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

摘要CTS-0203183 Jennings，G.KaneWeinstein，Randy DVanderbilt University解释：在二氧化碳中形成环境友好的自组装单分子膜和表面引发的聚合物膜这项合作研究将调查环境友好型二氧化碳(CO2)作为溶剂在表面引发法生长的自组装单分子膜(SAM)和超薄聚合物膜的形成中的使用。由于分子尺寸小，与金等金属表面的相互作用很弱，CO2是促进密集堆积、高度结晶的自组装膜形成的近乎理想的溶剂，该项目的作者最近报道了这一点。进一步的研究将考察部分氟化的烷硫醇在金表面形成自组装膜，以及共溶剂对单层膜结构和阻隔性能的影响。本研究还首次尝试将反射吸收红外光谱(RAIRS)和电化学阻抗谱(EIS)分别获得的自组装膜的表面平均结构和势垒性质与扫描探针显微镜(SPM)测定的磁区尺寸和缺陷含量等微观性质相关联。这项研究还将开发一类新的表面引发的、基于多同源共聚合成过程的活性聚合物薄膜。该膜由端硼的SAM引发，并且具有可选择聚合物膜的端基以产生多种表面组合物的有趣的性质。在这些薄膜的生长过程中，前体分子必须在生长的薄膜中扩散，并在活性硼位置发生反应，这样，促进前体分子通过薄膜的传输的溶剂将增加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，因为它能够溶胀许多聚合物，其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，在此聚合过程中使用二氧化碳可以实现简单得多的一锅合成过程，有机溶剂必须在干箱中进行多次溶剂转移。到目前为止，还没有关于使用二氧化碳形成表面引发聚合物膜的研究，只有一项涉及在二氧化碳中形成自组装膜的研究。该项目的成功完成将为通过环境友好的工艺形成这些具有重要技术意义的超薄膜提供新的战略。此外，该项目应加强二氧化碳中材料加工的知识基础，并促进二氧化碳在研究和工业中的更多使用。

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.