Dynamic Molecular Switching for Environmentally Adaptive Surfaces

虽然表面通常具有固定的成分，但设计动态表面的能力可以在环境变化时迅速改变其成分，这可以影响几个领域，包括防止表面污染和促进吸附/解吸。该项目将结合实验和分子模拟来设计和表征当外部环境改变时迅速改变其表面组成的分子膜。这种成分的变化将通过同时显示“疏水”和“亲水”成分的分子表面基团来实现。当暴露于空气或非极性溶剂时，疏水组分将定向控制表面，而亲水性组分则在暴露于水时定向占据表面。研究人员将使用这些薄膜来研究新的自清洁和热响应表面。这项计划的外展内容包括为有天赋的中学生提供为期一周的纳米技术强化课程，以及分子建模网络夏令营。这项研究的发现将为研究者教授的选修课提供丰富的设计范例，他们都是屡获殊荣的教师。研究人员将继续成为本科生和研究生的有力导师，包括那些来自代表性不足背景的学生，以推动学生进入科学和工程领域。这个合作项目将结合实验和分子模拟来设计和开发一种能够即时适应环境的分子薄膜。当暴露在一个新的环境中，这些薄膜将通过多功能表面基团的取向变得能量最小化。在第一个目标中，将结合分子模拟和实验来设计、合成和组装一类分子吸附剂，用于制备环境适应性单层膜。使用分子模拟设计框架（MoSDeF）的计算筛选将允许快速筛选已确定的参数空间；有前途的吸附剂，然后将实验合成和组装。在第二个目标中，将深入研究最有前途的薄膜，以最大限度地提高响应幅度，建立界面切换机制，并进一步优化分子设计。在第三个目标中，开发的设计工具将用于构建pH值和热响应表面以及自清洁两栖表面，这些表面可以最大限度地减少外来污染、漏油和抗生物污染。由于这里描述的环境适应仅仅是表面基团的重新定向，这些系统将在暴露于新环境时提供立即响应，以最小化界面自由能，而不像通常研究的材料依赖大分子运动并且仅限于特定溶剂或环境。所提出的材料和表面将基于分子模拟和实验之间的紧密合作来设计，以针对已知的环境线索进行有针对性的适应，例如液体和空气，溶剂和水，不同的pH值或温度之间的持续转变。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

While surfaces generally have fixed compositions, the ability to design dynamic surfaces that rapidly alter their composition when the environment is changed can impact several areas, including prevention of surface contamination and facilitation of adsorption/desorption. This project will combine experiments and molecular simulations to design and characterize molecular films that rapidly change their surface composition when the external environment is altered. This change in composition will be accomplished by molecular surface groups that display both “hydrophobic” and “hydrophilic” components. The hydrophobic components will orient to dominate the surface when exposed to air or a nonpolar solvent, whereas the hydrophilic components will orient to occupy the surface when exposed to water. The investigators will use these films to study new self-cleaning and thermoresponsive surfaces. Outreach for this project includes offering a one-week intensive course on nanotechnology to gifted middle school students and a molecular modeling cybercamp. Discoveries from this research will provide fertile design examples for the elective courses taught by the investigators, who are both award-winning teachers. The investigators will continue to be strong mentors for undergraduate and graduate students, including those from underrepresented backgrounds, to propel students toward careers in science and engineering. This collaborative project will combine experiments and molecular simulations to design and develop a class of molecular films that are instantaneously adaptive to their environment. These films will become energetically minimized when exposed to a new environment through the orientation of multifunctional surface groups. In the first objective, molecular simulations and experiments will be combined to design, synthesize, and assemble a class of molecular adsorbates for preparation of environmentally adaptive monolayer films. Computational screening using the Molecular Simulation Design Framework (MoSDeF) will allow for rapid screening of the identified parameter space; promising adsorbates will then be experimentally synthesized and assembled. In the second objective, the most promising films will be thoroughly investigated to maximize the magnitude of the response, establish the mechanism of the interfacial switching, and further optimize the molecular design. In the third objective, the developed design tools will be used to construct pH- and thermo-responsive surfaces and self-cleaning amphibious surfaces that can minimize adventitious contamination, shed oil, and resist biofouling. Since the environmental adaptation described here is simply a reorientation of a surface group, these systems would offer immediate response to minimize interfacial free energy upon exposure to a new environment, unlike commonly studied materials that rely on macromolecular motion and are restricted to specific solvents or environments. The proposed materials and surfaces will be designed based on a tight collaboration between molecular simulations and experiments for targeted adaptation around known environmental cues, such as continual transitions between liquid and air, solvent and water, different pH values, or temperature.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.