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Title: A flexible polymer-based microfluidic platform to probe asymmetric organocatalytic chemical reactions
Author: Valera del Pino, Fernando Enrique
ISNI:       0000 0004 2711 6716
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Microfluidic technologies have been supported by the development of rapid-prototyping techniques that allow for the swift and inexpensive fabrication of customised devices. However, the limited chemical compatibility of microchips has hitherto limited microfluidic organic chemistry research. This thesis reports the development of a comprehensive rapid-prototyping microfluidic platform suitable for kinetic and mechanistic investigations of organic reactions. A lithographic method based on the frontal photopolymerisation (FPP) of thiol-ene resists was employed due to its remarkable solvent compatibility and 3D versatility. The FPP process was investigated and found to exhibit an interfacial instability in addition to planar frontal growth used in device fabrication. This behaviour suggested applications for one-step 3D micropatterning. Systematic studies elucidated the nature of these patterns, which were found to derive from a gel-layer swelling process. The phenomenon was effectively employed to generate 3D structures via a "lock-in" mechanism of interfacial deformation. A microreactor fabrication and operation protocol was then developed for organic reaction studies, assisted by fluid mechanics calculations of residence time distributions and reaction kinetics. The work then focused exclusively on the chemistry of three selected asymmetric organocatalytic reaction systems. A full kinetic study on the non-linear effects in the alkylation of benzaldehyde was carried out in microflow and results were validated against batch studies. Kinetic investigations of an aldol reaction system then helped debunk published claims about enhanced yields and selectivities inside microreactors. Finally, the microfluidic platform was used to investigate the Soai reaction in both single and segmented two-phase flows. This is a unique system exhibiting spontaneous chiral symmetry breaking. The stochastic behaviour of the uncatalysed reaction nonwithstanding, the methodology provided clear profiles of the temporal evolution of enantiomeric amplification. All the results obtained with the microfluidic platform successfully demonstrated the capabilities of the methodology for organic chemistry laboratory studies.
Supervisor: Cabral, Joao ; Blackmond, Donna Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral