Ionic liquid-directed self-assembly of block copolymers

点击翻译按钮获取中文摘要

The necessity for sufficient and more developed energy and data storage has triggered emerging research fields over the past two decades in both industry and in academia.Energy storage is vital in this day and age, particularly for storing clean energy produced from renewable resources. Novel materials must be generated to meet this ever-growing demand, and self-assembled block copolymers can be used to generate so-called ionogels (gel materials comprising an ionic liquid (IL) immobilised in a cross-linked polymer matrix) which are a class of materials that offer much promise. The use of ILs offers benefits for energy storage applications due to their unique properties including high ionic conductivity and high thermal & chemical stability.Data storage is another important area in which IL-polymer systems can offer significant advances. According to a 2018 IDC White Paper (US44413318), the Global Datasphere is predicted to increase by 530 per cent to 175 zettabytes (1.75x1023 bytes) between 2018 and 2025. To tackle this astronomical rise, we must produce storage devices with ever-increasing areal density (data storage density). To do this, we must generate nanopatterns with sub-10 nm domains, and strongly segregated block copolymers (BCPs) offer a potential route to such small features. BCPs are polymers synthesised using two or more monomers that are chemically distinct, and they can be arranged in an array of different sequences giving rise to different classifications. A synthetic technique that can be used to develop such BCPs is reversible addition-fragmentation chain transfer (RAFT) polymerisation. Utilising RAFT enables stringent control on the polymerisation process such as controlling the molecular weight and polydispersity such that the resulting polymers are very well-defined. A key advantage of using RAFT is that the process is that the reactions can be carried out using a wide range of functional monomers. There has been increasing interest in RAFT-mediated polymerisation-induced self-assembly (PISA), a technique that will be frequently used in this project to synthesise the desired BCPs. PISA has shown to be advantageous relative to other well established self-assembly routes which customarily involve additional post-polymerization steps.This project will focus on the synthesis and characterisation of BCPs with amphiphilic character in ILs (i.e. containing at least one IL-philic and one IL-phobic block). Importantly, industrially-sourced (BASF) ILs will be used to maximise the commercial relevance of the IL-polymer formulations. Formulations will be developed to induce BCP self-assembly, both in solution (to obtain ionogels for energy storage applications) and in the bulk (to generate ordered materials with very small domain sizes for nanoelectronics). Small-angle X-ray scattering (SAXS) will be an important characterisation technique to determine the size and shape (i.e. the morphologies) of the resulting self-assembled species.Bulk self-assembly requires solvent vapour annealing, thermal annealing or spin casting, and the final observed nanopattern can be dependent on whether an IL is present or absent. Low molecular weight block copolymers that exhibit strong microphase separation have yielded great interest amongst research due to their ability to microphase separate into very small (< 10 nm) domains. Solution self-assembly in the presence of ILs yields ionogels, which vastly improve the mechanical properties of ILs, whilst offering the same optimal properties (e.g. ionic conductivity) and thus have the potential to be used in energy storage applications.