[scientizscht (OP)]

Hello

Do you know any solvents that do not evaporate fast? Liquid, solid or gel etc but with small molecule diffusion coefficient similar to water.

Thanks!

[chiralSPO]

Do you want it to evaporate, but slowly?

In this case, something like dimethylformamide (DMF) might work. According to wikipedia (https://en.wikipedia.org/wiki/Dimethylformamide), at 20 °C, it has a vapor pressure of 516 Pa and a viscosity of 0.92 mPa•s. (compare to water, with a vapor pressure of 2300 Pa and a viscosity of 1.00 mPa•s)

If you don't want it to evaporate at all, perhaps an ionic liquid like ethylammonium nitrate could work. It is more viscous (28 mPa•s), but has essentially zero vapor pressure.

[scientizscht (OP)]

Thanks, ideally it should not evaporate at all up to e.g. 40C. Is there any solid/semi-solid/gel? I need it not to escape the container, something like jelly beans or emulsion/Voltaren?

[chiralSPO]

If you want diffusion kinetics to be like those in water, I recommend against a sol, gel, or solid.

The ionic liquid won't evaporate in any significant way for thousands of years at 40°C.