I've seen some phase diagrams and I found really interesting, how many exotic solid phases of most elements exist on higher pressure and temperature.

But I've seen always only a single liquid phase and also only a single gaseous phase.

The second is understable, but the first not. I think, if there is an unconventional potential energy field between the molecules, maybe it is not impossible.

Does any chemical compounds with multiple liquid phases exist?

If not, why not?