Artificial Molecular Machines and Devices

在光、电或化学试剂的影响下，某些被称为连环烷和轮烷的连锁分子——由适当匹配的环状和哑铃形成分组成——将在分子水平上进行运动（例如，旋转和线性），让人想起宏观机器的运动部件。这种分子马达有望成为制造设备和机器的智能“积木”。来自两个不同机构（加州大学洛杉矶分校和附近的加州理工学院）的化学家和工程师团队将在宏观层面上解决围绕可控分子机器、纳米器件和机器部件可预测运动之间关系的基本科学问题。该合作项目聚焦于NSE纳米级器件和系统架构的研究主题，其目标是：(1)开发模板定向合成（自组装）的互锁分子（可切换的链烷和轮烷）和互穿超分子（可寻址的伪环烷）作为先导；(2)将它们共价连接到框架(例如，二氧化硅；氧化铝)，其(3)合成（自组织）必须在(4)证明这些机器（超级）分子在(5)被化学物质（酸/碱或氧化/还原剂）或电子或光（氧化还原和电子转移过程）激活时表达宏观机器特征的不同种类的相干运动（主要是线性的，也可能是旋转的）的能力之前建立，作为(6)传导和放大相干分子的前奏将运动水平化为宏观运动。该团队的具体目标是通过纳米级的致动材料和装置的开发(1)发动机，(2)杠杆，(3)肌肉和(4)阀门，演示从链烷，轮烷和伪环烷中存在的相对机械运动的力和运动的转导。首先，我们设想构建基于双工位伪烷的超分子二冲程发动机，其中环组件共价放置在适当大小的二氧化硅孔中，留下半哑铃形状的组件作为活塞。在第二个例子中，我们建议设计机械杠杆来放大由合适的分子或超分子机器产生的纳米运动。在第三个例子中，我们建议使用芳香聚合物将假环烷的环和螺纹成分接枝到单独的碳纳米管上，我们已经证明了芳香聚合物可以在碳纳米管周围螺旋缠绕，以实现人造肌肉和驱动器。在最后一个例子中，我们打算在适当大小的二氧化硅孔的颈部开发分子阀，内衬假环紫杉烷，可以诱导其结合和解离（从螺纹上形成环），这样位于孔内的客体分子分别被困住或自由逃逸。拟议研究计划的预期结果包括(1)能够像机器一样运行的新型分子马达的合成，(2)机器集成电源的合成，(3)自下而上和自上而下的机器框架集成，(4)对纳米尺度上的力，摩擦等的新基本理解，以及(5)一群在纳米科学方面具有广阔视野和个人专业知识的学生。化学家和工程师并肩工作，这个高度整合的项目旨在将分子机器从科学好奇心转变为具有技术潜力的功能纳米系统，丰富研究生和本科生的教育，并通过社区外拓展促进公众对纳米科学和技术的认识。

Under the influence of light, electricity, or chemical reagents, certain interlocked molecules, known as catenanes and rotaxanes-which comprise appropriately matched ring and dumbbell-shaped components-will perform motions (e.g., rotary and linear) at a molecular level reminiscent of the moving parts of macroscopic machines. Such molecular motors hold promise as the intelligent" building blocks for the construction of devices and machines. A team of chemists and engineers from two different institutions (UCLA and nearby CALTECH) will address the fundamental scientific issues surrounding the relationships between controllable molecular machines, nanoscate devices, and the predictable movements of machine components at a macroscopic level.The aims of this collaborative project-which focuses on the NSE RESEARCH THEME of Nanoscale Devices and System Architecture-are to (I) develop the template-directed synthesis (self-assembly) of interlocked molecules (switchable catenanes and rotaxanes) and interpenetrating supermolecules (addressable pseudorotaxanes) as a forerunner to (2) attaching them covalently to frameworks (e.g., silica, alumina) whose (3) synthesis (self-organization) must be established prior to (4) demonstrating the abilities of these machine-like (super)molecules to express different kinds of coherent movements (mainly linear but also possibly rotary ones) characteristic of macroscopic machines when (5) they are activated by chemicals (acids/bases or oxidizing/reducing agents) or electrons or light (redox and electron transfer processes) as a prelude to (6) transducing and amplifying the coherent molecular level movements into macroscopic motions.The specific objectives of the team are to demonstrate transduction of force and motion from the relative mechanical movements of the components present in catenanes, rotaxanes and pseudorotaxanes through the development-on the nanoscale level-of actuating materials and devices reminiscent of (1) engines, (2) levers, (3) muscles, and (4) valves.In thc first instance, we envisage constructing supramolecular two-stroke engines based on two-station pseudorotaxanes with the ring component lodged covalently in appropriately-sized silica pores, leaving the semi-dumbbell-shaped component to act as the piston. In the second example, we propose to design mechanical levers to amplify nanometer motions generated by suitable molecular or supramolecular machines. In the third instance, we propose to graft the ring and thread components of pseudorotaxanes onto separate carbon nanotubes using an aromatic polymer which we have demonstrated wraps itself helically around carbon nanotubes in order to realize artificial muscles and actuators. And, in the final example, we intend to develop molecular valves at the necks of suitably-sized silica pores, lined with pseudorotaxanes that can be induced to associate and dissociate (rings from threads) such that guest molecules located within the pores are, respectively, trapped or free to escape.The anticipated outcome of the proposed program of research includes (I) the synthesis of new molecular motors capable of operating as machines, (2) the synthesis of integrated power supplies for the machines, (3) a bottom-up and top-down integration of frameworks for the machines, (4) new fundamental understanding of forces, friction, etc., on the nanoscale, and (5) a group of students with both broad perspectives and individual expertise in nanoscicnce.With chemists and engineers working side-by-side, this highly integrated project seeks to transform molecular machines from being scientific curiosities into functioning nanosystems with technological potential, to enrich the education of both graduate and undergraduate students, and to promote the public awareness of nano-science and technology through community outreach.