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Title: New technology for the controlled synthesis of functional materials in flow
Author: Walker, Barnaby
ISNI:       0000 0004 8504 4650
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Functional materials - materials designed to perform a specific function - have many promising, novel properties that are dependent on their structure. Traditional synthetic methods typically do not provide the control and uniformity required to produce these materials in large quantities while maintaining strict control over their structure and pu- rity. Flow chemistry has previously been used to gain improved control over the synthesis of functional materials, but has mostly been applied to single-step syntheses of a limited range of materials. The work carried out in this thesis focused on advancing flow chem- istry technology for the synthesis of high quality functional materials in two key areas: self-optimising reactors, and synthesis in a three-phase flow reactor. In the case of self-optimising reactors, an automated flow reactor was constructed for the synthesis of o-xylenyl functionalised fullerene derivatives. The cascadic nature of the synthesis results in a product consisting of a mixture of desirable and undesirable adducts, therefore making it a good test case for attempting to maximise the formation of one product while suppressing the formation of others. The automated flow reactor developed for this synthesis was composed of self-built components and incorporated in- line product analysis by high performance liquid chromatography. It was able to produce a stable, reproducible product over more than 50 hours, and proved capable of carrying out automated runs comprising over 240 separate measurements. To control the automated flow reactor I developed an intuitive method for optimising competing requirements in a synthesis by formulating chemical optimisations as con- strained optimisations. The requirements of a synthesis were encoded in a figure of merit designed to minimise a lead property while at the same time applying a penalty to viola- tions of constraints on other, competing, properties. After testing different specifications, the synthesis of o-xylenyl functionalised fullerene derivatives was optimised successfully to yield a product with the best balance of the two desirable products, X 2 and X 1 , while suppressing the amount of the least desirable product, X 3 , to below 10 %. Three-phase reactor technology was applied to the controlled synthesis of magnetic iron oxide nanoparticles, via thermal decomposition of Fe(acac) 3 . Although this synthetic route should give more control over nanoparticle size and size uniformity than other syntheses, previous work on adapting it to flow had demonstrated that there was a large problem with reactor fouling due to product deposition in the reaction channel. Three- phase flow was employed to solve this by spacing the reaction droplets out from each other to prevent agglomeration. After changing the reaction solvent to improve the flow characteristics of the reaction mixture, a working three-phase flow synthesis of iron oxide nanoparticles was demonstrated without any fouling.
Supervisor: de Mello, John ; Stavrinou, Paul Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral