Here, take a look at this Wikipedia page:
Right at the beginning of that page it says:
"Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic... ...and was first brought to market in 1933 by the Rohm and Haas Company, under the trademark Plexiglas. It has since been sold under many different names, including Lucite and Perspex.
They're saying that Plexiglas is made out of PMMA, or polymethyl methacrylate.
Now, look further down on that same Wikipedia page under Artistic and Aesthetic Uses where it says:
"Acrylic paint essentially consists of PMMA suspended in water; however since PMMA is hydrophobic, a substance with both hydrophobic and hydrophilic groups needs to be added to facilitate the suspension."
What they're saying is that acrylic paints consist of extremely tiny blobs of hard clear and colourles Plexiglas (called "binder resins") suspended in water, and that a chemical is added to the paint to keep those tiny particles of plastic in suspension.
Now take a look at this page from the Rohm & Haas Company:
In paint-speak, the term "100% Acrylic" means the binder resins are made out of polymethyl methacrylate and "vinly acrylic" means that the binder resins are made out of polyvinyl acetate, which is often abbreviated to "PVA".
That web page from Rohm & Haas lists the benefits of using paints made with PMMA resins, and point #1.b is that under wet conditions, there is a "minimized chance of peeling and loss of adhesion".
They're saying that if you use a 100% Acrylic paint on the ceiling and walls of a bathroom with a shower that's going to create wet conditions for the paint, the paint isn't less likely to peel off.
However, when most people see paint peeling in a bathroom, expecially on the ceiling and high up on the walls, they attribute the problem to insufficient prep work prior to painting. This is probably the most commonly misdiagnosed problem when it comes to painting.