DS03 - Stimuler le renouveau industriel

Colloidal Assembly In Free Energy Gradients – COATING

Submission summary

Whether we use it to manufacture increasingly complex materials or because our bodies have developed solutions to resist it, drying is a ubiquitous process in our lives. Water has a preponderant role in our world and undergoes a crucial cycle based on phase transitions. Water evaporation occurs as soon as an aqueous system is placed in open air. From a thermodynamic perspective, the system is submitted to a water chemical potential difference and as a result a free energy field builds up at the air/liquid interface. Colloidal systems surround us since they contain a large diversity of species and can thus produce a large array of structures, properties and functions. Their versatility is ensured by weak interactions within the system, typical of soft matter. As a result, colloidal systems are extremely sensitive to free-energy gradients and will typically change dramatically their structuration with the local chemical potential. In project COATING, we investigate the feedback loop operating between transport and structuration, which are coupled during drying of an aqueous system. We will develop a generic experimental methodology to monitor composition and structuration gradients arising through evaporation and relate them to the system’s transport properties. The novelty of the approach rests on a fully quantitative characterization, the implementation of non-ideality in the description of drying, through thermodynamics, and an interdisciplinary approach encompassing drying of complex colloidal dispersions and biointerphases (lung, tear and skin films). We will use drying cells consisting of millifluidic capillary channels placed in a constant chemical potential difference, which is achieved by attaching the channel on one end to a solution reservoir and by exposing the other end to an air flow of controlled relative humidity. Aqueous colloidal systems placed in these cells will undergo controlled evaporation, which will correspond to the build-up of composition and structuration gradients. These gradients will be monitored through a combination of techniques such as Raman and optical microscopy and small-angle X-ray scattering microscopy. Transport will be monitored through mass loss experiments. Non-ideality will be quantified through experimental thermodynamics. This methodology will be applied to two important problems. Firstly, the transition in drying behaviour between simple and complex colloidal dispersions. This complexity notably corresponds to softer particles, colloidal surfaces grafted with polymeric layers or the addition of polymers of surfactant in the aqueous bulk. In practice, real systems of interest to the industry belong to this category of complex systems and this project will thus open new technological developments. Secondly, the study of three biointerphases shielding us from the outside air, the lung film, the skin outer layer and the tear film. We will investigate the structuration of these lipid-based films with relative humidity and notably evaluate the impact of humidity cycles for the lung and tear films and the influence of surfactants on skin. This will shed a new light on self-regulation mechanisms in biological membranes and open new strategies for curing related diseases and optimize formulations.

Project coordination

Kevin ROGER (Laboratoire de Génie Chimique de Toulouse)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


LGC Laboratoire de Génie Chimique de Toulouse

Help of the ANR 277,000 euros
Beginning and duration of the scientific project: March 2018 - 48 Months

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