EXPLORATORY: Environmentally Friendly Formation of Self-Assembled Monolayers and Surface-Initiated Polymer Films in Carbon Dioxide

詹宁斯，G. KaneWeinstein，兰迪·范德比尔特大学探索：二氧化碳中自组装单层膜和表面引发聚合物薄膜的环境友好形成本合作研究将研究使用环境友好的二氧化碳（CO2）作为溶剂，在表面引发工艺中形成自组装单层膜（SAMs）和超薄聚合物薄膜。由于其小分子尺寸和与金属表面（如金）的弱相互作用，CO2是一种几乎理想的溶剂，可以促进形成密集的、高结晶的sam，正如该项目的作者最近报道的那样。进一步的研究将研究部分氟化烷硫醇在金上形成sam，以及共溶剂对单层膜结构和阻隔性能的影响。本研究还试图首次将反射-吸收红外光谱（RAIRS）和电化学阻抗光谱（EIS）分别获得的sam的表面平均结构和势垒性质与扫描探针显微镜（SPM）确定的畴大小和缺陷含量等微观性质联系起来。本研究还将开发一类基于多同源合成工艺的表面引发的活性聚合物薄膜。这些薄膜是由端有硼的SAM引发的，并且具有一个有趣的特性，即聚合物薄膜的末端基团可以被选择来产生各种各样的表面组合物。在这些薄膜的生长过程中，前驱体分子必须在生长的薄膜中扩散并在活性硼位点发生反应，因此溶剂可以增强前驱体通过薄膜的运输，从而提高薄膜的生长速度和薄膜的最终厚度。二氧化碳是促进这些新型聚合物薄膜生长的潜在有效溶剂，因为它具有使许多聚合物膨胀的能力，它的低粘度和零表面张力，以及许多小分子在二氧化碳中的高扩散速率。此外，与使用有机溶剂相比，在这种聚合过程中使用二氧化碳可以实现更简单的一锅合成过程，而有机溶剂必须在干燥箱中进行多次溶剂转移。到目前为止，还没有关于使用CO2形成表面引发聚合物薄膜的研究，只有一项研究涉及在CO2中形成sam。该项目的成功完成将为通过环保加工形成这些技术上重要的超薄膜提供新的策略。此外，该项目应加强在二氧化碳中加工材料的知识基础，并促进在研究和工业中增加使用二氧化碳。

AbstractCTS-0203183Jennings, G. KaneWeinstein, Randy DVanderbilt UniversityEXPLORATORY: Environmentally Friendly Formation of Self-Assembled Monolayers and Surface-Initiated Polymer Films in Carbon DioxideThis collaborative research will investigate the use of environmentally benign carbon dioxide (CO2) as a solvent in the formation of self-assembled monolayers (SAMs) and ultrathin polymer films grown by a surface-initiated process. Due to its small molecular size and weak interaction with metal surfaces such as gold, CO2 is a nearly ideal solvent to promote the formation of densely packed, highly crystalline SAMs, as recently reported by the authors of this project. Further research will examine the formation of SAMs onto gold from partially fluorinated alkanethiols and the effect of co-solvent on the structure and barrier properties of monolayer films. This research also seeks to correlate for the first time the surface-averaged structure and barrier properties of SAMs as obtained by reflectance-absorption infrared spectroscopy (RAIRS) and electrochemical impedance spectroscopy (EIS), respectively, with their microscopic properties such as domain size and defect content as determined by scanning probe microscopy (SPM). This research will also develop a new class of surface-initiated, living polymer films based on the synthetic process of polyhomologation. The films are initiated from a boron-terminated SAM and have the interesting property that the terminal groups of the polymer film can be selected to create a wide variety of surface compositions. During the growth of these films, the precursor molecules must diffuse through the growing film and react at the active boron site so that solvents that enhance the transport of the precursor through the film will increase the rate of film growth and the ultimate thickness of the films. Carbon dioxide is a potentially effective solvent for enhancing the growth of these novel polymer films due to its ability to swell many polymers, its low viscosity and zero surface tension, and the high diffusion rates of many small molecules in CO2. In addition, the use of CO2 in this polymerization process enables a much simpler one-pot synthetic procedure in contrast to the use of organic solvents that must be conducted with numerous solvent transfers in a dry box. To date, there has been no previous investigation of the use of CO2 in the formation of surface-initiated polymer films and only one other study involving the formation of SAMs in CO2. The successful completion of this project will provide new strategies for forming these technologically important ultrathin films through environmentally friendly processing. Furthermore, this project should enhance the knowledge base for materials processing in CO2 and facilitate the increased use of CO2 in research and industry.