Artificial Molecular Machines and Devices

在光、电或化学试剂的影响下，某些互锁的分子，如链烷和轮烷--由适当匹配的环状和哑铃形组分组成--将在分子水平上进行运动(例如，旋转和直线)，这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大学)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、纳米设备和机器部件的可预测运动之间的关系的基本科学问题。这一合作项目的目标是(I)开发互锁分子(可交换的顺丁烯和轮烷)和互穿超分子(可寻址的假环烷)的模板导向合成(自组装)，作为(2)将它们共价连接到骨架(例如，二氧化硅、轮烷)的NSE研究主题氧化铝)，其(3)合成(自组织)必须在(4)展示这些类机器(超级)分子表达宏观机器的不同类型的相干运动(主要是线性的，但也可能是旋转的)的能力之前建立，当(5)它们被化学物质(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，作为(6)将相干的分子水平运动转换和放大为宏观运动的前奏。该小组的具体目标是从链环中存在的组分的相对机械运动中演示力和运动的传递，通过在纳米级上开发类似于(1)发动机、(2)杠杆、(3)肌肉和(4)阀门的驱动材料和装置，我们设想构建基于两站拟轮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，让半哑铃形组件充当活塞。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。在第三种情况下，我们建议使用一种芳香聚合物将伪轮烷的环状和线状成分嫁接到单独的碳纳米管上，我们已经证明了这种聚合物螺旋状地包裹在碳纳米管周围，以实现人工肌肉和执行器。在最后一个例子中，我们打算在适当大小的二氧化硅气孔的颈部开发分子阀，内衬可以诱导结合和解离(从线上的环)的伪轮烷，使得位于气孔内的客体分子分别被捕获或自由逃逸。拟议的研究计划的预期结果包括(I)能够作为机器操作的新的分子马达的合成，(2)机器的集成电源的合成，(3)机器框架的自下而上和自上而下的集成，(4)对力、摩擦等的新的基本理解，在化学家和工程师的共同努力下，这个高度整合的项目寻求将分子机器从科学上的新奇事物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，并通过社区推广提高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.