The model on the right above is an image of the pdb model
you can view by clicking here
or you can just click on the image itself.
Either way, be sure to close the new window that opens up
with the 3D model in it when you are ready to come back here.
Poly(methyl methacrylate), which lazy scientists call PMMA, is a clear plastic, used as a shatterproof replacement for glass. The clear barrier at the ice rink which keeps hockey pucks from flying in the faces of hockey fans is made of PMMA. The chemical company Rohm and Haas makes windows out of it and calls it Plexiglas®. Ineos Acrylics also makes it and calls it Lucite. Lucite is used to make the surfaces of hot tubs, sinks, one-piece bathtub/shower units, among other things.
When it comes to making windows, PMMA has another advantage over glass. PMMA is more transparent than glass. When glass windows are made too thick, they become difficult to see through. But PMMA windows can be made as much as 13 inches (33 cm) thick, and they're still perfectly transparent. This makes PMMA a wonderful material for making large aquariums, with windows which must be thick in order to contain the high pressure of millions of gallons of water. In fact, the largest single window in the world, an observation window at California's Monterrey Bay Aquarium, is made of one big piece of PMMA which is 54 feet long, 18 feet high, and 13 inches thick (16.6 m long, 5.5 m high, and 33 cm thick).
Methyl methacrylate is just one member of a huge family of
methacrylate esters in which the group attached (R in the figure below)
can be any alkyl group or even aryl group. Both of these kinds can be
further substituted with all kinds of reactive and not-so-reactive groups.
For example, HEMA (below) has an alcohol group attached to the ester unit.
This makes polyHEMA water soluble and allows additional groups to be attached
by converting the alcohol to, say, an ester of something else. Neat!
This is true for the acrylates as well, and this
makes these two families of monomers and their polymers some of the most
widely explored and used of all those available today.
PMMA is also found in paint. The painting on your right, Acrylic
Elf was painted by Pete Halverson with acrylic paints. Acrylic
"latex" paints often contain PMMA suspended in water. PMMA doesn't
dissolve in water, so dispersing PMMA in water requires we use another
polymer to make water and PMMA compatible with each other. To see how we
do this, go visit the poly(vinyl acetate) page.
But PMMA is more than just plastic and paint. Often lubricating oils and hydraulic fluids tend to get really viscous and even gummy when they get really cold. This is a real pain when you're trying to operate heavy equipment in really cold weather. But when a little bit PMMA is dissolved in these oils and fluids, they don't get viscous in the cold, and machines can be operated down to -100 oC (-150 oF), that is, presuming the rest of the machine can take that kind of cold!
PMMA is a vinyl polymer, made by free radical vinyl polymerization from the monomer methyl methacrylate.
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And if that's not weird enough for you, here's a THIRD version of PMMA called "isotatctic." In this isomer, all the groups of one kind are lined up on one side of a planar zig-zag of backbone carbons. And that means all the groups of the other kind are on the opposite side. Contrast that to the syndiotactic version in which the two groups alternate on that imaginary planar zig-zag.
Nature doesn't like that arrangement very much, so the chain twists to relieve the "steric strain" also called "steric interaction." Simply put, the relatively big carboxy methyl groups bang into each other so the chain twists in a way to stop that. And the best way to do that "twist" (remember the dance?) is to form a helical conformation. If you look closely at the pop up 3D version (click on the image below), zoom in and out, rotate it around and about, you'll see the beautiful helix formed. Not bad, Mother Nature. We love you and all your twists and turns.
As you can see from the picture below, the structure of methyl methacrylate kind
of looks like
Massachusetts. But Massachusetts doesn't polymerize, because there's
only one. Here's a better, 3-D look at the monomer methyl methacrylate (on the right):
The model on the right above is an image of the pdb model
you can view by clicking here
or you can just click on the image itself.
Either way, be sure to close the new window that opens up
with the 3D model in it when you are ready to come back here.
PMMA is a member of a family of polymers which chemists call acrylates, but the rest of the world calls acrylics.
Another polymer used as an unbreakable glass substitute is polycarbonate. But PMMA is cheaper!
Other polymers used as plastics include:
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