Resumen de Physico-chemical phenomena in soft monolayers: chiral recognition, microfluidics and protein interactions
Alba Pulido Companys
In this thesis, several physico-chemical phenomena occurring at the two-dimensional environment of a Langmuir monolayer are studied. In the first section, the characterization of Langmuir monolayers of an azobenzene derivative is presented, together with the induction of chirality by the action of a chemical and a physical force, inside labile condensed domains formed by the trans isomer. This has been compared with results of another study done in the group for a homologue azobenzene molecule. In addition, we have studied a heterochiral recognition phenomenon in monolayers by means of the interaction of two enantiomeric chiral azobenzene derivative surfactants. The following section focuses on the field of two-dimensional microfluidics, and encompasses the analysis of different transport processes occurring at the interface between two monolayers that are coflowing through a channel. In this context, studies of the diffusion between co-flowing monolayers have resulted in a slight increase in the diffusion coefficient value for experiments with curvilinear channels, and when vortices are introduced in the system. In contrast, increasing the concentration gradient between co-flowing monolayers has not been successful at producing a noticeable impact in the measured diffusion coefficient values. On the other hand, a two-dimensional dissolution process has been visualized, with a rate that follows a classic dissolution model. Different unsuccessful attempts to realize a chemical reaction between coflowing monolayers are presented. Moreover, we have addressed the flow of monolayers in open microchannels driven by surface tension gradients, determining that drag at the interface and lateral confinement result in the formation of backflow patterns that carry the subphase liquid upstream through self-organized micro-ducts. This backflow patterns depend on channel geometry and are bound by velocity stagnation surfaces, whose shape and location has been related to the interfacial velocity profiles by means of the combination of a simple model and particle image velocimetry measurements. In the last section, we adapt the protocols used in two-dimensional microfluidics to study the insertion and diffusion of a protein in a phospholipid monolayer.
