Tailored Molecular Transport In Low-Dimensional Hybrid Materials From 1D Nanocrystals And 2D Nanosheets

精细化学、药物研究和其他复杂纯化过程中的许多重要应用依赖于从溶液和悬浮液中有效分离分子的分离过程。目前的无定形聚合物或纸基膜具有随机形态、控制不良的孔隙率，并且缺乏机械强度。使用这些材料平衡膜的渗透性和选择性性能也具有挑战性。这些综合因素限制了无定形聚合物和纸基膜在高压应用中用于快速有效的分子分离的效用。具有不同孔径、形状和表面化学性质的多孔聚合物材料的随机形态使得难以合理地设计分子输运性质。因此，本项目将研究具有长程有序低维结构元素的膜的分子传输现象和材料特性，以推进基础知识并开发使用纤维和二维材料的新膜。此外，该研究项目将为来自不同背景的研究生和本科生提供跨学科研究培训机会，帮助他们为行业职业做好准备。格鲁吉亚理工学院的本科生也将受益于研究者的软纳米材料课程开发工作。该项目的最终研究目标是了解具有有序纳米通道和纳米片以及快速和各向异性选择性的高度有序的一维和二维（1D和2D）纳米结构中的方向，空间和尺度依赖的分子传输原理。这样的介质可以潜在地用于离子、有机分子、甚至在从纳滤和超滤方案过渡的中间区域内的手性物质的基于膜的分离。该研究将探索诸如材料的组织孔隙率，孔形状和方向（通道状或狭缝状），窄尺寸分布以及潜在的手性偏置相互作用等因素，以调整分子传输和膜分离性能。第一个研究目标是合成纳米晶体和纳米片，并修改材料的表面，以定制它们的组织，表面化学和结构间的相互作用，实现有序的形态与受控的孔组织。第二个目标是制造具有有组织的螺旋和堆叠结构的坚固的膜。该膜将使用化学改性的针状（1D）纤维素纳米晶体和2D碳化钛纳米片与手性组织和定制的孔隙率形状和取向，间距长度和局部手性。将使用溶液中的一组常见染料评估性能。第三个目标是表征有组织的低维材料的内部纳米级组织、孔隙率、取向和机械性能。这些信息可以应用于控制本地和全球的分子纳米尺度的运输，通过缩短曲折，定向通道，和手性偏置，因此，用于研究选择的金属离子，染料和手性分子的运输。该项目将产生在有组织的多相膜与长距离有组织的纳米和纳米片组件的复杂传输现象的深刻的基本理解;这些知识对于设计具有高渗透性，选择性，该奖项反映了NSF的法定使命，并通过使用基金会的知识产权进行评估，被认为值得支持。优点和更广泛的影响审查标准。

Many important applications in fine chemistry, pharmaceutical research, and other sophisticated purification processes rely on separation processes that effectively separate molecules from solutions and suspension. Current amorphous polymer- or paper-based membranes have random morphologies, poorly controlled porosities, and lack mechanical strength. Balancing the membrane’s permeance and selectivity performance using these materials is also challenging. These combined factors limit the utility of amorphous polymer- and paper-based membranes for fast and effective molecular separations in high-pressure applications. The random morphology of porous polymeric materials with varied pore sizes, shapes, and surface chemistries makes it difficult to rationally design molecular transport properties. Therefore, this project will examine the molecular transport phenomena and materials properties of membranes with long-range ordered low-dimensional structural elements to advance fundamental knowledge and develop new membranes using fibrous and two-dimensional materials. Additionally, this research project will provide graduate and undergraduate students from diverse backgrounds with interdisciplinary research training opportunities, helping prepare them for careers in industry. Undergraduate students at Georgia Tech will also benefit from the investigator’s soft nanomaterials curriculum development efforts.The ultimate research goal of this project is to understand the principles of directional, spatial, and scale-dependent molecular transport in highly organized one- and two-dimensional (1D and 2D) nanostructures with ordered nanochannels and nanosheets as well as fast and enantiotropic selectivity. Such media can potentially be used in membrane-based separations of ions, organic molecules, and even chiral species within the intermediate region at the transition from the nanofiltration and ultrafiltration regimes. The research will explore factors such as the materials’ organized porosity, pore shapes and orientation (channel-like or slit-like), narrow size distribution, and potential chiral-biased interactions to tailor molecular transport and membrane separation performance. The first research objective is synthesizing nanocrystals and nanosheets and modifying the materials’ surfaces to tailor their organization, surface chemistries, and inter-structural interactions, achieving ordered morphologies with controlled pore organization. The second objective is fabricating robust ultrathin membranes with organized helicoidal and stacked structures. The membranes will be fabricated using chemically modified needle-like (1D) cellulose nanocrystals and 2D titanium carbide nanosheets with chiral nematic organization and tailored porosity shape and orientation, pitch length, and local chirality. The performance will be assessed using a set of common dyes in solution. The third objective is to characterize the organized low-dimensional materials' internal nanoscale organization, porosity, orientation, and mechanical performance. This information can be applied to control local and global molecular-nanoscale transport through shortened tortuosity, directional channels, and chiral bias and, thus, for studying the transport of select metal ions, dyes, and chiral molecules. The project will yield a deep fundamental understanding of the complex transport phenomena in organized multiphase membranes with long-range organized nanocrystal and nanosheet assemblies; such knowledge is essential to the design of mechanically robust molecular separation membranes with high permeance, selectivity, and rejection rate.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.