A flexible polymer-based microfluidic platform to probe asymmetric organocatalytic chemical reactions
Author(s)
Valera del Pino, Fernando Enrique
Type
Thesis
Abstract
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.
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.
Date Issued
2011-08
Date Awarded
2012-01
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Cabral, Joao
Blackmond, Donna
Creator
Valera del Pino, Fernando Enrique
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)