RO and Vacuum

I am wondering, does anyone know if a positive type vacuum pump has been tried with the RO process ?

One reason why I wonder about this is that vacuum, while drawing water molecules through a membrane might allow a water molecule to be less excited.

What is known about water molecules is that when heated or cooled from about 4 degrees Celsius, they expand. What I am wondering is if anyone knows the effect of 40 to 80 bars of pressure on the quantum state of a water molecule compared to it's having a vacuum with the same potential acting on it.

And if so, does temperature's effect change because of vacuum's effect ?