CONTEXT

The sol-gel process is well known in the prior art, simple to implement, takes place under mild conditions and facilitates the shaping of materials.
In a standard fashion, the sol-gel process consists of a hydrolysis and condensation process which, starting with a molecular precursor (true solution) leads to the formation of a colloidal solution (or sol) then, by connection of the colloidal particles, to the formation of a continuous solid skeleton named a gel.
The non-hydrolytic sol-gel process is a particular case of a sol-gel process, taking place in the absence of water. Another notable particular case consists of a sol-gel process for obtaining silica gels by using formic acid (formation of water in situ) (Sharp, 1994; Dai, 2000).
Ionic Liquids have remarkable properties such as zero volatility, a high ionic conductivity as well as catalytic properties. They are currently used in numerous fields, in particular as electrolytes.
Inventors have decided to combine properties of silica gels and ionic liquids.

TECHNICAL DESCRIPTION

The invention describes a one-step process consisting in preparing a new ionic conductive gel in solid form known as ionogel. The method consist in a step of mixing an ionic liquid with at least one molecular precursor containing at least one hydrolysable group, if necessary in the presence of an acid such as carboxylic acid. The mixture is subsequently left to stand for one or more days until a gel is formed by polycondensation of the molecular precursor(s). The gel contains the aforementioned ionic liquid and can be set in particular in transparent monolithic solid form.

BENEFITS

The invention relates to ionogels, having the following characteristics and advantages:
They are monolithic solids;
They are stable to temperature of approximately 350°C;
They are transparent;
They are ionic conductors their ionic conductivity being in particular comprised between approximately 10-4 and 10-3 S.cm-1 at ambient temperature and between 10-2 and 10-1 S.cm-1 at 230 °C.

INDUSTRIAL APPLICATIONS

Applications for this invention are manifold. This new gel can be used as electrolyte in fuel cells and batteries as it has a very good ionic conductivity and it is stable at high temperature.
It also can be used in optical display thanks to its transparence.

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