![]() The size of the adamantyl group promotes syndiotacticity (or usually does) although I haven't seen NMR proving this one way or the other for this polymer. Did I say "living?" You bet1 and that means you can make controlled molecular weight polymer plus block copolymers, if you so desire.Īnd here's the really interesting fact: the Tg for a 22,000 molecular weight adamantyl polymer is 178 0C! So is the high Tg a result of the "adamantyl effect" or stereoregularity? The answer here is, "Yes!" or "Both," if you want to be picky. And the good news is, despite the bulky adamantane being so near the propagating cation, it undergoes living cationic polymerization quite well. Not so hard to envision (structure is given below). Turns out adamantyl vinyl ether has been made. Well, then, let's talk about the first method, using the right alkyl group. And second, you can make it stereoregular, either isotactic or syndiotactic. That means it's not gooey anymore at temperatures and pressures we would use the polymer at. First, if you have the right alkyl group attached to the oxygen, you can raise Tg above room temperature. What to do? What to do?Īnd what about properties? I said that they were all gooey, sticky messes, right? Not actually true for several reasons. Now everyone's happy, right? Well, happy enough to allow controlled vinyl polymerization but not to give stereoregular polymer. It's not really that simple, but good enough for this discussion. So that leads to the stabilized ionic form of the cation next to a vinyl ether oxygen, one in which one of the oxygen atoms lone pairs is pulled over to form a double bond with the attached carbon. And how's that old saying go? "When push comes to shove. Once that carbocation starts to form, it sucks those elctrons in to help stabilize it.Well, hey, that lazy oxygen wasn't doing anything with its lone pairs anyway. You might think to yourself, "So what? Oxygen is more electronegative than carbon, so how does it help?" Great question, and yes, oxygen is more electronegative, but more important is the fact that it has not one, but two, pairs of electrons just hanging around in its outer shell. Now a propagating carbocation would be located on the carbon next to the ether oxygen. Ok, then, it's time to talk about polymerization of vinyl ethers. Before PVA can hide in a can of paint, we have to react it with NaOH and methanol like this: So what is PVA doing hiding in your paint? PVA is the latex in acrylic latex paint. ![]() One interesting place where PVA likes to hide is in paint cans. The model above is an image of the vinyl ether you can viewīy clicking here or you can just click on the image itself. This is what the monomer isobutyl vinyl ether looks like in 3-D: It's made by free radical vinyl polymerization of the monomer vinyl acetate. PVA is a vinyl polymer, as if you couldn't guess from the name. We'll talk about that kind first, then recent advances that make available some potentially more useful versions. In general, though, they have really lousy properties, mostly being gooey, slimy blobs that are not useful by themselves. The shortest chain versions, such as the methyl ether shown above, are both water and organic solvent soluble. And to be honest, they are structurally similar to poly(vinyl acetate) which is the parent of poly(vinyl alcohol) or PVA. It isn't blatantly obvious where they're found, as is the case with polyethylene or polystyrene. Poly(vinyl ethers), or PVE for short, are members of a family of low-profileīehind-the-scenes polymers with interesting properties. With the 3D model in it when you are ready to come back here.įor Poly(vinyl ether) at a glance, click here! The model above is an image of the methyl vinyl ether polymer.Įither way, be sure to close the new window that opens up Use your mouse on the model to rotate and zoom.Ĭlick items below for other modifications.
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