Computational and Experimental Design of Associating Bottle Brush Mesostructures

化学系的大分子、超分子和纳米化学计划通过这一奖项资助康涅狄格大学的道格拉斯·H·亚当森教授和埃琳娜·多米多托娃教授在中尺度上研究定义明确的聚合物结构的行为。介观尺度的物质，其特征长度介于纳米尺度(蛋白质、DNA、病毒)和宏观尺度(细菌、染色体、人类头发)之间，通常表现出与较大或较小长度尺度上的根本不同的相互作用和性质。在介观尺度上，材料不仅通过小分子中的化学键结合在一起，而且通过额外的缔合和解离作用力或相互作用而结合在一起。许多生物学活动都是在介观尺度上进行的，存在这些额外的成键作用。例子包括蛋白质折叠、病毒包裹、软体动物外壳的形成和细胞膜之间的运输。在这项研究中，化学反应被用来制备聚合物刷或蠕虫状分子，其中主高聚物链被接枝到不同密度的附加高聚物链上。这些侧链聚合物含有不同的缔合基团，包括DNA链和可以结合金属的小分子。然后使用计算机建模和各种其他测量技术来预测、指导和表征介观尺度上的聚合物刷子的组装。对更广泛的社会的好处包括有可能加速发展基于受控和可预测的中尺度结构的无机/有机和生物启发材料。人力资源和培训效益通过培训不同的本科生和研究生群体以及通过支持化学奇才计划而产生。化学奇才计划与代表不足的人群中的高中生合作，并使用基于竞争的方法来增加对基于STEM的职业的兴趣。在计算机建模的指导下，这项研究正在为介观组装开发独特的构建块。采用已建立的和改进的合成方法相结合的方法，系统地制备了不同缔合基团的聚合物瓶刷，包括用于金属-配体络合的不同密度和不同缔合基团分布的DNA链和配体。用透射电子显微镜和散射方法以及蒙特卡罗和粗粒分子动力学模拟方法对瓶刷聚合物的自组装进行了表征和研究。还系统地研究了瓶刷结构(刚性、接枝长度、官能团的分布和密度)、缔合强度和官能团相互作用的性质(自作用和互补组装)对溶液中自组装的动力学和结果的影响。这项工作解决了与在介观尺度上组装的聚合物材料有关的许多挑战，包括缺乏理论框架，在理解集体相互作用和结构产生的运动方面的差距，在亚稳态建模和测量方面的挑战，以及在实验上控制这些态的困难。与该奖项相关的结果可能对生物、医学和材料化学的新型聚合物结构的开发有价值。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is funding Professors Douglas H. Adamson and Elena Dormidontova at University of Connecticut to study the behavior of well-defined polymeric structures at the mesoscale. Matter at the mesoscale, with characteristic length between the nanoscale (proteins, DNA, viruses) and macroscale (bacteria, chromosomes, human hair) typically exhibit fundamentally different interactions and properties than at larger or smaller length scales. At the mesoscale, materials are held together not only by the chemical bonds found in small molecules, but by additional associative and dissociative forces or interactions. Much of biology operates at the mesoscale with these additional bonding interactions. Examples include protein folding, virus encapsulation, mollusk shell formation, and transport between cellular membranes. In this research, chemical reactions are used to prepare polymer brushes or worm-like molecules in which the main polymer chain is grafted with additional polymer chains of varying density. These side polymer chains contain different associating groups, including DNA strands and small molecules that can bind metals. Computer modeling and a variety of other measurement techniques are then used to predict, guide and characterize assemblies of polymer brushes at the mesoscale. Benefits to the broader society include the potential for accelerated the development of inorganic/organic and bioinspired materials based on controlled and predictable mesoscale structures. Human resource and training benefits arise through the training of a diverse group of undergraduate and graduate students, as well as through the support of the Chemistry Wizards program. The Chemistry Wizards program works with high school students in under-represented populations and uses a competition-based approaches to increase interest in STEM-based careers.Guided by computer modeling, this research is developing unique building blocks for mesoscopic assembly. Polymer bottlebrushes functionalized by different associating groups, including DNA strands and ligands for metal-ligand complexation with different densities and distributions of associating groups, are systematically prepared using a combination of established and modified synthetic approaches. Self-assemblies of bottlebrush polymers are characterized and studied using transmission electron microscopy and scattering approaches, as well as by Monte Carlo and coarse-grained Molecular Dynamics simulations. The effect of bottlebrush architecture (rigidity, length of grafts, distribution, and density of functional groups), association strength, and nature of functional group interaction (self-interaction and complementary assembly) on the dynamics and outcomes of self-assembly in solution are also systematically investigated. This work addresses many challenges pertaining to polymeric materials which assemble at the mesoscale, including lack of theoretical framework, gaps in understanding collective interactions and motions from which structures emerge, challenges in modeling and measuring metastable states, and difficulty in controlling these states experimentally. Results associated with this award could be valuable in the development of novel polymeric structures for biology, medicine, and materials chemistry.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.