Collaborative Research: Role of Polymer Sequence on Penetrant Transport in Charged Brushes

通过将聚合物接枝到表面而产生的分子级刷可用于控制表面的性质，包括其电荷、润湿性、渗透性和对环境条件（例如作为盐浓度）的响应。原则上，聚合物刷涂表面是药物输送、化学分离过程和水净化中重要应用的潜在变革性技术。选择性地控制小分子和颗粒进出刷子的运输对于这些应用是必要的，但是这样做的能力仍然是一个持续的挑战，因为难以调整刷子的结构。本研究计划将开发一种途径，以控制刷的构象和其对环境条件的反应，通过工程的单体序列组成的聚合物刷。该团队将把工程刷的结构与小分子和颗粒在静态和流动条件下如何通过它们移动联系起来。这项研究将解决一个关键的知识差距，通过提供如何带电单体的顺序影响转运的理解，从而改善水和生物药物纯化的膜涂层。该项目团队将通过当地会议，包括德克萨斯州软物质会议，向休斯顿石化，生物医学和材料行业的科学家和工程师传播这些结果。与此同时，他们还将以休斯顿都会区的多种语言制作水净化教育宣传视频，并在休斯顿能源节上为公众展示动手演示。该项目的目标是从根本上了解聚合物序列对带电聚合物刷内运输的影响。来自休斯顿附近两所大学的团队成员将整合序列控制聚合物合成方面的互补专业知识（Marciel - Rice大学），中子散射应用于刷子（康拉德-休斯顿大学），和最先进的显微镜技术（Marciel和Conrad）提出了三个具体目标：（1）确定聚合物序列对刷性能的作用，（2）确定决定渗透剂和带电聚合物刷动力学之间耦合的机制，（3）了解流动对带电聚合物刷中非平衡渗透剂输运的影响。蛋白质工程方法将被用来合成序列控制的带电聚合物与同位素标记的掠入射小角中子散射（GI-SANS）和中子反射率（NR）的实验，以测量刷构象和高度的平衡和不平衡的条件。渗透传输系数将使用共聚焦和全内反射荧光相关光谱（TIR-FCS）测量，利用垂直灵敏度区分刷内外的传输，并对聚合物基质和多孔介质中的扩散和分散理论进行测试。总之，这些研究将提供新的洞察力的作用，电荷分数和间距的扩散和流动驱动的运输，在充电刷，这将铺平道路，先进的响应surface.This奖项的设计反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Molecular-scale brushes, created by grafting polymers to surfaces, can be used to control the properties of the surface, including its charge, wettability, permeability, and response to environmental conditions such as salt concentration. In principle, polymer brush-coated surfaces are potentially transformative technologies for important applications in drug delivery, chemical separation processes, and water purification. Selectively controlling the transport of small molecules and particles into and out of the brush is necessary for these applications, but the ability to do so remains a persistent challenge because it is difficult to tune the structure of the brush. This research project will develop a route to control brush conformation and its response to environmental conditions by engineering the sequence of monomers that compose the polymer brush. The team will relate the structure of the engineered brushes to how small molecules and particles move through them under static and flow conditions. This research will address a critical knowledge gap by providing understanding of how the sequence of charged monomers affect the transport of penetrants, leading to improved membrane coatings for water and biologic drug purification. The project team will disseminate these results to scientists and engineers in Houston’s petrochemical, biomedical, and materials industries through local meetings, including the Texas Soft Matter Meeting. In parallel, they will develop educational outreach videos on water purification in multiple languages spoken in the Houston metro area, and present hands-on demonstrations for the general public at the Houston Energy Festival.The objective of this project is to develop a fundamental understanding of the influence of polymer sequence on transport within charged polymer brushes. Team members from two nearby universities in Houston will integrate complementary expertise in sequence-controlled polymer synthesis (Marciel – Rice University), neutron scattering applied to brushes (Conrad – University of Houston), and state-of-the-art microscopy techniques (Marciel and Conrad) to address three specific aims: (1) determine the role of polymer sequence on brush properties, (2) identify mechanisms that dictate coupling between penetrant and charged polymer brush dynamics, and (3) understand the effects of flow on out-of-equilibrium penetrant transport in charged polymer brushes. Protein engineering methodologies will be used to synthesize sequence-controlled charged polymers with isotopic labelling for grazing-incidence small angle neutron scattering (GI-SANS) and neutron reflectivity (NR) experiments to measure brush conformation and height in equilibrium and out-of-equilibrium conditions. Penetrant transport coefficients will be measured using confocal and total internal reflection fluorescence correlation spectroscopy (TIR-FCS), exploiting vertical sensitivity to distinguish transport inside and outside brushes and tested against theories for diffusion and dispersion within polymer matrices and in porous media. Together, these studies will provide new insight into the role of charge fraction and spacing on the diffusive and flow-driven transport of penetrants in charged brushes, which will pave the way for the design of advanced responsive surfaces.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.