Growth and Structure of Multifunctional Polymer Brushes from Ultra-thin Coatings

非技术性总结：聚合物刷是长的线状分子，它们与表面化学键合，形成致密、薄的涂层，极大地改变了表面的特性。这些涂层引导再生医学细胞的行为，促进植入设备的生物相容性，抵抗微生物在船体上的沉积，或控制微电子设备中的电流。 聚合物刷的结构提供了形成稳定涂层所需的机械强度，并且它们的化学性质提供了在基底和环境之间进行界面/通信的正确功能。 该研究计划将开发新的合成方法来制造这些聚合物刷，并开发材料表征技术，以促进对所得结构的分子水平理解。这种方法有可能产生广泛的影响，因为化学足够简单，可以被涂料行业所采用。该研究计划将通过REU计划与PI和研究生导师合作，激励和参与本科生进行聚合物科学和工程研究。通过这项研究开发的K-12教育模块将由PI和研究生通过与UW-Madison化学教育研究所（ICE）合作在全国范围内传播。通过妇女在科学和工程（WISE）住宅计划，PI将参与指导代表性不足的学生，通过协调信息，研究和活动，为妇女在科学和工程创造一个支持性的环境。技术摘要：该研究计划将研究合成一个单一的-组分交联的涂层，用于生长均聚物和混合聚合物刷，其对接枝位点的均匀性、分散性、化学官能度、接枝物与接枝物的距离生长低到高分子量的能力，以及对热退火条件的稳定性。从这些涂层的聚合物刷的生长是从根本上不同于从传统的自组装单分子膜的生长。这项研究的一个关键方面将是开发一个机械的理解相结合的深度剖析和角度分辨X射线光电子能谱（ARXPS）的研究的生长过程。 分层效应以及刷生长动力学将作为交联密度和涂层厚度的函数，通过在刷（Br和N）中嵌入特定的元素标记进行研究。 结合ARXPS，原子力显微镜和三维断层扫描将提供有用的形态信息，这些聚合物刷。从这些涂层中生长的刷子将作为“聚合物地毯”从基底上浮起，并通过3D断层扫描获得3D形态学洞察。熔体自洽场理论（SCFT）预测的混合聚合物刷的相图是基于假设的接枝密度是均匀的。到目前为止，满足这些假设的实验手段还很落后。使用独特的化学生长的明确定义的刷和表征方法，在本提案中开发的SCFT预测将进行测试。 此外，化学的简单性预期允许任意改变组成以通过并入适当的共聚单体来调节表面性质。由于这些原因，这里开发的方法有可能通过高度简化聚合物刷的生长方式产生重大影响。

NON-TECHNICAL SUMMARY:Polymer brushes are long stringy molecules that are chemically bonded to a surface to form dense, thin coatings that drastically change the properties of the surface. These coatings guide the behavior of cells for regenerative medicine, promote biocompatibility in implant devices, resist deposition of micro-organisms on ship hulls, or control flow of electricity in microelectronic devices. The structure of the polymer brushes provides the needed mechanical strength to form a stable coating and their chemistry provides the right functionality to interface/communicate between the substrate and the environment. This research program will develop new synthetic methodologies to make these polymer brushes and develop materials characterization techniques to promote a molecular-level understanding of the resulting structures. This methodology has the potential to be of broad impact since the chemistry is simple enough to be adapted by the coatings industries. The research program will serve to inspire and involve undergraduate students in polymer science and engineering research, by working with the PI and graduate student mentors through the REU program. K-12 educational modules developed through this research will be disseminated nationally by the PI and the graduate students by partnering with UW-Madison Institute for Chemical Education (ICE). Through the Women in Science and Engineering (WISE) Residential Program the PI will engage in mentoring underrepresented students to create a supportive environment by coordinating information, research and activities for and about women in the sciences and engineering.TECHNICAL SUMMARY: The research program will study the synthesis of a single-component crosslinked coating to grow homopolymers and mixed polymer brushes with excellent control over homogeneity of grafting sites, dispersities, chemical functionalities, graft to graft distance, ability to grow low to high molecular weights, and with stability to thermal annealing conditions. The growth of polymer brushes from these coatings is fundamentally different from growth from traditional self-assembled monolayers. A key aspect of this research will be to develop a mechanistic understanding of the growth process by combining depth profiling and angle resolved X-ray photoelectron spectroscopy (ARXPS) studies. The stratification effect as well as brush growth kinetics will be studied as a function of crosslink density and coating thickness by embedding specific elemental markers in the brush (Br and N). Combination of ARXPS, Atomic force microscopy and 3D tomography will provide useful morphological information on these polymer brushes. The brushes grown from these coatings will be floated off from the substrate as "polymer carpets" and 3D morphological insight obtained by 3D tomography. Melt self-consistent field theory (SCFT) predictions of phase diagrams for mixed polymer brushes are based on the assumption that the grafting densities are uniform. So far experimental means for meeting these assumptions have lagged behind. Using the unique chemistry for growth of well-defined brushes and the characterization methods developed in this proposal the SCFT predictions will be tested. Furthermore the simplicity of the chemistry is expected to allow arbitrary changes in composition to tune surface properties by incorporating appropriate comonomers. For these reasons the methodology developed here has the potential to have major impact by highly simplifying the way polymer brushes are grown.