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.

聚合物由长链组成，长链由许多重复的较小分子（称为单体）组成。聚合物材料在现代生活中至关重要，具有广泛的应用，例如服装、电子和医药，因为它们所需的物理和化学特性可以通过仔细选择单体来设计。然而，许多聚合物材料是由不可再生单体生产的，并且不可生物降解，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途径越来越感兴趣。聚合物生产需要催化剂（最常见的是金属）来影响单体单元形成聚合物链的受控连接。催化剂中金属的环境由周围原子的排列决定，在确定催化剂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特性的材料至关重要，例如强度和耐温性，这对于任何给定的应用都至关重要。最近的研究表明，将金属纳入复杂的分子结构会极大地影响其催化行为。机械联锁的分子由两个组分组成，它们彼此不可分离，但不直接连接，例如类似于链条中的链接。以这种方式结合的组件被认为是通过机械键连接的。互锁组件的强制接近允许它们之间产生强大的相互作用，这在非互锁结构中是观察不到的。此外，互锁结构的组件的独特的三维空间排列可以设计成形成单体单元结合到其中的主体空腔，通过将其置于明确的反应环境中来增加其潜在的聚合反应性。这种互锁催化剂模仿了酶的空间限定活性位点。事实上，一系列联锁结构已被证明具有催化活性，与非联锁催化剂类似物相比，对各种有机反应表现出增强的选择性。尽管如此，除了一个例外，机械键合尚未被用于聚合催化。该项目旨在以这些初步结果为基础，探索机械联锁催化剂的结构与聚合物性能之间的关系，以便开发一系列用于形成可持续聚合物的此类催化剂。许多传统催化剂具有多种催化组分，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种助催化剂来实现。该项目将寻求展示一种史无前例的开发机械结合催化剂的策略，其中所有必需的成分都整合在单个分子中。这种独特的方法利用互锁系统的空间限制将催化剂的组分保持在紧密接近的位置，而不使用二中心催化剂中常见的刚性框架。此外，对互锁部件的相对接近度的控制可以使得催化能够选择性地开启和关闭，或者能够按需改变催化剂的反应性，例如通过屏蔽和暴露催化剂框架上的不同反应位点。可转换性将允许“设计聚合物”，促进对聚合物构成和性能的精确控制，以生产源自可再生和可生物降解单体来源的非常理想的聚合物材料。该项目属于 EPSRC 制造未来、催化和合成超分子化学研究领域。