了专业发展计划（PDP），以鼓励来自弱势群体的学生大量参加所有学位课程。PI在Research Advocate（伯克利出版物）上发表了一篇文章，旨在将有兴趣扩大其科学活动影响的教师与PDP运行计划联系起来，这些计划将从他们的参与中受益。为了增加这一建议的更广泛的影响，PI将参加威拉德中学最近成立的PDP运行程序。威拉德45%的学生是非洲裔美国人。在这个项目中，教师和PDP工作人员被邀请到教室了解当前的科学和数学课程，并与教师讨论可能增加的课程。PI将提出基于当前电活性聚合物的演示，以及如何将其用于制造人造肌肉。

ABSTRACTConsiderable theoretical and experimental effort has led to an understanding of the effect of conventional variables such as temperature and pressure on the self-assembly of block copolymers. In this project one uses electrochemical potential to control the formation of block copolymer nanostructures, which represents a significant departure from the conventional approach because these systems are inherently out of equilibrium. This study is motivated by both a lack of fundamental understanding of the coupling between electric fields and self assembly in soft matter, and the practical advantages that arise due to ease with which electric fields can be controlled and applied. The systems of interest are ferrocene containing block copolymers. Preliminary data indicate that these organometallic block copolymers respond reversibly to electric potentials of 2 V/cm: the ordered state is stable near the positive electrode and the disordered stare is stable near the negative electrode. This is in sharp contrast to previous attempts to use electric fields to control block copolymer self assembly wherein fields as high as 105 V/cm are needed to induce irreversible changes in microstructure alignment. The required block copolymers will be synthesized by anionic polymerization. A fraction of the ferrocene (Fc) groups on the chain, which are in the uncharged state under normal conditions after synthesis, will be oxidized to ferrocenium (Fc+) in the presence of a suitable counterion (e.g. Fc+NO3). The polymer will be dissolved in an electrolyte and placed in an electrochemical cell. Reversible transformations between Fc and Fc+ and the concomitant electric current will be used to drive nanostructure formation. The self-assembly of a wide range of block copolymers will be studied by spatially resolved, in situ UV via spectroscopy, birefringence and small angle X-ray and neutron scattering. Efforts will be made to identify systems that order and disorder completely and rapidly in response to changes in the applied electric fields. Broader Impact The PI is a member of the Committee on Student Diversity and Academic Development at Berkeley since 2001. In 1974, the committee established the Professional Development Program (PDP) to encourage students from disadvantaged groups to enroll in all degree programs in substantial numbers. The PI has published an article in Research Advocate (a Berkeley publication) that is aimed at connecting faculty who are interested in broadening the impact of their scientific activities with PDP run programs that would benefit from their participation. To increase the broader impact of this proposal, the PI will participate in a recently established PDP run program at Willard Middle School. 45 % of the students in Willard are African American. In this program, faculty and PDP staff members are invited to the classrooms to learn about the current science and math curriculum, and to discuss possible additions to the curriculum with teachers. The PI will propose demonstrations based on current electro-active polymers, and how this can be used to create artificial muscles.