Dynamic Mechanically Interlocked Rotaxane and Catenane Catalysts for Isoselective Ring Opening Polymerisation

用于同选择性开环聚合的动态机械联锁轮烷和链烷催化剂

• 批准号: 2329690
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2329690
• 关键词: Dynamic; Mechanically; Interlocked; Rotaxane; Catenane

Polymers consist of long chains comprised from many repeating smaller molecules, known as monomers. Essential in modern life, polymeric materials have extensive applications such as clothing, electronics and medicine, as their desired physical and chemical properties can be engineered by careful monomer selection. However, many polymeric materials are produced from non-renewable monomers and are non-biodegradable, raising serious environmental concerns over their future manufacture and disposal. Consequently, there is mounting public and academic interest in developing more environmentally sustainable routes to biodegradable polymers.Polymer production requires catalysts, most commonly containing metals, to affect regulated linking of the monomer units to form the polymer chain. The environment of the metal in the catalyst, dictated by the arrangement of atoms surrounding it, plays a key role in specifying catalyst performance and selectivity. Such control is essential to form materials with well-defined properties, such as strength and temperature resistance, crucial for any given application.Recent studies demonstrated that incorporating a metal into complex molecular architectures dramatically influences its catalytic behaviour. Mechanically interlocked molecules consist of two components, which are inseparable from each other, but not directly connected e.g. akin to links in a chain. Components bound in this manner are said to be linked by a mechanical bond. The forced proximity of interlocked components allows for powerful interactions between them which are not observed in non-interlocked structures. Furthermore, the unique three-dimensional spatial arrangement of the components of the interlocked structure can be designed to form a host cavity into which a monomer unit binds, increasing its potential reactivity to polymerisation by placing it in a well-defined reactive environment. Such an interlocked catalyst mimics the spatially defined active sites of enzymes. Indeed, a range of interlocked structures have been shown to be catalytically active, displaying enhanced selectivity for various organic reactions compared to non-interlocked catalyst analogues. Despite this, with one exception, mechanical bonding has not been exploited for polymerisation catalysis.This project seeks to build upon on those preliminary results, exploring the relationship between the structure of mechanically interlocked catalysts and polymer properties in order to develop a family of such catalysts for the formation of sustainable polymers. Many conventional catalysts feature multiple catalytic components, typically either by binding two metal atoms in a rigid framework, or through the addition of a second co-catalyst to the mixture. This project will seek to demonstrate an unprecedented strategy of developing mechanically bound catalysts where all requisite components are incorporated in a single molecule. This unique approach uses the spatial constraints of interlocked systems to hold the components of the catalyst in close proximity, without using the rigid frameworks often found in two-centred catalysts. In addition, control over the relative proximity of the interlocked components may enable catalysis to be switched on-and-off selectively or for the reactivity of the catalyst to be modified on-demand, for instance by shielding and exposing different reactive sites on a catalyst framework. Switchability will allow for 'designer polymers', facilitating exquisite control over polymer constitution and properties to produce highly desirable polymeric materials derived from renewable and biodegradable monomer sources. This project falls within the EPSRC Manufacturing the Future, Catalysis and Synthetic Supramolecular Chemistry research areas.

聚合物由许多重复的小分子组成的长链组成，称为单体。聚合物材料在现代生活中必不可少，在服装、电子和医药等领域有着广泛的应用，因为它们所需的物理和化学性能可以通过仔细选择单体来实现。然而，许多聚合物材料是由不可再生的单体生产的，并且是不可生物降解的，这引发了对其未来制造和处置的严重环境问题。因此，公众和学术界对开发更环保的可生物降解聚合物的途径越来越感兴趣。聚合物的生产需要催化剂，最常见的是含有金属，以影响单体单元的调节连接，以形成聚合物链。催化剂中金属的环境由其周围原子的排列决定，在规定催化剂的性能和选择性方面起着关键作用。这种控制对于形成具有明确性质的材料是必不可少的，例如强度和耐温性，这对任何给定的应用都是至关重要的。最近的研究表明，将金属加入复杂的分子结构中会显著影响其催化行为。机械联锁的分子由两个成分组成，它们彼此不可分割，但并不直接相连，例如，类似于链中的链接。以这种方式绑定的组件被认为是通过机械结合连接的。联锁部件的强制接近允许它们之间的强大相互作用，这在非联锁结构中是看不到的。此外，互锁结构组件的独特三维空间布置可以设计成形成单体单元结合到其中的主体腔，通过将其放置在明确定义的反应环境中来提高其对聚合的潜在反应性。这种互锁催化剂模拟了酶在空间上定义的活性部位。事实上，一系列互锁结构已被证明具有催化活性，与未互锁的催化剂类似物相比，对各种有机反应显示出更高的选择性。尽管如此，除了一个例外，机械键合还没有被用于聚合催化剂。本项目试图在这些初步结果的基础上，探索机械互锁催化剂的结构和聚合物性能之间的关系，以开发一系列这样的催化剂，以形成可持续的聚合物。许多传统催化剂具有多个催化成分，通常通过将两个金属原子结合在刚性框架中，或通过向混合物中添加第二个助催化剂来实现。该项目将寻求展示一种前所未有的开发机械结合催化剂的战略，在这种催化剂中，所有必需的成分都被结合到一个分子中。这种独特的方法使用互锁系统的空间限制来将催化剂的组件保持在非常接近的位置，而不使用通常在双中心催化剂中发现的刚性骨架。此外，例如通过屏蔽和暴露催化剂骨架上的不同反应部位，对互锁组分的相对接近程度的控制可以使催化选择性地开启和关闭，或者使催化剂的反应性按需改变。可切换性将允许“设计者聚合物”，便于对聚合物组成和性能进行精细控制，以生产来自可再生和可生物降解单体来源的高度理想的聚合物材料。该项目属于EPSRC制造未来、催化和合成超分子化学研究领域。